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How to Write a Research Paper Introduction (with Examples)

The research paper introduction section, along with the Title and Abstract, can be considered the face of any research paper. The following article is intended to guide you in organizing and writing the research paper introduction for a quality academic article or dissertation.

The research paper introduction aims to present the topic to the reader. A study will only be accepted for publishing if you can ascertain that the available literature cannot answer your research question. So it is important to ensure that you have read important studies on that particular topic, especially those within the last five to ten years, and that they are properly referenced in this section. 1 What should be included in the research paper introduction is decided by what you want to tell readers about the reason behind the research and how you plan to fill the knowledge gap. The best research paper introduction provides a systemic review of existing work and demonstrates additional work that needs to be done. It needs to be brief, captivating, and well-referenced; a well-drafted research paper introduction will help the researcher win half the battle.

The introduction for a research paper is where you set up your topic and approach for the reader. It has several key goals:

• Present your research topic
• Capture reader interest
• Summarize existing research
• Position your own approach
• Define your specific research problem and problem statement
• Highlight the novelty and contributions of the study
• Give an overview of the paper’s structure

The research paper introduction can vary in size and structure depending on whether your paper presents the results of original empirical research or is a review paper. Some research paper introduction examples are only half a page while others are a few pages long. In many cases, the introduction will be shorter than all of the other sections of your paper; its length depends on the size of your paper as a whole.

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Table of Contents

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The introduction in a research paper is placed at the beginning to guide the reader from a broad subject area to the specific topic that your research addresses. They present the following information to the reader

• Scope: The topic covered in the research paper
• Context: Background of your topic
• Importance: Why your research matters in that particular area of research and the industry problem that can be targeted

The research paper introduction conveys a lot of information and can be considered an essential roadmap for the rest of your paper. A good introduction for a research paper is important for the following reasons:

• It stimulates your reader’s interest: A good introduction section can make your readers want to read your paper by capturing their interest. It informs the reader what they are going to learn and helps determine if the topic is of interest to them.
• It helps the reader understand the research background: Without a clear introduction, your readers may feel confused and even struggle when reading your paper. A good research paper introduction will prepare them for the in-depth research to come. It provides you the opportunity to engage with the readers and demonstrate your knowledge and authority on the specific topic.
• It explains why your research paper is worth reading: Your introduction can convey a lot of information to your readers. It introduces the topic, why the topic is important, and how you plan to proceed with your research.
• It helps guide the reader through the rest of the paper: The research paper introduction gives the reader a sense of the nature of the information that will support your arguments and the general organization of the paragraphs that will follow. It offers an overview of what to expect when reading the main body of your paper.

What are the parts of introduction in the research?

A good research paper introduction section should comprise three main elements: 2

• What is known: This sets the stage for your research. It informs the readers of what is known on the subject.
• What is lacking: This is aimed at justifying the reason for carrying out your research. This could involve investigating a new concept or method or building upon previous research.
• What you aim to do: This part briefly states the objectives of your research and its major contributions. Your detailed hypothesis will also form a part of this section.

How to write a research paper introduction?

The first step in writing the research paper introduction is to inform the reader what your topic is and why it’s interesting or important. This is generally accomplished with a strong opening statement. The second step involves establishing the kinds of research that have been done and ending with limitations or gaps in the research that you intend to address. Finally, the research paper introduction clarifies how your own research fits in and what problem it addresses. If your research involved testing hypotheses, these should be stated along with your research question. The hypothesis should be presented in the past tense since it will have been tested by the time you are writing the research paper introduction.

The following key points, with examples, can guide you when writing the research paper introduction section:

• Highlight the importance of the research field or topic
• Describe the background of the topic
• Present an overview of current research on the topic

Example: The inclusion of experiential and competency-based learning has benefitted electronics engineering education. Industry partnerships provide an excellent alternative for students wanting to engage in solving real-world challenges. Industry-academia participation has grown in recent years due to the need for skilled engineers with practical training and specialized expertise. However, from the educational perspective, many activities are needed to incorporate sustainable development goals into the university curricula and consolidate learning innovation in universities.

• Reveal a gap in existing research or oppose an existing assumption
• Formulate the research question

Example: There have been plausible efforts to integrate educational activities in higher education electronics engineering programs. However, very few studies have considered using educational research methods for performance evaluation of competency-based higher engineering education, with a focus on technical and or transversal skills. To remedy the current need for evaluating competencies in STEM fields and providing sustainable development goals in engineering education, in this study, a comparison was drawn between study groups without and with industry partners.

• State the purpose of your study
• Highlight the key characteristics of your study
• Describe important results
• Highlight the novelty of the study.
• Offer a brief overview of the structure of the paper.

Example: The study evaluates the main competency needed in the applied electronics course, which is a fundamental core subject for many electronics engineering undergraduate programs. We compared two groups, without and with an industrial partner, that offered real-world projects to solve during the semester. This comparison can help determine significant differences in both groups in terms of developing subject competency and achieving sustainable development goals.

Write a Research Paper Introduction in Minutes with Paperpal

Paperpal Copilot is a generative AI-powered academic writing assistant. It’s trained on millions of published scholarly articles and over 20 years of STM experience. Paperpal Copilot helps authors write better and faster with:

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With Paperpal Copilot, create a research paper introduction effortlessly. In this step-by-step guide, we’ll walk you through how Paperpal transforms your initial ideas into a polished and publication-ready introduction.

How to use Paperpal to write the Introduction section

Step 1: Sign up on Paperpal and click on the Copilot feature, under this choose Outlines > Research Article > Introduction

Step 2: Add your unstructured notes or initial draft, whether in English or another language, to Paperpal, which is to be used as the base for your content.

Step 3: Fill in the specifics, such as your field of study, brief description or details you want to include, which will help the AI generate the outline for your Introduction.

Step 4: Use this outline and sentence suggestions to develop your content, adding citations where needed and modifying it to align with your specific research focus.

Step 5: Turn to Paperpal’s granular language checks to refine your content, tailor it to reflect your personal writing style, and ensure it effectively conveys your message.

You can use the same process to develop each section of your article, and finally your research paper in half the time and without any of the stress.

The purpose of the research paper introduction is to introduce the reader to the problem definition, justify the need for the study, and describe the main theme of the study. The aim is to gain the reader’s attention by providing them with necessary background information and establishing the main purpose and direction of the research.

The length of the research paper introduction can vary across journals and disciplines. While there are no strict word limits for writing the research paper introduction, an ideal length would be one page, with a maximum of 400 words over 1-4 paragraphs. Generally, it is one of the shorter sections of the paper as the reader is assumed to have at least a reasonable knowledge about the topic. 2 For example, for a study evaluating the role of building design in ensuring fire safety, there is no need to discuss definitions and nature of fire in the introduction; you could start by commenting upon the existing practices for fire safety and how your study will add to the existing knowledge and practice.

When deciding what to include in the research paper introduction, the rest of the paper should also be considered. The aim is to introduce the reader smoothly to the topic and facilitate an easy read without much dependency on external sources. 3 Below is a list of elements you can include to prepare a research paper introduction outline and follow it when you are writing the research paper introduction. Topic introduction: This can include key definitions and a brief history of the topic. Research context and background: Offer the readers some general information and then narrow it down to specific aspects. Details of the research you conducted: A brief literature review can be included to support your arguments or line of thought. Rationale for the study: This establishes the relevance of your study and establishes its importance. Importance of your research: The main contributions are highlighted to help establish the novelty of your study Research hypothesis: Introduce your research question and propose an expected outcome. Organization of the paper: Include a short paragraph of 3-4 sentences that highlights your plan for the entire paper

Cite only works that are most relevant to your topic; as a general rule, you can include one to three. Note that readers want to see evidence of original thinking. So it is better to avoid using too many references as it does not leave much room for your personal standpoint to shine through. Citations in your research paper introduction support the key points, and the number of citations depend on the subject matter and the point discussed. If the research paper introduction is too long or overflowing with citations, it is better to cite a few review articles rather than the individual articles summarized in the review. A good point to remember when citing research papers in the introduction section is to include at least one-third of the references in the introduction.

The literature review plays a significant role in the research paper introduction section. A good literature review accomplishes the following: Introduces the topic – Establishes the study’s significance – Provides an overview of the relevant literature – Provides context for the study using literature – Identifies knowledge gaps However, remember to avoid making the following mistakes when writing a research paper introduction: Do not use studies from the literature review to aggressively support your research Avoid direct quoting Do not allow literature review to be the focus of this section. Instead, the literature review should only aid in setting a foundation for the manuscript.

Remember the following key points for writing a good research paper introduction: 4

• Avoid stuffing too much general information: Avoid including what an average reader would know and include only that information related to the problem being addressed in the research paper introduction. For example, when describing a comparative study of non-traditional methods for mechanical design optimization, information related to the traditional methods and differences between traditional and non-traditional methods would not be relevant. In this case, the introduction for the research paper should begin with the state-of-the-art non-traditional methods and methods to evaluate the efficiency of newly developed algorithms.
• Avoid packing too many references: Cite only the required works in your research paper introduction. The other works can be included in the discussion section to strengthen your findings.
• Avoid extensive criticism of previous studies: Avoid being overly critical of earlier studies while setting the rationale for your study. A better place for this would be the Discussion section, where you can highlight the advantages of your method.
• Avoid describing conclusions of the study: When writing a research paper introduction remember not to include the findings of your study. The aim is to let the readers know what question is being answered. The actual answer should only be given in the Results and Discussion section.

To summarize, the research paper introduction section should be brief yet informative. It should convince the reader the need to conduct the study and motivate him to read further. If you’re feeling stuck or unsure, choose trusted AI academic writing assistants like Paperpal to effortlessly craft your research paper introduction and other sections of your research article.

1. Jawaid, S. A., & Jawaid, M. (2019). How to write introduction and discussion. Saudi Journal of Anaesthesia, 13(Suppl 1), S18.

2. Dewan, P., & Gupta, P. (2016). Writing the title, abstract and introduction: Looks matter!. Indian pediatrics, 53, 235-241.

3. Cetin, S., & Hackam, D. J. (2005). An approach to the writing of a scientific Manuscript1. Journal of Surgical Research, 128(2), 165-167.

4. Bavdekar, S. B. (2015). Writing introduction: Laying the foundations of a research paper. Journal of the Association of Physicians of India, 63(7), 44-6.

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Writing a Research Paper Introduction (with 3 Examples)

Nail your research paper's introduction! Learn to captivate and inform readers from the start—our guide shows how!

Ertugrul Portakal

Apr 12, 2024

TABLE OF CONTENTS

A catchy and informative introduction is essential in academic writing, especially if you want your readers to have background information about your paper. However, writing an interesting and informative introduction can sometimes be a time-consuming and tiring process. If you don't know where to start when crafting an introduction, no need to worry - we've got you covered!

In this article, we will explain step by step what an introduction is in academic writing and how to write it!

Ready? Let's start!

• An introduction is a paragraph that provides information about your entire paper and aims to attract and inform the reader.
• Before writing an introduction or even starting your paper, you need to research academic sources.
• The first one or two sentences of an introduction paragraph should be a hook to attract the reader's attention.
• Afterwards, you need to prepare the reader for your argument by giving background information about your topic.
• Finally, you should state your argument about your topic with a thesis statement.
• If you are writing a longer paper, you can inform your readers about the map of your paper.
• If you are looking for an AI assistant to support you throughout your writing process, TextCortex is designed for you with its advanced features.

What is an Introduction in a research paper?

In any academic writing, including essays and research papers, an introduction is the first paragraph that the reader will encounter. This paragraph should both attract the reader's attention and give them the necessary information about the paper. In any academic paper, the introduction paragraph constitutes 10% of the paper's total word count. For example, if you are preparing a 3,000-word paper, your introduction paragraph should consist of approximately 300 words. You should also write sentences within these 300 words that will attract the reader's attention and provide them with information about the paper.

Importance of an Introduction Paragraph

The biggest function of an introduction paragraph is to prepare the reader for the author's thesis statement. A traditional introduction paragraph begins with a few sentences or questions that will catch the reader's attention. After attracting the reader's attention, necessary background information on the subject is given. Finally, the author explains to the readers what the whole paper is about by stating the thesis. A thesis statement is the final sentence that summarizes the main points of your paper and conveys your claim.

First Things First: Preliminary Research

When working on any academic writing type, it is essential to start by researching your topic thoroughly before beginning to type. What sets academic writing apart from other writing types is the requirement for it to be written using accurate information from reliable sources.

Researching academic sources can be a time-consuming and unnecessary process. One has to read through hundreds of pages, review dozens of articles and verify the accuracy of each source. However, if you're looking to reduce your workload and maximize efficiency by automating repetitive tasks such as literature review, ZenoChat is the perfect solution for you. With its web search feature, ZenoChat can use the entire internet as a data source. Additionally, by activating the "scholar" option of the ZenoChat web search feature, you can ensure that it only uses academic sources when generating output.

How to Create an Introduction for Academic Writing?

Creating an introduction paragraph that is interesting, informative, and conveys your thesis is an easier process than it seems. As long as you have sufficient information about your topic and an outline , you can write engaging introductions by following a few simple steps. Let's take a closer look at how to write an introduction for academic writing.

1-) Start with a Catchy Hook

Your first sentence is one of the factors that most influence a reader's decision to read your paper. This sentence determines the tone of your paper and attracts the reader's attention. For this reason, we recommend that you start your introduction paragraph with a strong and catchy hook sentence.

• Avoid long and complex sentences
• Use clear and concise sentences
• Write a sentence that will spark the reader's curiosity
• You can ask questions that will encourage the reader to read the remaining paragraph
• Avoid fact or overly broad sentences
• Avoid using dictionary definitions as your hook

2-) Give Background Information

After writing a strong hook sentence, you need to provide basic information about your topic so that the reader can understand what they will learn about when they read your paper. In this section, you can benefit from opinions that support or oppose your argument. Additionally, this section should refer to the body paragraphs of your writing.

• You can write a background information sentence for each body paragraph.
• The information here should be concise and compact
• Avoid talking about your evidence and results unless necessary.

3-) State Your Thesis 

After attracting the reader's attention and providing background information, it is time to present your approach and argument towards the topic with a thesis statement. A thesis statement usually comprises one or two sentences and communicates the paper's argument to the reader. A well-written thesis statement should express your stance on the topic.

• Avoid merely stating a fact
• Claim your argument

4-) Tell Reader About Your Paper

Although you need to move on to body paragraphs after the thesis statement in short papers, it will be useful to add a few sentences that will guide the reader in your longer papers. This way, your readers can better understand which arguments they will encounter on which pages and the course of your paper. That leads the reader to clearly understand and follow your content.

Let’s Wrap it Up

Writing an interesting and informative introduction is usually a long process that requires a lot of rewriting. You may need to rewrite a sentence dozens of times so that your words and sentences clearly describe your paper and argument. Fortunately, you can generate state-of-the-art introductions using AI tools and use them with a little editing.

When it comes to text generation, paraphrasing, and grammar & spelling checking, TextCortex is the way to go with its advanced LLMs and customization options. With TextCortex, you can generate all writing types, including introduction, from scratch, rewrite your existing texts, change their tone of voice, or fix their grammar. TextCortex is available as a web application and browser extension. The TextCortex browser extension is integrated with 30,000+ websites and apps. So, you can complete your AI-driven writing tasks anywhere and anytime.

Let's examine a few sample introductions generated by TextCortex.

Example Introduction #1

“Should social media platforms be banned from collecting their users' data?”

Example Introduction #2

“Do electric vehicles decrease overall emissions?”

Example Introduction #3

“Is graffiti an act of vandalism or the creation of art?”

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How to Write a Research Paper Introduction

As the saying goes, You only get one chance at a first impression, and research papers are no exception. It’s the first thing people read, so a solid research paper introduction should lay the groundwork for the rest of the paper, answer the early questions a reader has, and make a personal impact—all while being as succinct as possible.

It’s not always easy knowing how to write introductions for research papers, and sometimes they can be the hardest part of the whole paper. So in this guide, we’ll explain everything you need to know, discussing what to include in introductions to research papers and sharing some expert tips so you can do it well.

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What is a research paper introduction?

A research paper introduction is an essential part of academic writing that explains the paper’s main topic and prepares the reader for the rest of the paper. After reading the introduction, the reader should know what the paper is about, what point it’s trying to make, and why it matters.

For scientific and data-heavy research papers, the introduction has a few more formal requirements, such as briefly describing how the research was conducted. We’ll explain more on those in the next section.

The role of the research paper introduction is to make sure the reader understands all the necessary preliminary information before they encounter the discoveries presented in the body of the research paper. Learning how to write an introduction is an important part of knowing how to write a research paper .

How long should a research paper introduction be?

There are no firm rules on how long a research paper introduction should be. The only guideline is that the length of the introduction should be commensurate with the length of the entire paper. Very long papers may have an introduction that spans more than one page, while short papers can have an introduction of only a paragraph.

What to include in introductions to research papers

Generally speaking, a good research paper introduction includes these parts:

1 Thesis statement

2 Background context

3 Niche (research gap)

4 Relevance (how the paper fills that gap)

5 Rationale and motivation

First, a thesis statement is a single sentence that summarizes the main topic of your paper. The thesis statement establishes the scope of the paper, defining what will and won’t be discussed.

You also want to provide some background , summarizing what the reader needs to know before you present new information. This includes a brief history of the topic and any previous research or writings that your own ideas are built on.

In academic writing, it’s good to explain the paper’s niche, the area of research that your paper contributes to. In formal research papers, you should describe the research gap, a particular area of a topic that either has not been researched or has inadequate research. Informal research papers without original research don’t need to worry much about this.

After establishing the niche, next you explain how your research paper fills that niche—in other words, your paper’s relevance. Why is this paper important? What does it teach us? In a formal research paper introduction, you explain how your paper and research attempt to close the research gap and add the missing data.

Last, mention the rationale and motivation for why you chose this topic for your research. This can be either a personal choice or a practical one, such as researching a topic that urgently needs new information. You can also mention what you hope your research accomplishes—your goals—to round out your motivations.

What to include in introductions to scientific research papers

Scientific research papers, especially if they present original research and new data, have some additional requirements for their introduction:

• Methodology
• Research question or hypothesis
• Literature review (previous research and current literature)

The methodology describes how you conducted your research, including which tools you used or the procedure for your tests. This is to validate your findings, so readers know your data comes from a reliable source.

A research question or hypothesis acts similarly to the thesis statement. A research question is simply the question your research aims to answer, while a hypothesis is your prediction, made before the experiments begin, of what the research will yield. By the end of the paper, your hypothesis will be proven right or wrong.

Given the nature of scientific papers, the background context is more detailed than in other research papers. A literature review explains all the research on your particular topic that’s relevant to your paper. You outline the major writings and other research papers your own research is based on, and discuss any problems or biases those writings have that may undermine their findings.

The literature review is the perfect place for establishing the research gap. Here you can explain in your own words why the current research on your topic is insufficient, and why your own research serves to fill this gap.

If you’re writing a casual paper that relies only on existing research, you don’t need to worry about these.

How to write introductions for research papers

1 use the cars model.

The English scientist John Swales devised a method known as the CARS model to “Create A Research Space” in introductions. Although it’s aimed at scientific papers, this simple, three-step structure can be used to outline any research paper introduction.

• Establishing a territory : Explain the background context of your topic, including previous research.
• Establishing a niche : Explain that one area of your topic is missing information or that the current research is inadequate.
• Occupying a niche : Explain how your research “fills in” that missing information from your topic.

Swales then suggests stating the outcome of the research and previewing the structure of the rest of the paper, although these don’t apply to all research papers, particularly informal ones.

2 Start broad and narrow down

One common mistake in writing research paper introductions is to try fitting in everything all at once. Instead, pace yourself and present the information piece by piece in the most logical order for the reader to understand. Generally that means starting broad with the big picture, and then gradually getting more specific with the details.

For research paper introductions, you want to present an overview of the topic first, and then zero in on your particular paper. This “funnel” structure naturally includes all the necessary parts of what to include in research paper introductions, from background context to the niche or research gap and finally the relevance.

3 Be concise

Introductions aren’t supposed to be long or detailed; they’re more like warm-up acts. Introductions are better when they cut straight to the point—save the details for the body of the paper, where they belong.

The most important point about introductions is that they’re clear and comprehensible. Wordy writing can be distracting and even make your point more confusing, so remove unnecessary words and try to phrase things in simple terms that anyone can understand.

4 Consider narrative style

Although not always suitable for formal papers, using a narrative style in your research paper introduction can help immensely in engaging your reader and “ hooking ” them emotionally. In fact, a 2016 study showed that, in certain papers, using narrative strategies actually improves how often they’re cited in other papers.

A narrative style involves making the paper more personal in order to appeal to the reader’s emotions. Strategies include:

• Using first-person pronouns ( I, we, my, our ) to establish yourself as the narrator
• Describing emotions and feelings in the text
• Setting the scene; describing the time and place of key events to help the reader imagine them
• Appealing to the reader’s morality, sympathy, or urgency as a persuasion tactic

Again, this style won’t work for all research paper introductions, especially those for scientific research. However, for more casual research papers—and especially essays—this style can make your writing more entertaining or at the very least interesting, perfect for raising your reader’s enthusiasm right at the start of your paper.

5 Write your research paper introduction last

Your introduction may come first in a research paper, but a common tip is to wait on writing it until everything else is already written. This makes it easier to summarize your paper, because at that point you know everything you’re going to say. It also removes the urge to include everything in the introduction because you don’t want to forget anything.

Furthermore, it’s especially helpful to write your introduction after your research paper conclusion . A research paper’s introduction and conclusion share similar themes, and often mirror each other’s structure. Writing the conclusion is usually easier, too, thanks to the momentum from writing the rest of the paper, and that conclusion can help guide you in writing your introduction.

Research paper introduction FAQs

For academic writing like research papers, an introduction has to explain the topic, establish the necessary background context, and prepare the reader for the rest of the paper. In scientific research papers, the introduction also addresses the methodology and describes the current research for that topic.

What do you include in an introduction to a research paper?

A good research paper introduction includes:

• Thesis statement
• Background context
• Niche (research gap)
• Relevance (how it fills that gap)
• Rationale and motivation

Scientific research papers with original data should also include the methodology, a literature review, and possibly a research question or hypothesis.

How do you write an introduction for a research paper?

There are a few important guidelines to remember when writing a research paper. Start with a broad overview of the topic and gradually get more specific with the details and how your paper relates. Be sure to keep your introduction as succinct as possible, as you don’t want it to be too long. Some people find it’s easier to write the introduction last, after the rest of the paper is finished.

Research Paper Introduction Examples

Looking for research paper introduction examples? Quotes, anecdotes, questions, examples, and broad statements—all of them can be used successfully to write an introduction for a research paper. It’s instructive to see them in action, in the hands of skilled academic writers.

Let’s begin with David M. Kennedy’s superb history, Freedom from Fear: The American People in Depression and War, 1929–1945 . Kennedy begins each chapter with a quote, followed by his text. The quote above chapter 1 shows President Hoover speaking in 1928 about America’s golden future. The text below it begins with the stock market collapse of 1929. It is a riveting account of just how wrong Hoover was. The text about the Depression is stronger because it contrasts so starkly with the optimistic quotation.

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“We in America today are nearer the final triumph over poverty than ever before in the history of any land.”—Herbert Hoover, August 11, 1928 Like an earthquake, the stock market crash of October 1929 cracked startlingly across the United States, the herald of a crisis that was to shake the American way of life to its foundations. The events of the ensuing decade opened a fissure across the landscape of American history no less gaping than that opened by the volley on Lexington Common in April 1775 or by the bombardment of Sumter on another April four score and six years later. (adsbygoogle = window.adsbygoogle || []).push({}); The ratcheting ticker machines in the autumn of 1929 did not merely record avalanching stock prices. In time they came also to symbolize the end of an era. (David M. Kennedy, Freedom from Fear: The American People in Depression and War, 1929–1945 . New York: Oxford University Press, 1999, p. 10)

Kennedy has exciting, wrenching material to work with. John Mueller faces the exact opposite problem. In Retreat from Doomsday: The Obsolescence of Major War , he is trying to explain why Great Powers have suddenly stopped fighting each other. For centuries they made war on each other with devastating regularity, killing millions in the process. But now, Mueller thinks, they have not just paused; they have stopped permanently. He is literally trying to explain why “nothing is happening now.” That may be an exciting topic intellectually, it may have great practical significance, but “nothing happened” is not a very promising subject for an exciting opening paragraph. Mueller manages to make it exciting and, at the same time, shows why it matters so much. Here’s his opening, aptly entitled “History’s Greatest Nonevent”:

On May 15, 1984, the major countries of the developed world had managed to remain at peace with each other for the longest continuous stretch of time since the days of the Roman Empire. If a significant battle in a war had been fought on that day, the press would have bristled with it. As usual, however, a landmark crossing in the history of peace caused no stir: the most prominent story in the New York Times that day concerned the saga of a manicurist, a machinist, and a cleaning woman who had just won a big Lotto contest. This book seeks to develop an explanation for what is probably the greatest nonevent in human history. (John Mueller, Retreat from Doomsday: The Obsolescence of Major War . New York: Basic Books, 1989, p. 3)

In the space of a few sentences, Mueller sets up his puzzle and reveals its profound human significance. At the same time, he shows just how easy it is to miss this milestone in the buzz of daily events. Notice how concretely he does that. He doesn’t just say that the New York Times ignored this record setting peace. He offers telling details about what they covered instead: “a manicurist, a machinist, and a cleaning woman who had just won a big Lotto contest.” Likewise, David Kennedy immediately entangles us in concrete events: the stunning stock market crash of 1929. These are powerful openings that capture readers’ interests, establish puzzles, and launch narratives.

Sociologist James Coleman begins in a completely different way, by posing the basic questions he will study. His ambitious book, Foundations of Social Theory , develops a comprehensive theory of social life, so it is entirely appropriate for him to begin with some major questions. But he could just as easily have begun with a compelling story or anecdote. He includes many of them elsewhere in his book. His choice for the opening, though, is to state his major themes plainly and frame them as a paradox. Sociologists, he says, are interested in aggregate behavior—how people act in groups, organizations, or large numbers—yet they mostly examine individuals:

A central problem in social science is that of accounting for the function of some kind of social system. Yet in most social research, observations are not made on the system as a whole, but on some part of it. In fact, the natural unit of observation is the individual person…  This has led to a widening gap between theory and research… (James S. Coleman, Foundations of Social Theory . Cambridge, MA: Harvard University Press, 1990, pp. 1–2)

After expanding on this point, Coleman explains that he will not try to remedy the problem by looking solely at groups or aggregate-level data. That’s a false solution, he says, because aggregates don’t act; individuals do. So the real problem is to show the links between individual actions and aggregate outcomes, between the micro and the macro.

The major problem for explanations of system behavior based on actions and orientations at a level below that of the system [in this case, on individual-level actions] is that of moving from the lower level to the system level. This has been called the micro-to-macro problem, and it is pervasive throughout the social sciences. (Coleman, Foundations of Social Theory , p. 6)

Explaining how to deal with this “micro-to-macro problem” is the central issue of Coleman’s book, and he announces it at the beginning.

Coleman’s theory-driven opening stands at the opposite end of the spectrum from engaging stories or anecdotes, which are designed to lure the reader into the narrative and ease the path to a more analytic treatment later in the text. Take, for example, the opening sentences of Robert L. Herbert’s sweeping study Impressionism: Art, Leisure, and Parisian Society : “When Henry Tuckerman came to Paris in 1867, one of the thousands of Americans attracted there by the huge international exposition, he was bowled over by the extraordinary changes since his previous visit twenty years before.” (Robert L. Herbert, Impressionism: Art, Leisure, and Parisian Society . New Haven, CT: Yale University Press, 1988, p. 1.) Herbert fills in the evocative details to set the stage for his analysis of the emerging Impressionist art movement and its connection to Parisian society and leisure in this period.

David Bromwich writes about Wordsworth, a poet so familiar to students of English literature that it is hard to see him afresh, before his great achievements, when he was just a young outsider starting to write. To draw us into Wordsworth’s early work, Bromwich wants us to set aside our entrenched images of the famous mature poet and see him as he was in the 1790s, as a beginning writer on the margins of society. He accomplishes this ambitious task in the opening sentences of Disowned by Memory: Wordsworth’s Poetry of the 1790s :

Wordsworth turned to poetry after the revolution to remind himself that he was still a human being. It was a curious solution, to a difficulty many would not have felt. The whole interest of his predicament is that he did feel it. Yet Wordsworth is now so established an eminence—his name so firmly fixed with readers as a moralist of self-trust emanating from complete self-security—that it may seem perverse to imagine him as a criminal seeking expiation. Still, that is a picture we get from The Borderers and, at a longer distance, from “Tintern Abbey.” (David Bromwich, Disowned by Memory: Wordsworth’s Poetry of the 1790s . Chicago: University of Chicago Press, 1998, p. 1)

That’s a wonderful opening! Look at how much Bromwich accomplishes in just a few words. He not only prepares the way for analyzing Wordsworth’s early poetry; he juxtaposes the anguished young man who wrote it to the self-confident, distinguished figure he became—the eminent man we can’t help remembering as we read his early poetry.

Let us highlight a couple of other points in this passage because they illustrate some intelligent writing choices. First, look at the odd comma in this sentence: “It was a curious solution, to a difficulty many would not have felt.” Any standard grammar book would say that comma is wrong and should be omitted. Why did Bromwich insert it? Because he’s a fine writer, thinking of his sentence rhythm and the point he wants to make. The comma does exactly what it should. It makes us pause, breaking the sentence into two parts, each with an interesting point. One is that Wordsworth felt a difficulty others would not have; the other is that he solved it in a distinctive way. It would be easy for readers to glide over this double message, so Bromwich has inserted a speed bump to slow us down. Most of the time, you should follow grammatical rules, like those about commas, but you should bend them when it serves a good purpose. That’s what the writer does here.

The second small point is the phrase “after the revolution” in the first sentence: “Wordsworth turned to poetry after the revolution to remind himself that he was still a human being.” Why doesn’t Bromwich say “after the French Revolution”? Because he has judged his book’s audience. He is writing for specialists who already know which revolution is reverberating through English life in the 1790s. It is the French Revolution, not the earlier loss of the American colonies. If Bromwich were writing for a much broader audience—say, the New York Times Book Review—he would probably insert the extra word to avoid confusion.

The message “Know your audience” applies to all writers. Don’t talk down to them by assuming they can’t get dressed in the morning. Don’t strut around showing off your book learnin’ by tossing in arcane facts and esoteric language for its own sake. Neither will win over readers.

Bromwich, Herbert, and Coleman open their works in different ways, but their choices work well for their different texts. Your task is to decide what kind of opening will work best for yours. Don’t let that happen by default, by grabbing the first idea you happen upon. Consider a couple of different ways of opening your thesis and then choose the one you prefer. Give yourself some options, think them over, then make an informed choice.

Using the Introduction to Map out Your Writing

Whether you begin with a story, puzzle, or broad statement, the next part of the research paper introduction should pose your main questions and establish your argument. This is your thesis statement—your viewpoint along with the supporting reasons and evidence. It should be articulated plainly so readers understand full well what your paper is about and what it will argue.

After that, give your readers a road map of what’s to come. That’s normally done at the end of the introductory section (or, in a book, at the end of the introductory chapter). Here’s John J. Mearsheimer presenting such a road map in The Tragedy of Great Power Politics . He not only tells us the order of upcoming chapters, he explains why he’s chosen that order and which chapters are most important:

The Plan of the Book The rest of the chapters in this book are concerned mainly with answering the six big questions about power which I identified earlier. Chapter 2, which is probably the most important chapter in the book, lays out my theory of why states compete for power and why they pursue hegemony. In Chapters 3 and 4, I define power and explain how to measure it. I do this in order to lay the groundwork for testing my theory… (John J. Mearsheimer, The Tragedy of Great Power Politics . New York: W. W. Norton, 2001, p. 27)

As this excerpt makes clear, Mearsheimer has already laid out his “six big questions” in the research paper introduction. Now he’s showing us the path ahead, the path to answering those questions.

At the end of the research paper introduction, give your readers a road map of what’s to come. Tell them what the upcoming sections will be and why they are arranged in this particular order.

Learn how to write an introduction for a research paper .

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How to Write an Introduction for a Research Paper

Table of Contents

Writing an introduction for a research paper is a critical element of your paper, but it can seem challenging to encapsulate enormous amount of information into a concise form. The introduction of your research paper sets the tone for your research and provides the context for your study. In this article, we will guide you through the process of writing an effective introduction that grabs the reader's attention and captures the essence of your research paper.

Understanding the Purpose of a Research Paper Introduction

The introduction acts as a road map for your research paper, guiding the reader through the main ideas and arguments. The purpose of the introduction is to present your research topic to the readers and provide a rationale for why your study is relevant. It helps the reader locate your research and its relevance in the broader field of related scientific explorations. Additionally, the introduction should inform the reader about the objectives and scope of your study, giving them an overview of what to expect in the paper. By including a comprehensive introduction, you establish your credibility as an author and convince the reader that your research is worth their time and attention.

Key Elements to Include in Your Introduction

When writing your research paper introduction, there are several key elements you should include to ensure it is comprehensive and informative.

• A hook or attention-grabbing statement to capture the reader's interest.  It can be a thought-provoking question, a surprising statistic, or a compelling anecdote that relates to your research topic.
• A brief overview of the research topic and its significance. By highlighting the gap in existing knowledge or the problem your research aims to address, you create a compelling case for the relevance of your study.
• A clear research question or problem statement. This serves as the foundation of your research and guides the reader in understanding the unique focus of your study. It should be concise, specific, and clearly articulated.
• An outline of the paper's structure and main arguments, to help the readers navigate through the paper with ease.

Preparing to Write Your Introduction

Before diving into writing your introduction, it is essential to prepare adequately. This involves 3 important steps:

• Conducting Preliminary Research: Immerse yourself in the existing literature to develop a clear research question and position your study within the academic discourse.
• Identifying Your Thesis Statement: Define a specific, focused, and debatable thesis statement, serving as a roadmap for your paper.
• Considering Broader Context: Reflect on the significance of your research within your field, understanding its potential impact and contribution.

By engaging in these preparatory steps, you can ensure that your introduction is well-informed, focused, and sets the stage for a compelling research paper.

Structuring Your Introduction

Now that you have prepared yourself to tackle the introduction, it's time to structure it effectively. A well-structured introduction will engage the reader from the beginning and provide a logical flow to your research paper.

Starting with a Hook

Begin your introduction with an attention-grabbing hook that captivates the reader's interest. This hook serves as a way to make your introduction more engaging and compelling. For example, if you are writing a research paper on the impact of climate change on biodiversity, you could start your introduction with a statistic about the number of species that have gone extinct due to climate change. This will immediately grab the reader's attention and make them realize the urgency and importance of the topic.

Introducing Your Topic

Provide a brief overview, which should give the reader a general understanding of the subject matter and its significance. Explain the importance of the topic and its relevance to the field. This will help the reader understand why your research is significant and why they should continue reading. Continuing with the example of climate change and biodiversity, you could explain how climate change is one of the greatest threats to global biodiversity, how it affects ecosystems, and the potential consequences for both wildlife and human populations. By providing this context, you are setting the stage for the rest of your research paper and helping the reader understand the importance of your study.

Presenting Your Thesis Statement

The thesis statement should directly address your research question and provide a preview of the main arguments or findings discussed in your paper. Make sure your thesis statement is clear, concise, and well-supported by the evidence you will present in your research paper. By presenting a strong and focused thesis statement, you are providing the reader with the information they could anticipate in your research paper. This will help them understand the purpose and scope of your study and will make them more inclined to continue reading.

Writing Techniques for an Effective Introduction

When crafting an introduction, it is crucial to pay attention to the finer details that can elevate your writing to the next level. By utilizing specific writing techniques, you can captivate your readers and draw them into your research journey.

Using Clear and Concise Language

One of the most important writing techniques to employ in your introduction is the use of clear and concise language. By choosing your words carefully, you can effectively convey your ideas to the reader. It is essential to avoid using jargon or complex terminology that may confuse or alienate your audience. Instead, focus on communicating your research in a straightforward manner to ensure that your introduction is accessible to both experts in your field and those who may be new to the topic. This approach allows you to engage a broader audience and make your research more inclusive.

Establishing the Relevance of Your Research

One way to establish the relevance of your research is by highlighting how it fills a gap in the existing literature. Explain how your study addresses a significant research question that has not been adequately explored. By doing this, you demonstrate that your research is not only unique but also contributes to the broader knowledge in your field. Furthermore, it is important to emphasize the potential impact of your research. Whether it is advancing scientific understanding, informing policy decisions, or improving practical applications, make it clear to the reader how your study can make a difference.

By employing these two writing techniques in your introduction, you can effectively engage your readers. Take your time to craft an introduction that is both informative and captivating, leaving your readers eager to delve deeper into your research.

Revising and Polishing Your Introduction

Once you have written your introduction, it is crucial to revise and polish it to ensure that it effectively sets the stage for your research paper.

Self-Editing Techniques

Review your introduction for clarity, coherence, and logical flow. Ensure each paragraph introduces a new idea or argument with smooth transitions.

Check for grammatical errors, spelling mistakes, and awkward sentence structures.

Ensure that your introduction aligns with the overall tone and style of your research paper.

Seeking Feedback for Improvement

Consider seeking feedback from peers, colleagues, or your instructor. They can provide valuable insights and suggestions for improving your introduction. Be open to constructive criticism and use it to refine your introduction and make it more compelling for the reader.

Writing an introduction for a research paper requires careful thought and planning. By understanding the purpose of the introduction, preparing adequately, structuring effectively, and employing writing techniques, you can create an engaging and informative introduction for your research. Remember to revise and polish your introduction to ensure that it accurately represents the main ideas and arguments in your research paper. With a well-crafted introduction, you will capture the reader's attention and keep them inclined to your paper.

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Crafting the Perfect Example of Introduction in a Research Paper

Crafting the perfect introduction for a research paper is both an art and a science. The introduction sets the stage for your entire study, providing essential context, presenting the research problem, and outlining the structure of your paper. Done well, it captures the reader's interest and guides them seamlessly into the body of your research. This article explores the key elements and strategies for writing an effective introduction, common pitfalls to avoid, and examples of successful introductions to help you master this crucial component of your research paper.

Key Takeaways

• A well-crafted introduction establishes context, presents the research problem, and outlines the structure of the paper.
• Capturing the reader's interest and summarizing existing research are essential for an effective introduction.
• Using a funnel approach and engaging hooks can make your introduction more compelling.
• Avoid common pitfalls such as overloading with information and lacking a clear thesis statement.
• Analyzing examples of successful introductions can provide valuable insights and guidance.

Understanding the Purpose of an Introduction in a Research Paper

The introduction for a research paper is where you set up your topic and approach for the reader. It has several key goals:

Establishing Context and Importance

In the initial part of your introduction, you need to establish the context and importance of your research. This involves providing necessary background information and setting the stage for your study. A good introduction prepares readers to care about and understand your research by presenting the broader context and highlighting why the topic is significant.

Presenting the Research Problem

Next, you should clearly present the research problem or question that your paper addresses. This is crucial as it defines the focus of your study and guides the reader on what to expect. A well-defined research problem helps in justifying the need for your study and sets the direction for your research.

Outlining the Structure of the Paper

Finally, outline the structure of your paper. This provides a roadmap for the reader, helping them understand how your argument will unfold. By briefly describing the main sections of your paper, you make it easier for readers to follow your line of reasoning and see how each part contributes to your overall thesis.

Key Elements of an Effective Research Paper Introduction

An effective research paper introduction serves as a crucial roadmap for your readers . It sets the stage for your research by presenting the topic, capturing interest, summarizing existing research, and highlighting the study's contributions. Each element plays a vital role in ensuring that your introduction is both engaging and informative.

Strategies for Writing a Compelling Introduction

When crafting an introduction for your research paper, employing effective strategies is crucial to engage your readers and set the stage for your study. Here are some key strategies to consider:

Using a Funnel Approach

Start broad and gradually narrow down to your specific research problem. This method helps in establishing context and importance for your study. By beginning with a general overview and then focusing on your specific research question, you guide your readers smoothly into the core of your paper.

Incorporating Engaging Hooks

To capture your reader's interest, consider opening with a compelling story, a strong quotation, or a thought-provoking question. Avoid the "Dictionary" Introduction , as it tends to be dry and unengaging. Instead, choose one strategy to avoid giving an impression that your paper is more flash than substance.

Maintaining Clarity and Conciseness

A concise, engaging, and well-written introduction will start your readers off thinking highly of your analytical skills, your writing style, and your research approach. Avoid overloading your introduction with too much information. Focus on being clear and to the point, ensuring that your readers understand the significance of your research without feeling overwhelmed.

Common Pitfalls to Avoid in Research Paper Introductions

When crafting the introduction of your research paper, it is crucial to avoid several common pitfalls that can undermine the effectiveness of your work. Avoiding these mistakes will help you create a more compelling and coherent introduction.

Overloading with Information

While the literature review is crucial, it should not overwhelm your introduction. Keep it concise and focused on setting the foundation for your manuscript. Overloading your introduction with too much information can confuse the reader and dilute the main points you want to convey.

Lack of Clear Thesis Statement

A clear thesis statement is essential for guiding the reader through your research. Without it, your introduction may lack direction and purpose. Ensure that your thesis statement is prominently positioned and clearly articulated to provide a roadmap for your paper.

Ignoring the Research Gap

One of the primary purposes of the introduction is to highlight the research gap your study aims to fill. Ignoring this aspect can make your research seem redundant or unoriginal. Make sure to clearly identify and articulate the gap in the existing literature that your research addresses.

Examples of Well-Written Research Paper Introductions

When examining well-written research paper introductions, it is essential to focus on several key aspects that contribute to their effectiveness. By analyzing successful introductions, comparing different approaches, and learning from common mistakes, you can gain valuable insights into crafting your own compelling introduction.

Analyzing Successful Introductions

A successful introduction often begins with a broad overview of the topic before narrowing down to the specific research question. This funnel structure ensures that the reader is gradually led into the core of the research. Additionally, a well-crafted introduction will clearly state the research problem and its significance, providing a strong foundation for the rest of the paper.

Comparing Different Approaches

Different research papers may adopt various strategies in their introductions. Some may start with an engaging hook, such as an interesting fact or a surprising statistic, to capture the reader's attention. Others might begin with a review of existing literature to establish the context and highlight the research gap. By comparing these approaches, you can determine which method best suits your research topic and audience.

Learning from Common Mistakes

One common mistake in research paper introductions is overloading the reader with too much information. It is crucial to be concise and focused, ensuring that every sentence serves a purpose. Another pitfall is failing to clearly state the thesis or research question, leaving the reader uncertain about the paper's direction. By avoiding these errors, you can create a more effective and engaging introduction.

The Role of Background Information in an Introduction

Providing background information in the introduction of a research paper is crucial for setting the stage for your study. This initial part of the introduction prepares the readers for more detailed and specific information that is given later. It establishes the scope, context, and significance of the research problem you are addressing. By offering a brief history of the topic and summarizing previous research, you help readers understand the foundation upon which your study is built.

The Importance of a Strong Thesis Statement

A strong thesis statement is the backbone of any well-crafted research paper. It serves as the guiding light for both the writer and the reader, ensuring that the paper remains focused and coherent. A clear and assertive thesis statement not only presents the main argument but also sets the tone for the entire paper. This is crucial in academic writing, where the thesis statement marks the conclusive part of the introduction and transitions to the actual research.

Defining the Thesis Statement

The thesis statement is a concise summary of the main point or claim of the paper. It should be specific, supported by evidence, and engaging enough to capture the reader's interest. Crafting a strong thesis statement can help alleviate thesis anxiety by providing a clear direction for your research and writing process.

Positioning the Thesis within the Introduction

The placement of the thesis statement is critical. It typically appears at the end of the introduction, serving as a bridge between the background information and the main body of the paper. This strategic positioning helps in establishing the context and importance of the research problem, making it easier for readers to follow the subsequent arguments.

Ensuring Consistency Throughout the Paper

A well-defined thesis statement ensures consistency throughout the paper. Every section and paragraph should relate back to the thesis, reinforcing the main argument. This coherence not only strengthens the paper's overall structure but also enhances its persuasiveness. Discussing your thesis with others can provide valuable feedback and help refine your argument, ensuring it remains clear and compelling.

A strong thesis statement is the backbone of any successful academic paper. It provides clarity and direction, helping you stay focused and organized throughout your writing process. If you're struggling with sleepless nights, anxiety, and feeling overwhelmed, our step-by-step Thesis Action Plan is here to help. Visit our website to claim your special offer now and transform your thesis writing experience!

Crafting the perfect introduction for a research paper is a nuanced and essential task that sets the stage for the entire study. This article has explored the critical components that make up an effective introduction, including presenting the research topic, capturing reader interest, summarizing existing research, positioning the author's approach, defining the specific research problem, highlighting the novelty and contributions of the study, and providing an overview of the paper's structure. By adhering to these guidelines, researchers can ensure that their introductions are not only engaging but also provide a clear and concise roadmap for their readers. Ultimately, a well-crafted introduction paves the way for a compelling and impactful research paper, guiding the reader through the complexities of the study with clarity and precision.

Frequently Asked Questions

What is the purpose of an introduction in a research paper.

The purpose of an introduction in a research paper is to set the context for the research, present the research problem, and outline the structure of the paper. It helps readers understand the importance of the study and what to expect from the paper.

How can I capture the reader's interest in the introduction?

To capture the reader's interest, you can use engaging hooks such as interesting facts, quotes, or questions. Additionally, clearly stating the significance of the research and its potential impact can also draw readers in.

What are common pitfalls to avoid in research paper introductions?

Common pitfalls include overloading the introduction with too much information, failing to present a clear thesis statement, and ignoring the research gap. It's important to be concise and focused.

Why is a strong thesis statement important in an introduction?

A strong thesis statement is crucial because it clearly defines the main argument or focus of the research paper. It guides the direction of the paper and ensures consistency throughout the writing.

What strategies can I use to write a compelling introduction?

Some strategies include using a funnel approach to gradually narrow down the topic, incorporating engaging hooks to capture interest, and maintaining clarity and conciseness to ensure the introduction is easy to follow.

How can I provide background information effectively in the introduction?

To provide background information effectively, you should offer historical context, review relevant literature, and set up the research question. This helps to establish the foundation for your study and shows how it fits into the existing body of research.

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Starting Your Research Paper: Writing an Introductory Paragraph

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The Dreaded Introductory Paragraph

Writing the introductory paragraph can be a frustrating and slow process -- but it doesn't have to be.  If you planned your paper out, then most of the introductory paragraph is already written.  Now you just need a beginning and an end.

Here's an introductory paragraph for a paper I wrote.  I started the paper with a factoid, then presented each main point of my paper and then ended with my thesis statement.

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What is a "good" introduction?

Citing sources in the introduction, "introduction checklist" from: how to write a good scientific paper. chris a. mack. spie. 2018..

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This is where you describe briefly and clearly why you are writing the paper. The introduction supplies sufficient background information for the reader to understand and evaluate the experiment you did. It also supplies a rationale for the study.

• Present the problem and the proposed solution
• Presents nature and scope of the problem investigated
• Reviews the pertinent literature to orient the reader
• States the method of the experiment
• State the principle results of the experiment

It is important to cite sources in the introduction section of your paper as evidence of the claims you are making. There are ways of citing sources in the text so that the reader can find the full reference in the literature cited section at the end of the paper, yet the flow of the reading is not badly interrupted. Below are some example of how this can be done:     "Smith (1983) found that N-fixing plants could be infected by several different species of Rhizobium."     "Walnut trees are known to be allelopathic (Smith 1949,  Bond et al. 1955, Jones and Green 1963)."     "Although the presence of Rhizobium normally increases the growth of legumes (Nguyen 1987), the opposite effect has been observed (Washington 1999)." Note that articles by one or two authors are always cited in the text using their last names. However, if there are more than two authors, the last name of the 1st author is given followed by the abbreviation et al. which is Latin for "and others". 

From:  https://writingcenter.gmu.edu/guides/imrad-reports-introductions

• Indicate the field of the work, why this field is important, and what has already been done (with proper citations).
• Indicate a gap, raise a research question, or challenge prior work in this territory.
• Outline the purpose and announce the present research, clearly indicating what is novel and why it is significant.
• Avoid: repeating the abstract; providing unnecessary background information; exaggerating the importance of the work; claiming novelty without a proper literature search. 
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How to Write a Research Introduction

Last Updated: December 6, 2023 Fact Checked

This article was co-authored by Megan Morgan, PhD . Megan Morgan is a Graduate Program Academic Advisor in the School of Public & International Affairs at the University of Georgia. She earned her PhD in English from the University of Georgia in 2015. There are 7 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 2,654,743 times.

The introduction to a research paper can be the most challenging part of the paper to write. The length of the introduction will vary depending on the type of research paper you are writing. An introduction should announce your topic, provide context and a rationale for your work, before stating your research questions and hypothesis. Well-written introductions set the tone for the paper, catch the reader's interest, and communicate the hypothesis or thesis statement.

Introducing the Topic of the Paper

• In scientific papers this is sometimes known as an "inverted triangle", where you start with the broadest material at the start, before zooming in on the specifics. [2] X Research source
• The sentence "Throughout the 20th century, our views of life on other planets have drastically changed" introduces a topic, but does so in broad terms.
• It provides the reader with an indication of the content of the essay and encourages them to read on.

• For example, if you were writing a paper about the behaviour of mice when exposed to a particular substance, you would include the word "mice", and the scientific name of the relevant compound in the first sentences.
• If you were writing a history paper about the impact of the First World War on gender relations in Britain, you should mention those key words in your first few lines.

• This is especially important if you are attempting to develop a new conceptualization that uses language and terminology your readers may be unfamiliar with.

• If you use an anecdote ensure that is short and highly relevant for your research. It has to function in the same way as an alternative opening, namely to announce the topic of your research paper to your reader.
• For example, if you were writing a sociology paper about re-offending rates among young offenders, you could include a brief story of one person whose story reflects and introduces your topic.
• This kind of approach is generally not appropriate for the introduction to a natural or physical sciences research paper where the writing conventions are different.

Establishing the Context for Your Paper

• It is important to be concise in the introduction, so provide an overview on recent developments in the primary research rather than a lengthy discussion.
• You can follow the "inverted triangle" principle to focus in from the broader themes to those to which you are making a direct contribution with your paper.
• A strong literature review presents important background information to your own research and indicates the importance of the field.

• By making clear reference to existing work you can demonstrate explicitly the specific contribution you are making to move the field forward.
• You can identify a gap in the existing scholarship and explain how you are addressing it and moving understanding forward.

• For example, if you are writing a scientific paper you could stress the merits of the experimental approach or models you have used.
• Stress what is novel in your research and the significance of your new approach, but don't give too much detail in the introduction.
• A stated rationale could be something like: "the study evaluates the previously unknown anti-inflammatory effects of a topical compound in order to evaluate its potential clinical uses".

Specifying Your Research Questions and Hypothesis

• The research question or questions generally come towards the end of the introduction, and should be concise and closely focused.
• The research question might recall some of the key words established in the first few sentences and the title of your paper.
• An example of a research question could be "what were the consequences of the North American Free Trade Agreement on the Mexican export economy?"
• This could be honed further to be specific by referring to a particular element of the Free Trade Agreement and the impact on a particular industry in Mexico, such as clothing manufacture.
• A good research question should shape a problem into a testable hypothesis.

• If possible try to avoid using the word "hypothesis" and rather make this implicit in your writing. This can make your writing appear less formulaic.
• In a scientific paper, giving a clear one-sentence overview of your results and their relation to your hypothesis makes the information clear and accessible. [10] X Trustworthy Source PubMed Central Journal archive from the U.S. National Institutes of Health Go to source
• An example of a hypothesis could be "mice deprived of food for the duration of the study were expected to become more lethargic than those fed normally".

• This is not always necessary and you should pay attention to the writing conventions in your discipline.
• In a natural sciences paper, for example, there is a fairly rigid structure which you will be following.
• A humanities or social science paper will most likely present more opportunities to deviate in how you structure your paper.

Research Introduction Help

Community Q&A

• Use your research papers' outline to help you decide what information to include when writing an introduction. Thanks Helpful 0 Not Helpful 1
• Consider drafting your introduction after you have already completed the rest of your research paper. Writing introductions last can help ensure that you don't leave out any major points. Thanks Helpful 0 Not Helpful 0

• Avoid emotional or sensational introductions; these can create distrust in the reader. Thanks Helpful 50 Not Helpful 12
• Generally avoid using personal pronouns in your introduction, such as "I," "me," "we," "us," "my," "mine," or "our." Thanks Helpful 31 Not Helpful 7
• Don't overwhelm the reader with an over-abundance of information. Keep the introduction as concise as possible by saving specific details for the body of your paper. Thanks Helpful 24 Not Helpful 14

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• ↑ https://library.sacredheart.edu/c.php?g=29803&p=185916
• ↑ https://www.aresearchguide.com/inverted-pyramid-structure-in-writing.html
• ↑ https://libguides.usc.edu/writingguide/introduction
• ↑ https://writing.wisc.edu/Handbook/PlanResearchPaper.html
• ↑ https://dept.writing.wisc.edu/wac/writing-an-introduction-for-a-scientific-paper/
• ↑ https://writing.wisc.edu/handbook/assignments/planresearchpaper/
• ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3178846/

About This Article

To introduce your research paper, use the first 1-2 sentences to describe your general topic, such as “women in World War I.” Include and define keywords, such as “gender relations,” to show your reader where you’re going. Mention previous research into the topic with a phrase like, “Others have studied…”, then transition into what your contribution will be and why it’s necessary. Finally, state the questions that your paper will address and propose your “answer” to them as your thesis statement. For more information from our English Ph.D. co-author about how to craft a strong hypothesis and thesis, keep reading! Did this summary help you? Yes No

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How to Write an Introduction for a Psychology Paper

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Emily is a board-certified science editor who has worked with top digital publishing brands like Voices for Biodiversity, Study.com, GoodTherapy, Vox, and Verywell.

• Writing Tips

If you are writing a psychology paper, it is essential to kick things off with a strong introduction. The introduction to a psychology research paper helps your readers understand why the topic is important and what they need to know before they delve deeper.

Your goal in this section is to introduce the topic to the reader, provide an overview of previous research on the topic, and identify your own hypothesis .

At a Glance

Writing a great introduction can be a great foundation for the rest of your psychology paper. To create a strong intro:

• Research your topic
• Outline your paper
• Introduce your topic
• Summarize the previous research
• Present your hypothesis or main argument

Before You Write an Introduction

There are some important steps you need to take before you even begin writing your introduction. To know what to write, you need to collect important background information and create a detailed plan.

Research Your Topic

Search a journal database, PsychInfo or ERIC, to find articles on your subject. Once you have located an article, look at the reference section to locate other studies cited in the article. As you take notes from these articles, be sure to write down where you found the information.

A simple note detailing the author's name, journal, and date of publication can help you keep track of sources and avoid plagiarism.

Create a Detailed Outline

This is often one of the most boring and onerous steps, so students tend to skip outlining and go straight to writing. Creating an outline might seem tedious, but it can be an enormous time-saver down the road and will make the writing process much easier.

Start by looking over the notes you made during the research process and consider how you want to present all of your ideas and research.

Introduce the Topic

Once you are ready to write your introduction, your first task is to provide a brief description of the research question. What is the experiment or study attempting to demonstrate? What phenomena are you studying? Provide a brief history of your topic and explain how it relates to your current research.

As you are introducing your topic, consider what makes it important. Why should it matter to your reader? The goal of your introduction is not only to let your reader know what your paper is about, but also to justify why it is important for them to learn more.

If your paper tackles a controversial subject and is focused on resolving the issue, it is important to summarize both sides of the controversy in a fair and impartial way. Consider how your paper fits in with the relevant research on the topic.

The introduction of a research paper is designed to grab interest. It should present a compelling look at the research that already exists and explain to readers what questions your own paper will address.

Summarize Previous Research

The second task of your introduction is to provide a well-rounded summary of previous research that is relevant to your topic. So, before you begin to write this summary, it is important to research your topic thoroughly.

Finding appropriate sources amid thousands of journal articles can be a daunting task, but there are several steps you can take to simplify your research. If you have completed the initial steps of researching and keeping detailed notes, writing your introduction will be much easier.

It is essential to give the reader a good overview of the historical context of the issue you are writing about, but do not feel like you must provide an exhaustive review of the subject. Focus on hitting the main points, and try to include the most relevant studies.

You might describe previous research findings and then explain how the current study differs or expands upon earlier research.

Provide Your Hypothesis

Once you have summarized the previous research, explain areas where the research is lacking or potentially flawed. What is missing from previous studies on your topic? What research questions have yet to be answered? Your hypothesis should lead to these questions.

At the end of your introduction, offer your hypothesis and describe what you expected to find in your experiment or study.

The introduction should be relatively brief. You want to give your readers an overview of a topic, explain why you are addressing it, and provide your arguments.

Tips for Writing Your Psychology Paper Intro

• Use 3x5 inch note cards to write down notes and sources.
• Look in professional psychology journals for examples of introductions.
• Remember to cite your sources.
• Maintain a working bibliography with all of the sources you might use in your final paper. This will make it much easier to prepare your reference section later on.
• Use a copy of the APA style manual to ensure that your introduction and references are in proper APA format .

What This Means For You

Before you delve into the main body of your paper, you need to give your readers some background and present your main argument in the introduction of you paper. You can do this by first explaining what your topic is about, summarizing past research, and then providing your thesis.

Armağan A. How to write an introduction section of a scientific article ?  Turk J Urol . 2013;39(Suppl 1):8-9. doi:10.5152/tud.2013.046

Fried T, Foltz C, Lendner M, Vaccaro AR. How to write an effective introduction .  Clin Spine Surg . 2019;32(3):111-112. doi:10.1097/BSD.0000000000000714

Jawaid SA, Jawaid M. How to write introduction and discussion .  Saudi J Anaesth . 2019;13(Suppl 1):S18-S19. doi:10.4103/sja.SJA_584_18

American Psychological Association. Information Recommended for Inclusion in Manuscripts That Report New Data Collections Regardless of Research Design . Published 2020.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

6 Examples of Research Paper Introductions to Hook Your Readers

Welcome to our guide on research paper introductions!

As you may already know, the introduction is a critical component of any research paper, as it sets the tone for the rest of the paper and establishes the reader’s expectations.

The introductory paragraph in a research paper should give an overview of what the reader can expect from the rest of the paper.

It should also establish a context for readers who are new to this topic. More importantly, when writing a research paper introduction, it’s best to focus on two key points: the problem being addressed and how this particular study (or studies) addresses it.

If those two points are clear then readers should be able to follow along as they read more into your paper.

In the following sections, we’ll provide you with examples of different types of research paper introductions to help you get started.

Types of Research Paper Introductions

General introductions.

A general introduction is suitable when you’re discussing a range of different topics or subjects within one paper. It provides the reader with an idea of where you stand in regard to the topic at hand and can be followed up with a sentence or two explaining your specific angle.

Topic: The Effect of Social Media on Mental Health

Social media has become an integral part of our daily lives, and its impact on mental health has become a subject of increasing concern in recent years. While social media platforms have provided a new means of communication and access to information, they have also been linked to negative mental health outcomes such as depression, anxiety, and low self-esteem. This research paper aims to explore the relationship between social media use and mental health outcomes. Specifically, we will investigate how social media affects individuals’ perceptions of themselves and their social relationships, as well as the potential impact on their emotional well-being. Through a thorough literature review and original research, we hope to shed light on the complex relationship between social media and mental health and provide insights into effective interventions for those who may be negatively impacted by social media use.

Topic: Formal Presentations at University

Most universities require their graduate-level courses to have some form of formal presentation such as a dissertation, master’s thesis, or doctoral dissertation. These presentations often take the form of an oral defense. Formal presentations provide both teachers and students with feedback in order to make future projects better. Teachers also use these projects to gauge student performance and provide guidance during group discussions throughout the course. What makes these oral defenses different than others is that they must adhere to strict guidelines set forth by the institution overseeing them. Failure to comply with these guidelines may result in expulsion from the university. Oral defenses typically contain three major parts: an opening statement, main body, and closing statement. However, some institutions may offer variations of this format. For instance, many institutions now require a written version of the presentation that includes all major aspects required by the institution.

Quote-Based Research Paper Introduction

This type of introduction is ideal for research papers that rely heavily on quotes to establish their point.

In these cases, quoting the most relevant piece of information is usually necessary because doing so will allow the reader to better understand what your discussion entails.

With that said, remember that every quote you include needs to add something significant and/or novel which hasn’t been covered before – otherwise it won’t be worth including in your paper!

Topic: International Student Success at the University Level

Shakespeare once said that “A rose by any other name would smell as sweet.” This line from Romeo and Juliet suggests that names don’t matter. Similarly, the fact that someone goes to school in a certain country does not affect the quality of education. Yet research has shown that international students perform worse academically than domestic ones in American colleges and universities. So, the question becomes: How do we foster success among international students? It is possible that differences in culture and socialization contribute to the observed gaps in academic achievement. Given that, our next step should be to examine the challenges faced by international students in an effort to find effective ways of addressing these challenges.

Topic: The Impact of Social Media on Mental Health

As Mark Twain once said, “Comparison is the death of joy.” In today’s world, social media platforms provide us with countless opportunities to compare our lives to those of others, often leading to feelings of inadequacy, anxiety, and depression. Research has shown that excessive social media use can have a negative impact on mental health, particularly among young adults. Given the increasing prevalence of social media in our daily lives, it’s important to explore this topic in more depth and understand the ways in which social media use can impact mental health outcomes.

Surprising Fact-based Introductions

A surprising fact-based introduction works well with scientific or medical topics where there is surprising new evidence that directly impacts how people view a certain issue. In such cases, it’s often necessary to give some background on what exactly is at stake in order to highlight why it’s important and relevant. Following that, you can introduce the key findings and what they mean.

Topic: The relationship between caffeine and weight loss

Caffeine is a well-known stimulant, which is consumed by millions of people on a daily basis in the form of coffee, tea, energy drinks, or pills. Although it’s unclear how much caffeine is too much for an individual to consume each day, it’s commonly believed that the positive effects of caffeine are canceled out by the increased appetite that results from drinking caffeinated beverages. But did you know that caffeine might actually help you lose weight?! Recent research conducted by a team of investigators from the Johns Hopkins Bloomberg School of Public Health and Harvard T.H. Chan School of Public Health found that the more caffeine an individual consumes, the lower their risk for obesity. That’s right: while it may sound counterintuitive, having one or two cups of coffee per day could actually decrease your chances of becoming overweight or obese.

Topic: The Benefits of Napping on Memory Retention

Did you know that a short nap can help boost your memory retention by up to 30%? Most people think of napping as something reserved for children or lazy adults, but recent research has shown that a short nap can actually be beneficial for cognitive function, particularly in regard to memory. In today’s fast-paced world, we often prioritize productivity over rest, but the science behind napping suggests that we should be doing the opposite. In this paper, we will explore the benefits of napping on memory retention and discuss how individuals and organizations can incorporate napping into their daily routines for optimal cognitive performance.

Explanatory research paper introductions

These types of research paper introductions are used when you’re introducing a new concept or idea that requires the audience to have knowledge of basic facts in order to follow along.

In this case, it’s critical that you provide the necessary background information and then follow up with a statement about why the rest of the research is interesting and/or relevant.

For example, you might say that the paper discusses a recent study on mindfulness and meditation.

In order to fully grasp the research and the claims being made, it’s necessary to first understand what mindfulness is and why it’s relevant. The following paragraphs would therefore serve as an introduction to both topics.

Topic: Mindfulness

Mindfulness is a mental state achieved by focusing one’s awareness on the present moment, while calmly acknowledging and accepting one’s feelings, thoughts, and bodily sensations. Regular practice of mindfulness can be highly beneficial to both mental and physical health. There are many different techniques for practicing mindfulness: Mindful walking, sitting with an open mind, eating without distractions, listening deeply to others, or simply noticing what you see in your environment. What’s most important is that you develop the ability to pay attention in a way that helps you connect with yourself and the world around you. And just like anything else, mindfulness takes practice. The best way to get started is by taking part in a course or program offered at your local community center, hospital, or online.

Topic: The Effectiveness of Online Learning in Higher Education

As more and more students turn to online learning to pursue their higher education, questions have arisen regarding the effectiveness of this type of education. While online learning offers a number of benefits, such as flexibility and convenience, it also presents unique challenges, including the lack of face-to-face interaction with instructors and classmates. This research paper aims to examine the effectiveness of online learning in higher education and compare it to traditional classroom-based learning. By conducting a literature review and analyzing data from surveys and interviews with students and instructors, this paper seeks to identify the advantages and disadvantages of online learning and provide recommendations for improving its effectiveness.

Narration-based paper introductions

This type of research paper introduction is used when you’re discussing a topic or event in detail.

You could talk about why it’s important, explain what happened and how it relates to your larger point, summarize what happened (as with a timeline), or present an example to prove your thesis.

Whatever you choose, it’s imperative that you make your readers want to keep reading.

This is done by telling a compelling story, using storytelling elements such as tension and conflict, or painting a vivid picture of the scene with sensory details.

Topic: The impact of stress on memory and learning

It’s well known that stress can impair our ability to learn new things, but it also has an impact on our memories. Well, I have first-hand experience with this. The night before my midterm, I had a major fight with my partner. This was one of the worst arguments we’ve ever had and it went on for hours. Needless to say, it stressed me out and there’s no doubt that it hurt my performance on the test. The funny thing is that in the days following the argument, my partner and I were able to clear everything up, so now we’re good again. But this experience taught me one very important lesson: the impact of stress on memory and learning might seem negligible but it can actually have a long-term impact on academic performance.

Topic: The Effects of Social Media on Mental Health

As I sit here scrolling through my Instagram feed, I can’t help but feel a sense of envy and inadequacy wash over me. The seemingly perfect lives of influencers and friends alike are on full display, leaving me to question why I don’t have the same level of success and happiness. It’s no secret that social media has become a ubiquitous part of our daily lives, with billions of people using platforms like Instagram, Facebook, and Twitter to connect with others and share their lives. But what are the effects of this constant exposure to other people’s carefully curated images and narratives? Are we putting ourselves at risk for developing mental health issues like anxiety and depression? In this paper, I will explore the research that has been done on the topic of social media and mental health, examining both the positive and negative effects that social media can have on our psychological well-being. By the end of this paper, you will have a better understanding of how social media impacts mental health and what steps we can take to mitigate its negative effects.

Teaser-based research paper introductions

The most common types of research paper introductions are teasers.

This simply means that your first sentence is a hook: something to grab your reader’s attention and make them want to read more.

One way to create a compelling teaser is by addressing an interesting question or controversial topic, such as “Why do some people succeed and others fail?”

Another approach is to pose a problem that you plan to solve.

Here are examples of a teaser-based research paper introductions.

Topic: Why do some people succeed and others fail?

Failure is a part of life. We all fail at one time or another, it’s just something that happens. But why do some people fail more than others? And what about people who never seem to fail? You see them every day, they are in your office and everywhere else you go. These people always seem to be successful and highly driven. How do they do it? This is a question that has puzzled psychologists and other social scientists for years. In the past, a lot of psychologists believed that success was due to differences in abilities and intelligence. Others said it depended on luck. Still, others believed that family background determined whether someone succeeded or not. As you can imagine, these explanations led to considerable debate and disagreement among scholars.

Topic: The Future of Artificial Intelligence in Healthcare

Are we on the cusp of a revolution in healthcare? With the rise of artificial intelligence (AI), the answer might just be yes. From machine learning algorithms that can identify diseases faster and more accurately than humans to chatbots that can answer patient questions 24/7, AI is poised to transform every aspect of healthcare. But as with any technology, there are risks and challenges that must be addressed. In this paper, we’ll explore the ways in which AI is being used in healthcare today and the potential implications for patients, doctors, and the healthcare industry as a whole. Buckle up, because the future is here, and it’s powered by AI.

Final Remarks: Research Paper Introductions

Crafting an effective research paper introduction can be challenging, but with the right approach and attention to detail, you can create an introduction that captures the reader’s attention and sets the stage for the rest of the paper.

Whether you choose a general introduction, a quote-based introduction, a surprising fact-based introduction, or an anecdotal introduction, be sure to clearly state your topic and thesis, provide background information, and engage your readers in meaning.

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Microsoft 365 Life Hacks > Writing > How to write an introduction for a research paper

How to write an introduction for a research paper

Beginnings are hard. Beginning a research paper is no exception. Many students—and pros—struggle with how to write an introduction for a research paper.

This short guide will describe the purpose of a research paper introduction and how to create a good one.

What is an introduction for a research paper?

Introductions to research papers do a lot of work.

It may seem obvious, but introductions are always placed at the beginning of a paper. They guide your reader from a general subject area to the narrow topic that your paper covers. They also explain your paper’s:

• Scope: The topic you’ll be covering
• Context: The background of your topic
• Importance: Why your research matters in the context of an industry or the world

Your introduction will cover a lot of ground. However, it will only be half of a page to a few pages long. The length depends on the size of your paper as a whole. In many cases, the introduction will be shorter than all of the other sections of your paper.

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Why is an introduction vital to a research paper?

The introduction to your research paper isn’t just important. It’s critical.

Your readers don’t know what your research paper is about from the title. That’s where your introduction comes in. A good introduction will:

• Help your reader understand your topic’s background
• Explain why your research paper is worth reading
• Offer a guide for navigating the rest of the piece
• Pique your reader’s interest

Without a clear introduction, your readers will struggle. They may feel confused when they start reading your paper. They might even give up entirely. Your introduction will ground them and prepare them for the in-depth research to come.

What should you include in an introduction for a research paper?

Research paper introductions are always unique. After all, research is original by definition. However, they often contain six essential items. These are:

• An overview of the topic. Start with a general overview of your topic. Narrow the overview until you address your paper’s specific subject. Then, mention questions or concerns you had about the case. Note that you will address them in the publication.
• Prior research. Your introduction is the place to review other conclusions on your topic. Include both older scholars and modern scholars. This background information shows that you are aware of prior research. It also introduces past findings to those who might not have that expertise.
• A rationale for your paper. Explain why your topic needs to be addressed right now. If applicable, connect it to current issues. Additionally, you can show a problem with former theories or reveal a gap in current research. No matter how you do it, a good rationale will interest your readers and demonstrate why they must read the rest of your paper.
• Describe the methodology you used. Recount your processes to make your paper more credible. Lay out your goal and the questions you will address. Reveal how you conducted research and describe how you measured results. Moreover, explain why you made key choices.
• A thesis statement. Your main introduction should end with a thesis statement. This statement summarizes the ideas that will run through your entire research article. It should be straightforward and clear.
• An outline. Introductions often conclude with an outline. Your layout should quickly review what you intend to cover in the following sections. Think of it as a roadmap, guiding your reader to the end of your paper.

These six items are emphasized more or less, depending on your field. For example, a physics research paper might emphasize methodology. An English journal article might highlight the overview.

Three tips for writing your introduction

We don’t just want you to learn how to write an introduction for a research paper. We want you to learn how to make it shine.

There are three things you can do that will make it easier to write a great introduction. You can:

• Write your introduction last. An introduction summarizes all of the things you’ve learned from your research. While it can feel good to get your preface done quickly, you should write the rest of your paper first. Then, you’ll find it easy to create a clear overview.
• Include a strong quotation or story upfront. You want your paper to be full of substance. But that doesn’t mean it should feel boring or flat. Add a relevant quotation or surprising anecdote to the beginning of your introduction. This technique will pique the interest of your reader and leave them wanting more.
• Be concise. Research papers cover complex topics. To help your readers, try to write as clearly as possible. Use concise sentences. Check for confusing grammar or syntax . Read your introduction out loud to catch awkward phrases. Before you finish your paper, be sure to proofread, too. Mistakes can seem unprofessional.

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How to Create a Structured Research Paper Outline | Example

Published on August 7, 2022 by Courtney Gahan . Revised on August 15, 2023.

A research paper outline is a useful tool to aid in the writing process , providing a structure to follow with all information to be included in the paper clearly organized.

A quality outline can make writing your research paper more efficient by helping to:

• Organize your thoughts
• Understand the flow of information and how ideas are related
• Ensure nothing is forgotten

A research paper outline can also give your teacher an early idea of the final product.

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Table of contents

Research paper outline example, how to write a research paper outline, formatting your research paper outline, language in research paper outlines.

• Definition of measles
• Rise in cases in recent years in places the disease was previously eliminated or had very low rates of infection
• Figures: Number of cases per year on average, number in recent years. Relate to immunization
• Symptoms and timeframes of disease
• Risk of fatality, including statistics
• How measles is spread
• Immunization procedures in different regions
• Different regions, focusing on the arguments from those against immunization
• Immunization figures in affected regions
• High number of cases in non-immunizing regions
• Illnesses that can result from measles virus
• Fatal cases of other illnesses after patient contracted measles
• Summary of arguments of different groups
• Summary of figures and relationship with recent immunization debate
• Which side of the argument appears to be correct?

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Follow these steps to start your research paper outline:

• Decide on the subject of the paper
• Write down all the ideas you want to include or discuss
• Organize related ideas into sub-groups
• Arrange your ideas into a hierarchy: What should the reader learn first? What is most important? Which idea will help end your paper most effectively?
• Create headings and subheadings that are effective
• Format the outline in either alphanumeric, full-sentence or decimal format

There are three different kinds of research paper outline: alphanumeric, full-sentence and decimal outlines. The differences relate to formatting and style of writing.

• Alphanumeric
• Full-sentence

An alphanumeric outline is most commonly used. It uses Roman numerals, capitalized letters, arabic numerals, lowercase letters to organize the flow of information. Text is written with short notes rather than full sentences.

• Sub-point of sub-point 1

Essentially the same as the alphanumeric outline, but with the text written in full sentences rather than short points.

• Additional sub-point to conclude discussion of point of evidence introduced in point A

A decimal outline is similar in format to the alphanumeric outline, but with a different numbering system: 1, 1.1, 1.2, etc. Text is written as short notes rather than full sentences.

• 1.1.1 Sub-point of first point
• 1.1.2 Sub-point of first point
• 1.2 Second point

To write an effective research paper outline, it is important to pay attention to language. This is especially important if it is one you will show to your teacher or be assessed on.

There are four main considerations: parallelism, coordination, subordination and division.

Parallelism: Be consistent with grammatical form

Parallel structure or parallelism is the repetition of a particular grammatical form within a sentence, or in this case, between points and sub-points. This simply means that if the first point is a verb , the sub-point should also be a verb.

Example of parallelism:

• Include different regions, focusing on the different arguments from those against immunization

Coordination: Be aware of each point’s weight

Your chosen subheadings should hold the same significance as each other, as should all first sub-points, secondary sub-points, and so on.

Example of coordination:

• Include immunization figures in affected regions
• Illnesses that can result from the measles virus

Subordination: Work from general to specific

Subordination refers to the separation of general points from specific. Your main headings should be quite general, and each level of sub-point should become more specific.

Example of subordination:

Division: break information into sub-points.

Your headings should be divided into two or more subsections. There is no limit to how many subsections you can include under each heading, but keep in mind that the information will be structured into a paragraph during the writing stage, so you should not go overboard with the number of sub-points.

Ready to start writing or looking for guidance on a different step in the process? Read our step-by-step guide on how to write a research paper .

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Open Access

Peer-reviewed

Research Article

Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets

Contributed equally to this work with: Elodie Freymann, Fabien Schultz

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected] (EF); [email protected] (FS)

Affiliation Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, Department of Anthropology and Museum Ethnography, University of Oxford, Oxford, United Kingdom

Roles Supervision, Writing – review & editing

Affiliations Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, Department of Anthropology and Museum Ethnography, University of Oxford, Oxford, United Kingdom, Gorongosa National Park, Sofala, Mozambique, Interdisciplinary Centre for Archaeology and the Evolution of Human Behaviour, University of Algarve, Faro, Portugal

Roles Funding acquisition, Supervision, Writing – review & editing

Affiliations Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany, ZELT–Center for Nutrition and Food Technology gGmbH

Roles Formal analysis, Writing – original draft, Writing – review & editing

Affiliation Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany

Roles Resources, Supervision, Writing – review & editing

Affiliations Wild Minds Lab, School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom, Budongo Conservation Field Station, Masindi, Uganda

Affiliation Wildlife Research Center, Inuyama Campus, Kyoto University, Inuyama, Japan

Roles Investigation

Affiliation Budongo Conservation Field Station, Masindi, Uganda

Roles Formal analysis

Affiliations Budongo Conservation Field Station, Masindi, Uganda, Czech University of Life Sciences Prague, Prague, Czech Republic

Roles Resources, Writing – review & editing

Affiliations Budongo Conservation Field Station, Masindi, Uganda, Department of Comparative Cognition, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Writing – original draft, Writing – review & editing

Affiliations Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany, Pharmacognosy and Phytotherapy, School of Pharmacy, University College of London, London, United Kingdom

• Elodie Freymann, 
• Susana Carvalho, 
• Leif A. Garbe, 
• Dinda Dwi Ghazhelia, 
• Catherine Hobaiter, 
• Michael A. Huffman, 
• Geresomu Muhumuza, 
• Lena Schulz, 
• Daniel Sempebwa, 

• Published: June 20, 2024
• https://doi.org/10.1371/journal.pone.0305219
• Reader Comments

Wild chimpanzees consume a variety of plants to meet their dietary needs and maintain wellbeing. While some plants have obvious value, others are nutritionally poor and/or contain bioactive toxins which make ingestion costly. In some cases, these nutrient-poor resources are speculated to be medicinal, thought to help individuals combat illness. In this study, we observed two habituated chimpanzee communities living in the Budongo Forest, Uganda, and collected 17 botanical samples associated with putative self-medication behaviors (e.g., bark feeding, dead wood eating, and pith-stripping) or events (e.g., when consumer had elevated parasite load, abnormal urinalysis, or injury). In total, we selected plant parts from 13 species (nine trees and four herbaceous plants). Three extracts of different polarities were produced from each sample using n -hexane, ethyl acetate, and methanol/water (9/1, v/v ) and introduced to antibacterial and anti-inflammatory in vitro models. Extracts were evaluated for growth inhibition against a panel of multidrug-resistant clinical isolates of bacteria, including ESKAPE strains and cyclooxygenase-2 (COX-2) inhibition activity. Pharmacological results suggest that Budongo chimpanzees consume several species with potent medicinal properties. In the antibacterial library screen, 45 out of 53 extracts (88%) exhibited ≥40% inhibition at a concentration of 256 μg/mL. Of these active extracts, 41 (91%) showed activity at ≤256μg/mL in subsequent dose-response antibacterial experiments. The strongest antibacterial activity was achieved by the n- hexane extract of Alstonia boonei dead wood against Staphylococcus aureus (IC50: 16 μg/mL; MIC: 32 μg/mL) and Enterococcus faecium (IC50: 16 μg/mL; MIC: >256 μg/mL) and by the methanol-water extract of Khaya anthotheca bark and resin against E . faecium (IC50: 16 μg/mL; MIC: 32 μg/mL) and pathogenic Escherichia coli (IC50: 16 μg/mL; MIC: 256 μg/mL). We observed ingestion of both these species by highly parasitized individuals. K . anthotheca bark and resin were also targeted by individuals with indicators of infection and injuries. All plant species negatively affected growth of E . coli . In the anti-inflammatory COX-2 inhibition library screen, 17 out of 51 tested extracts (33%) showed ≥50% COX-2 inhibition at a concentration of 5 μg/mL. Several extracts also exhibited anti-inflammatory effects in COX-2 dose-response experiments. The K . anthotheca bark and resin methanol-water extract showed the most potent effects (IC50: 0.55 μg/mL), followed by the fern Christella parasitica methanol-water extract (IC50: 0.81 μg/mL). This fern species was consumed by an injured individual, a feeding behavior documented only once before in this population. These results, integrated with associated observations from eight months of behavioral data, provide further evidence for the presence of self-medicative resources in wild chimpanzee diets. This study addresses the challenge of distinguishing preventative medicinal food consumption from therapeutic self-medication by integrating pharmacological, observational, and health monitoring data—an essential interdisciplinary approach for advancing the field of zoopharmacognosy.

Citation: Freymann E, Carvalho S, Garbe LA, Dwi Ghazhelia D, Hobaiter C, Huffman MA, et al. (2024) Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets. PLoS ONE 19(6): e0305219. https://doi.org/10.1371/journal.pone.0305219

Editor: Armel Jackson Seukep, University of Buea, CAMEROON

Received: January 9, 2024; Accepted: May 25, 2024; Published: June 20, 2024

Copyright: © 2024 Freymann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: Funding for this project was granted by the the Clarendon Fund at the University of Oxford (to EF), the British Institute of Eastern Africa (to EF), Keble College at the University of Oxford (to EF), Boise Trust Fund (to EF), German Federal Ministry of Education and Research (13FH026IX5, PI: L-AG and Co-I: FS) (to LAG, FS) and Neubrandenburg University of Applied Sciences (grant # 13310510) (to LAG, FS).

Competing interests: The authors have declared that no competing interests exist.

Introduction

‘Medicinal foods’ refer to resources in the diet that have potential curative value due to the presence of plant secondary metabolites (PSMs) [ 1 , 2 ]. PSMs are compounds that usually occur only in special, differentiated cells [ 3 ] and which help plants defend against predators, pathogens, and competitors [ 4 – 7 ]. PSMs can have a range of functions, including the inhibition of microbial, fungal, and competitor growth [ 8 ]. While some PSMs can be toxic at high doses, these compounds can also promote the health of human and non-human consumers [ 8 – 10 ]. Research suggests 15–25% of primate and other mammalian diets consist of medicinal foods [ 9 , 11 ]. These resources likely play a critical role in animal health-maintenance by passively preventing or reducing the impact of parasitic infections or other pathogens [ 9 – 14 ].

While most animals likely consume foods with medicinal properties as part of their normal diets, fewer species have been shown to engage in therapeutic self-medication. Huffman [ 15 ] defines this type of self-medicative behavior as the active extraction and ingestion, by an ill individual, of medicinal resources with little nutritional value. Instead of an individual passively benefiting from a plant’s medicinal properties through normal feeding, this form of self-medication requires basic awareness of the resource’s healing properties. One of the best-studied animals to engage in this form of self-medication is our closest living relative: the chimpanzee.

Wild chimpanzees ( Pan troglodytes ), across at least sixteen field sites [ 15 ] have demonstrated therapeutic self-medication using two well-established self-medicative behaviors: leaf swallowing [ 16 , 17 ] and bitter-pith chewing [ 18 ]. Leaf swallowing, first reported by Wrangham [ 19 , 20 ] and described by Wrangham & Nishida [ 21 ], involves the careful selection and ingestion of whole, hispid leaves. This behavior was later demonstrated to expel internal parasites (i.e. Oesophagostomum sp. and Bertiella studeri ) from the gut [ 16 , 17 , 22 , 23 ]. The functional mechanism responsible for this anthelminthic effect is considered to be primarily “mechanical” [ 9 ] as, rather than a chemical compound, the leaf’s indigestibility, brought about by the trichomes on its surface—stimulates gut motility in the swallower [ 17 , 23 , 24 ].

The second established behavior is bitter-pith chewing, which involves the stripping of outer bark and leaves from the soft new stem growth of the shrub, Vernonia amygdalina , exposing the inner pith. Individuals chew the pith and ingest only the bitter juices while spitting out the fibers [ 18 , 25 ]. Bitter-pith chewing is considered ‘phytochemical’ self-medication [ 9 ], as its anthelminthic effect appears to be the result of bioactive PSMs [ 26 – 29 ]. This behavior’s medicinal effect was associated with a significant drop in the infection intensity of Oesophagostomum stephanostomum nematodes [ 25 ], suggesting that the bitter compounds directly affect the adult worms. This hypothesis was supported by in vivo studies conducted by Jisaka et al. [ 30 ], demonstrating that extracts from the pith permanently paralyzed adult Schistosome parasites. V . amygdalina is also used to aid gastrointestinal discomfort and other signs of parasitosis in humans and livestock, symptoms also displayed by chimpanzees ingesting the plant’s bitter pith [ 9 , 18 , 25 , 31 ]. The bitter piths of other plant species are reported to be chewed by chimpanzees across field sites but detailed studies on their medicinal properties have yet to be conducted [ 9 ].

Beyond these two established behaviors, not much is known about the phytochemical self-medicative repertoires of wild chimpanzees, although some behaviors associated with the ingestion of specific plant parts or processing techniques have been recommended for further investigation [ 9 , 15 , 32 ]. One of these behaviors is bark feeding, which involves the ingestion of living stem bark and/or cambium [ 33 ], and which has been observed in at least eleven established field sites [ 33 – 43 ]. Bark feeding has been suggested as a medicinal behavior in chimpanzees and other primates, used to aid in the chemical control of intestinal nematode infection and to relieve gastrointestinal upset [ 9 ]. Bark is characteristically highly fibrous, heavily lignified, sometimes toxic, relatively indigestible, and nutrient-poor [ 44 ]. However, the contribution of bark in chimpanzee diets and toward general health is still poorly understood [though see: 45 ]. In this study, the bark of eight species ingested by Budongo chimpanzees ( Scutia myrtina , Cynometra alexandri , Alstonia boonei , Ficus exasperata , Ficus variifolia , Syzygium guineense , Desplatsia dewevrei , Khaya anthotheca) was screened for antibiotic and anti-inflammatory properties, to better understand the function of bark feeding behaviors and the role this behavior may play in the health maintenance of chimpanzees. For the species K . anthotheca , we tested a mixture of bark and congealed resin, which Budongo chimpanzees were observed to particularly target throughout the study period.

Another putative self-medicative behavior is dead wood eating [ 9 , 35 ], which involves the consumption of decomposing cambium from dead trees. To date, the majority of studies examining this behavior in apes have focused on exploring potential mineral and nutritional benefits, rather than investigating pharmacological properties [ 46 – 49 ]. Many of these studies suggest that dead wood is exploited by chimpanzees as a source of sodium in environments where this mineral is otherwise scarce [ 48 , 49 ]. Our study evaluates the pharmacology of two species of dead wood ( A . boonei and Cleistopholis patens) consumed by the Sonso community of chimpanzees to determine whether this behavior may have multiple functions or health benefits.

The ingestion of pith material from other species has also been suggested as putatively self-medicative [ 34 , 50 , 51 ]. However, unlike V . amygdalina bitter-pith, some of these plant piths appear bland or tasteless. While Wrangham et al. have previously suggested that pith is likely a high-fiber fallback food [ 52 ], De la Fuente et al. review several pith species targeted by chimpanzees with proposed medicinal properties [ 32 ]. In our study, two species of non-bitter piths ( Marantachloa leucantha and Acanthus polystachyus) , were collected for pharmacological assessment. M . leucantha was observed on several occasions being stripped, masticated, and spat out after the juice was extracted from the pith, whereas A . polystachyus was observed being stripped, masticated, and swallowed. Both of these species are also ingested by chimpanzees in Kibale National Park, Uganda [ 52 ].

Establishing phytochemical self-medicative behaviors in wild animals is difficult and time consuming, as the burden of proof is high, self-medicative events can be rare relative to other behaviors, and methods often require multidisciplinary expertise and collaboration [ 9 ]. Past studies have utilized ethnopharmacological methods to determine specific medicinal properties of foods consumed by primates [ 11 ], greatly advancing our understanding of the relationship between primate diets and health. However, a key challenge for establishing novel self-medicative behaviors is differentiating between medicinal food consumption and therapeutic self-medication. While pharmacological data interpreted on its own is crucial for establishing the presence of medicinal resources in chimpanzee diets, the integration of observational and health monitoring data is needed to parse therapeutic self-medicative behaviors from normal feeding behaviors with inadvertent health benefits. Furthermore, the importance of collecting in situ samples from the locations where putative self-medicative behaviors are observed is paramount, as ecological, climatic, and anthropogenic variables can cause variation in the bioactivity of plants across habitats [ 53 ].

In total, we investigated the bioactivity of 51 plant extracts produced from 17 part-specific samples (across 13 species), collected in the Budongo Forest. Each extract was tested for inhibition of bacterial growth as well as anti-inflammatory COX-2 inhibition activity. Due to limitations in scope, funding, and the unavailability of anthelminthic assays for wild animal parasites, none were not conducted in this study, restricting specific identification of parasiticidal behaviors. Assay results are reported and contextualized in this study with direct behavioral evidence and health monitoring data.

Materials and method

Study site and subjects.

Behavioral data, health monitoring metrics, and botanical samples were collected from the Budongo Central Forest Reserve in Uganda (1°35′– 1°55′ N, 31°18′–31°42′ E). An overview of methodological workflow can be found in S2 Fig . The Budongo Conservation Field Station (BCFS) site, founded in 1990, is composed of continuous, semi-deciduous forest and contains two habituated Eastern chimpanzee ( Pan troglodytes schweinfurthii ) communities [ 54 ]. The Sonso community has been studied continuously since 1992, and the ages, social relationships, demographics, and diet of its members are well documented [ 55 , 56 ]. The Sonso population was ~68 individuals at the time of data collection, and the home range covered an area of ~5.33 km 2 [ 57 ]. Waibira, a larger group of at least 105 individuals, was more recently habituated, with consistent data collection beginning in 2011. The Waibira maximum home range area was ~10.28 km 2 [ 57 ].

Behavioral data collection

All samples were collected in the Budongo Forest within the Sonso home range, based on behavioral observations from the study period and supporting evidence from the site’s long-term data of their use. Behavioral and health data were collected from two neighboring chimpanzee communities, each for one four-month field season (Sonso: June-October 2021, Waibira: June-October 2022). Data collected between June-September 2021 informed subsequent plant sample collection for pharmacological analysis, which occurred in early September 2021. Behavioral data collected after sample collection provided additional behavioral context for ingestion of these species. Behavioral data were collected between 07:00 and 16:30 in Sonso and between 06:30 and 17:00 in Waibira using day-long focal animal follows sensu Altman et al. [ 58 ]. This data was recorded using Animal Observer (AO) on iPad and ad libitum feeding events were recorded for any unusual feeding behaviors, including but not limited to bark ingestion, dead wood eating, pith stripping, and geophagy. All feeding events were filmed on a Sony Handycam CX250. We prioritized focal follows on individuals with wounds, high or diverse parasite loads identified through on-going monitoring, or known ailments. However, consecutive day follows of priority individuals were not always possible—or were avoided when they might contribute to increased stress in particularly vulnerable individuals. Throughout the study, using this protocol, 27 Sonso individuals (♂:11; ♀:16) and 24 Waibira individuals (♂:14; ♀:10) were observed. Authors collecting behavioral data were blind to pharmacological results during both study periods.

Health monitoring

Individual health data were recorded in both communities, including opportunistic macroscopic and microscopic fecal analysis and urinalysis testing. While anthelminthic assays were not run in this study, parasite load was opportunistically assessed to provide additional health context for each observation. As the presence of certain helminths may impair a host’s immunological response to bacterial, viral, and protozoal pathogens [ 59 ], parasite load can provide a proxy measurement for overall health. Similarly, a reduced immune system and increased stress caused by co-infections could render a host more susceptible to virulent endoparasites [ 60 , 61 ]. When helminths and/or proglottids were found in samples, they were collected and preserved in ethanol for later identification. To quantify parasite loads, fecal samples were analyzed using the McMaster Method [ 9 , 25 , 62 ]. Urinalysis samples were taken opportunistically using multi-reagent Urine Dipstick Test 9-RC for Urotron RL9 to assess the health and physiological status of group members following methods established by Kaur & Huffman [ 63 ]. Urinalysis metrics considered in this study included: leukocytes (LEU) associated with pyuria caused by UTI, balanitis, urethritis, tuberculosis, bladder tumors, viral infections, nephrolithiasis, foreign bodies, exercise, glomerulonephritis, and corticosteroid and cyclophosphamide use; blood (BLO) associated with peroxidase activity of erythrocytes, and UTIs; and ketones (KET) associated with pregnancy, carbohydrate-free diets, starvation, and diabetes [ 64 ]. Test results were interpreted in situ using a colorimetric scale. We considered a result ‘abnormal’ if the colorimetric scale indicated a positive result when the expected result was negative or if the result was outside the specified test parameters according to the manufacturer.

Plant sample selection for bioactivity testing

Plants were selected for pharmacological testing after three months of data collection in the Sonso community. We selected 10 samples (from 9 species) based on direct observations during this period. These observations included individuals targeting plant parts associated with putative self-medicative behaviors (i.e., bark feeding, dead wood eating, pith-stripping) or sick/wounded individuals seeking out unusually consumed resources. We then selected an additional five species, the ingestion of which had not been directly observed, for testing based on their historical inclusion in Sonso chimpanzees’ bark feeding repertoire. GM, who has worked at the field station for over thirty-years, has previously observed bark feeding on each of these selected species. These historic observations enabled collection of bark samples from specific trees known to have been previously stripped. In two cases, leaf samples were collected from tree species that were also selected for bark samples ( S . guineense and F . exasperata) . While neither Sonso nor Waibira chimpanzees have been observed ingesting the leaves of S . guineense , a sample was collected to enable comparison of bioactivity across plant parts. F . exasperata leaves are consumed in both communities; however, we found no behavioral evidence for use in unusual contexts. In some cases, direct observation of an event involving one of the collected species occurred after botanical collection was complete. These post hoc behavioral observations are reported in this paper, although they did not impact sample selection.

Collection of sample material

Plants were collected from the Sonso community home range following best practice procedures [ 65 ], using sustainable harvesting methods [ 66 ]. See S1 File for more information. Voucher accession numbers are reported in Table 3 . Digital images of voucher specimens can be found in S3 Fig . The currently recognized scientific names of each species were confirmed on https://mpns.science.kew.org/ . Plant family assignments were done in accordance with The Angiosperm Phylogeny Group IV guidance [ 67 ].

Ethnobotanical literature review

We conducted a post-hoc ethnomedicinal review of all species collected for this study using Google Scholar, PROTA, and Kokwaro’s ethnomedicinal pharmacopeia [ 68 ]. To search databases, we used scientific names and synonyms for each plant as keywords [ 65 ].

Plant processing and extractions

At Neubrandenburg University of Applied Sciences, samples were ground using a food processor. Extractions were produced using two solvents and a solvent mixture ( n -hexane, ethyl acetate, and methanol/water ( v/v 9/1)), allowing for the selective isolation of components with varying solubilities and polarities. Methanol-water, the solvent with the highest polarity, generally extracts primary plant metabolites (e.g., polar compounds such as proteins, amino acids, and carbohydrates). Nonpolar solvents like n- hexane extract nonpolar compounds like lipids, making n-hexane a preferred solvent for oil or wax extraction. Extractions with each solvent were achieved through double maceration of new material (non-successively). Extraction suspensions were placed on a shaker at 80 rpm at room temperature for minimum 72h, followed by vacuum filtration. Processes were repeated with the leached material. Filtrates were then combined and dried using a vacuum evaporator, labeled, and stored at -20°C until needed for assays.

Sample solution preparation

To create sample solutions, each crude extract was dissolved in DMSO (Carl Roth) at a concentration of 10 mg/mL. To ensure a homogenous solution, samples were mixed with a vortex mixer and, if necessary, treated with sonication at room temperature or up to 55°C for samples with low solubility. Each extract solution was then tested for inhibition of bacterial growth as well as anti-inflammatory COX-2 inhibition activity. Solutions were stored at -20°C when not in use.

Antibacterial susceptibility tests

A. bacterial strains..

For antibacterial assays, eleven multidrug-resistant clinical isolate strains from nine species were used. This process increased the study’s applicability for early-stage drug discovery, specifically relevant to the threat of antimicrobial resistance (AMR). Seven of these strains (from six species) are classified as ESKAPE pathogens, including Enterococcus faecium (DSM 13590), Staphylococcus aureus (DSM 1104; DSM 18827), Klebsiella pneumoniae (DSM 16609), Acinetobacter baumannii (DSM 102929), Pseudomonas aeruginosa (DSM 1117), and Enterobacter cloacae (DSM 30054), meaning they are highly virulent and resistant to antibiotics [ 69 ]. A strain of the foodborne pathogen Escherichia coli (DSM 498) with AMR as well as a non-resistant E . coli strain (DSM 1576) were also included in the study. Although not an ESKAPE pathogen, E . coli is widely known for causing bacterial diarrhea and AMR strains are a major cause of urinary tract infections [ 70 , 71 ]. Strains of Stenotrophomonas maltophilia (DSM 50170) and Salmonella enterica subsp. enterica (DSM 11320) were also tested. More information on specific clinical isolates/strains, their individual resistance profiles, and antibiotics used can be found in the S5 & S6 Tables in S2 File . Clinical and Laboratory Standards Institute (CLSI) guidelines for broth microdilution testing (M100-S23) were followed [ 72 ].

b. Growth inhibition screening and dose-response study.

The broth dilution in vitro methods for bacterial susceptibility assessment have previously been described by Schultz et al. [ 69 ]. The standardized bacterial working cultures were pipetted into sterile 96-well microtiter plates (Greiner Bio-One International, CELLSTAR 655185). Extracts and antibiotic (64–1 μg/mL), vehicle and sterility controls, were then added into respective wells. Initial optical density measurement (600 nm) was performed, accounting for absorbance of extracts. Plates were incubated at 37°C for 18 h, except for A . baumannii which was incubated for 22h in accordance with strain characteristics ( S5 Table in S2 File ) . After incubation, a final optical density reading (600 nm) was conducted. Percent inhibition values were calculated and the IC 50 and MIC values were determined [ 69 , 73 ]. The IC 50 value is defined as the lowest concentration at which an extract showed ≥ 50% inhibition, and the MIC is the lowest concentration at which an extract displayed ≥ 90% inhibition. A total of 51 samples underwent single-dose pre-screening for growth inhibition (in triplicate) at the concentration of 256 μg/mL on eleven pathogens. Samples showing ≥40% growth inhibition were further tested in a dose-response study with two-fold serial dilution at descending concentrations from 256 to 4 μg/mL. The dose-response experiments were done as biological replicates on separate days in triplicate (technical replicates) to validate reproducibility. Positive controls (antibiotics) and negative controls (vehicle control and sterile media control) were always included. Further details on bacteria standardization can be found in S1 File . Information on plate setup for bacterial library screens and dose-response assays can be found in S4 Fig .

COX-2 inhibition assay

Anti-inflammatory assays were assessed using an in vitro COX inhibitor screening assay kit (Cayman Item No: 701080), with modifications previously described in Schultz et al. [ 74 ]. All extracts were first screened in duplicate for inhibition against human recombinant COX-2 at an initial concentration of 50 μg/mL. For extracts exhibiting at least 50% inhibition, the concentration was then lowered to 10 μg/mL, 5 μg/mL, and 2.5 μg/mL. The most active extracts were taken to dose-response experiments for determination of IC 50 values ( Table 5 ). The assay was done in two steps: 1) the COX reaction step in which the prostaglandin H 2 (PG) was produced (which was further reduced to the more stable prostaglandin F 2α by addition of stannous chloride), and 2) an acetyl choline esterase competitive ELISA step to quantify the produced prostaglandin and calculate a potential enzyme inhibition caused by the extracts. The pure compound and selective COX-2 inhibitor DuP-769 was included as a positive control. DMSO was included as the vehicle control for determining 100% enzyme activity. Information on ELISA plate setup for anti-inflammation assays can be found in S5 Fig .

Ethics statements

Behavioral data used in this study were collected with the approval of the Uganda Wildlife Authority (permit #: COD/96/05) and the Uganda National Council for Science and Technology (permit #: NS257ES). Exportation of samples for pharmacological testing were conducted under UNCST permit #: NS104ES. Behavioral data collection adhered to International Primatological Society’s Code of Best Practice for Field Primatology [ 75 ]. No exported samples were listed under CITES. Plant samples were exported in collaboration with Makerere University (permit #: UQIS00005033/93/PC), issued by the Ugandan government, and transported to Neubrandenburg University of Applied Sciences in accordance with the Nagoya Protocol. A CUREC was approved by the University of Oxford (Ref No.: SAME_C1A_22_080). The authors report no conflict of interest.

Behavioral observations

Several unusual feeding events and putative self-medicative behaviors were recorded over 116 total field days. Table 1 reports all species collected for pharmacological testing and provides behavioral justifications for collection. Images from some of these events can be found in S1 Fig .

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https://doi.org/10.1371/journal.pone.0305219.t001

Individuals with injuries were directly observed ingesting K . anthotheca bark and resin, W . elongata young leaves, C . alexandri bark, and C . parasitica ferns. Individuals exhibiting respiratory symptoms were observed ingesting C . alexandri bark and K . anthotheca bark and resin. Individuals with abnormal urinalysis results (e.g., positive for leukocytes, elevated ketones, and presence of blood) were observed feeding on C . patens dead wood, K . anthotheca bark and resin, and M . leucantha pith. Individuals with recent cases of diarrhea were observed consuming A . boonei and C . patens dead wood, K . anthotheca bark and resin, and W . elongata leaves. Parasitological analyses further suggest individuals with varying degrees of endoparasite infections consumed S . myrtina and C . alexanderi bark, A . boonei and C . patens dead wood, K . anthotheca bark and resin, W . elongata leaves, as well as A . polystachyus and M . leucantha pith. On a day when two individuals were observed leaf swallowing, a scientifically established self-medicative behavior, one was observed consuming K . anthotheca bark and resin, while the other was observed stripping A . polystachyus pith prior to the event. Ingestion of F . variifolia , D . dewevrei , and S . guineense bark were never directly observed during the study period. Examples of bark feeding, dead wood eating, and pith-stripping marks are shown in Fig 1 .

[ a ]: Evidence of F. exasperata bark feeding [ b ] Evidence of C. patens dead wood eating [ c ] Evidence M. leucantha pith-stripping and wadging.

https://doi.org/10.1371/journal.pone.0305219.g001

Ethnobotanical review

Based on our analysis of ethnomedicinal literature spanning various African regions from 1976 to 2022, 11 out of the 13 species tested also had documented ethnomedicinal uses ( Table 2 ).

https://doi.org/10.1371/journal.pone.0305219.t002

Production of extracts and sample information

Taxonomic information and extraction details for the 13 plant species studied, including the plant family, local name (when available), plant part used, solvent for extraction, yield of extraction, extract identification numbers (extract IDs), herbarium accession numbers, and collection location are summarized in Table 3 . Overall, the highest extraction yields were obtained with methanol-water (9/1) as a solvent. The yields from methanol-water extractions for C . parasitica , F . exasperata leaves, and S . guineense stem bark were higher than the other extractions from these samples. The plant samples which had higher yield values with n -hexane, such as the leaves of W . elongata and bark extract of A . boonei , likely have a higher content of lipids (i.e., fatty molecules).

https://doi.org/10.1371/journal.pone.0305219.t003

Library screening against multidrug-resistant human and food bacterial pathogens

Initial screening of extracts involved checking for growth inhibition against each bacterium at a concentration of 256 μg/mL. In total, 45 of the 51 plant extracts (88%) showed activity ≥40% inhibition against at least one of the 11 strains and were thus considered active and brought to dose-response experiments to determine their IC 50 value and MIC. Results from the library screening are reported in S1 Table in S2 File . As all tested plant species in the library screen had at least one extract that was active ( in vitro ) against at least one bacterial strain, no entire species was eliminated for further experimentation. However, as no extracts (at any concentration) inhibited the growth of K . pneumoniae , no further tests were conducted on this bacterium. The extract active against the most bacterial strains (n = 11) was the methanol-water extract of S . guineense stem bark (mwE098a, active against eight strains), followed by the methanol-water S . guineense leaves (mwE098b), the ethyl acetate P . patens dead wood, and the n -hexane A . boonei dead wood (hE092b) extracts, which were each active against seven, seven, and six strains, respectively. The only extract that demonstrated significant inhibition against P . aeruginosa at the highest test concentration was the methanol-water extract from S . guineense bark (mwE098a). This was also the only extract to display significant inhibition at 256 μg/mL against E . cloacae . Of all bacteria in this study, the two strains of E . coli (DSM 498 and DSM 15076) were the most susceptible, with at least one extract from all plant species inhibiting their growth. The E . coli strain with nine known antibiotic resistances (DSM 15076) surprisingly showed growth inhibition in 80% of tested extracts.

Dose-response antibacterial experiments

In dose-response assays, 41 out of the 45 tested extracts (91%) showed activity at ≤256μg/mL, though not all extracts reached MIC values (see Table 4 ). The results, along with standard deviations, are reported in S2 Table in S2 File , while S3 Table in S2 File provides a summary of the number of strains each extract was active against. The strongest in vitro growth inhibition was reported for the methanol-water extract of K . anthotheca bark and resin (mwE088) against Gram-positive E . faecium and the n- hexane extract of A . boonei dead wood (hE092b) against Gram-positive S . aureus (DSM 1104). Both extracts had low IC 50 values of 16 μg/mL (showing strong inhibition), with MIC values of 32 μg/mL against respective strains. E . faecium showed the most general susceptibility to K . anthotheca , with all extracts of this species achieving MIC values (mwE088: 32 μg/mL, eE088: 64 μg/mL, hE088: 128 μg/mL). The ethyl acetate extract of A . boonei dead wood (eE092b) also strongly inhibited the growth of E . faecium (IC 50 : 16 μg/mL; MIC: 64 μg/mL), as did the n- hexane extract of A . boonei dead wood, producing an IC 50 value of 16 μg/mL but failing to reach a MIC value. S . aureus (DSM 1104) was also highly susceptible to the ethyl acetate extracts of A . boonei dead wood (IC 50 : 32 μg/mL; MIC: 128 μg/mL).

https://doi.org/10.1371/journal.pone.0305219.t004

Only one extract, the methanol-water extract of S . guineense bark (mwE098a), was active against the gram-negative P . aeruginosa . This extract exhibited moderate growth inhibition (IC 50 : 64 μg/mL) with no MIC value reached. Despite E . coli (DSM 498) being highly susceptible on the library screen, only two extracts, the methanol-water extract of A . boonei dead wood (mwE092b; IC 50 : 256 μg/mL) and the methanol-water extract of S . guineense leaves (mwE098b; IC 50 : 128 μg/mL), reached IC 50 values at the concentration range tested, with no MICs reached. Interestingly, the strain of E . coli with nine known resistances (DSM 1576) was more susceptible, with 89% (N = 40) of extracts achieving IC 50 values ≤ 256 μg/mL. The most active extract against this strain was the methanol-water extract of K . anthotheca (mwE088; IC 50 : 16 μg/mL; MIC: 256 μg/mL). S . guineense exhibited the highest overall inhibition of S . maltophilia , with all extracts except hE098a displaying IC 50 values of ≤ 256 μg/mL against the bacterium. At the concentration range tested, no extracts yielded MIC values for S . aureus (DSM 18827), A . baumannii , E . cloacae , P . aeruginosa or E . coli (DSM 498).

Anti-inflammatory COX-2 inhibition library screen

Results from the in vitro COX-2 inhibition library screen at descending concentrations are reported in S4 Table in S2 File . At the initial concentration of 50 μg/mL, 43 out of 51 extracts (84%) exhibited an enzyme inhibition of at least 50%, displaying anti-inflammatory activity. This included at least one extract of every plant species. In the next stage of screening, at 10 μg/mL, 18 samples were eliminated. During the final step, at 5 μg/mL, five more were eliminated. The remaining 17 extracts from 10 plant species which displayed inhibition ≥50% at 5 μg/mL, were then introduced to dose-response experiments. The ethyl acetate S . myrtina bark extract (eE089b) was taken to the COX-2 dose-response despite not showing inhibition past 50 μg/mL, as it almost reached the selection limit during analysis and had a relatively high standard deviation. No extracts from W . elongata , C . patens or D . dewevrei showed COX-2 inhibition at 5 μg/mL and thus were excluded from further testing.

COX-2 inhibition dose-response experiments

The most active COX-2 inhibitors were extracts from K . anthotheca (mwE088; hE088; eE088), C . parasitica (mwE087; hE087), F . exasperata (hE093a; eE093a), S . myrtina (hE089a; eE089b), F . variifolia (eE097; hE097), A . polystachyus (hE099; eE099), M . leucantha (hE094), S . guineense (hE098a), A . boonei (hE092b), and C . alexandri (hE096). Results are reported in Table 5 . The strongest COX-2 inhibitor was the K . anthotheca methanol-water bark and resin extract (mwE088) (IC 50 of 0.55 μg/mL), followed by the C . parasitica methanol-water fern extract (mwE087) (IC 50 of 0.81 μg/mL). In contrast, all extracts of the species W . elongata , C . patens , and D . dewevrei failed to show ≥50% inhibition, mostly at the second screening concentration (10 μg/mL). W . elongata extracts notably showed low activity in both antibacterial and COX-2 inhibition assays.

https://doi.org/10.1371/journal.pone.0305219.t005

Plant species with strong pharmacological activity

This study provides the first pharmacological and behavioral evidence of its kind, based on in situ sampling, for the medicinal benefits of bark feeding, dead wood eating, and non-bitter pith stripping behaviors in Budongo chimpanzees. In the following sub-sections, we describe and discuss specific results from five of the tested plant species in further detail. For scope, we selected the two species with the strongest antibacterial properties ( K . anthotheca and A . boonei ) to profile, both of which were the only species to reach 40% inhibition at 16 μg/mL. We also selected C . parasitica to discuss as this species, along with K . anthotheca , exhibited the strongest anti-inflammatory properties. We then discuss results from our S . guineense samples, as this species was effective against the most bacterial strains in our antibacterial assays. Lastly, we selected S . myrtina , as we have behavioral evidence and health data that anecdotally support the use of this species for therapeutic self-medication by Budongo chimpanzees.

Alstonia boonei . Numerous in vitro and in vivo studies, reviewed by Adotey [ 76 ], have reported pharmacological activity in A . boonei bark. However, none of these studies investigated dead wood samples of A . boonei . Consistent with these findings, we found high levels of antibacterial and anti-inflammatory activity in the extracts of this species. Interestingly, extracts from A . boonei dead wood generally exhibited higher activity than living bark. This difference could be due either to a change in active ingredient composition, or possible fungal growth following the tree’s death. While the A . boonei dead wood n -hexane extract (hE092b) exhibited strong growth inhibition against S . aureus (DSM 1104; DSM 18827) and E . faecium at low concentrations in the dose-response assays, the n -hexane bark extract (hE092a) showed no activity <256 μg/mL. Similarly, the ethyl acetate extract of dead wood (eE092b) also strongly inhibited S . aureus (DSM 1104) (IC 50 : 16 μg/mL; MIC: 128 μg/mL) and E . faecium (IC 50 : 16 μg/mL; MIC: 64 μg/mL), while the ethyl acetate bark extract of this species did not even exhibit enough inhibition in the antibacterial library screen to be taken to dose-response assays. However, the methanol-water extract of A . boonei bark (mwE092a) did show activity against E . coli (DSM 498) (IC 50 : 128 μg/mL), as did the methanol-water dead wood extract (mwE092a) (IC 50 : 128 μg/mL), with no MIC values reached in either case. Overall, extracts from A . boonei displayed more potent activity in Gram-positive bacteria, although this effect is more apparent in dead wood than stem bark. In the COX-2 inhibition assays, the n -hexane extract of A . boonei dead wood also showed strong anti-inflammatory inhibition, while the n -hexane extract of the bark only exhibited weak inhibition (at the highest test concentration of 50 μg/mL).

A . boonei is a known medicinal plant across East Africa, commonly used for a variety of reproductive, bacterial, and gastro-intestinal issues, as well as for snake bites, asthma, and dizziness [ 68 , 76 , 77 ]. The bark and latex are intensely bitter, a reliable signal of the presence of bioactive secondary compounds and toxicity [ 94 – 96 ]. Budongo chimpanzees in both communities have been reported to consume both bark and dead wood of A . boonei , often travelling long distances to access these trees and only consuming small amounts of bark per feeding bout [ 45 ]. In an observation reported in this study (see Table 1 : A . boonei , Case 1 ), three males ingested A . boonei dead wood while outside the community’s core area for 1-minute. Two days before the event, one of the individuals had been observed with diarrhea, while also shedding visible tapeworm proglottids ( Bertiella sp.). This sample also contained unidentified protozoa, and Taenia sp. eggs. Pebsworth et al. [ 34 ] also reported an event in which four adult males, all with diverse parasite loads, traveled to a large A . boonei tree and ingested bark.

In the long-term site data, A . boonei bark ingestion was only documented 17 times between 2008–2021 [ 45 ], although this behavior was not systematically reported. In addition, the direct observation of only one A . boonei dead wood eating event, and no A . boonei bark ingesting events over the two four-month periods of observation in this study, suggest that consumption of this species is relatively rare across both communities. While specific pathogenic catalysts for selection of this species remain unknown, based on pharmacological, ethnobotanical, and behavioral data, we propose that A . boonei may be a therapeutic self-medicative resource for Budongo chimpanzees. The relatively strong inhibitory activity of this species against S . aureus , a bacteria associated with causing contamination on the skin leading to chronic wounds [ 97 ], as well as its anti-inflammatory properties, suggests that A . boonei ingestion may have beneficial effects in wound care contexts.

Khaya anthotheca . Previous studies have demonstrated that K . anthotheca bark contains biologically active compounds like gedunins, mexicanolide, phragmalin, and andirobins [ 98 ]. One limonoid identified in the species, anthothecol, has anti-cancer properties [ 99 ]. A study by Obbo et al. [ 100 ] on K . anthotheca bark collected in the Budongo Forest, found strong antiprotozoal activity against Plasmodium falciparum (IC 50 0.96 μg/mL) and Trypanosoma brucei rhodesiense (IC 50 5.72 μg/mL). A related species, K . senegalensis , has been shown to cause cell lysis in some gram-negative bacteria, including Salmonella Typhimurium , Escherichia coli , Shigella sp. and Salmonella sp., by targeting cytoplasmic membranes [ 101 ].

In our antibacterial library screen, of all extracts tested, only the methanol-water extract inhibited growth of A . baumannii (although no IC 50 values were reached in dose-response). The methanol-water extract also inhibited the growth of E . coli (DSM 498) in the library screen, as did the ethyl acetate (eE088) extract, though again no IC 50 values were reached. In our antibacterial dose-response assays, all extracts of K . anthotheca stem bark and resin exhibited strong inhibition against the Gram-positive E . faecium . The most active extract against this strain, which was also the strongest antibacterial result reported in this study, was methanol-water (mwE088) (IC 50 : 16 μg/mL; MIC: 32 μg/mL). All extracts of this species were also found to inhibit E . coli (DSM 1576) in the dose-response experiments, with the methanol-water extract once again also showing the strongest inhibition (IC 50 : 16 μg/mL; MIC: 256 μg/mL). This extract also inhibited the growth of S . maltophilia (IC 50 : 64 μg/mL) in the library screen. Only weak inhibition was found against the food pathogen S . enterica ( n -hexane extract, IC 50 : 256 μg/mL).

K . anthotheca exhibited potent anti-inflammatory activity. Of all extracts tested, the methanol-water K . anthotheca extract (mwE088) displayed the strongest COX-2 inhibition activity (IC 50 : 0.55 μg/mL). Past phytochemical studies on methanol and ethanol-water stem bark extracts from the related species, K . senegalensis , revealed many phenolic compounds, including flavonoids and tannins e.g., [ 101 , 102 ]. Flavonoids act on the inflammatory response, and may block molecules like COXs, cytokines, nuclear factor-кB and matrix metalloproteinases [ 103 ]. Some tannins have also been proven to have strong free radical-scavenging and antioxidant activities [ 104 ]. These compounds are antagonists of particular hormone receptors or inhibitors of particular enzymes such as COX enzymes [ 103 ]. If Khaya species are phytochemically similar, this could help explain K . anthotheca ’s strong COX-2 inhibitory activity.

Across Africa, K . anthotheca is traditionally used for ailments including allergies, fever, headaches, jaundice, bacterial infections, and as a disinfectant for bleeding wounds [ 105 – 107 ]. Our behavioral observations suggest that this species is also a common resource for Sonso chimpanzees, with a total of 65 feeding events recorded throughout the first field season. Of these events, several involved individuals with imbalanced health states (see Table 1 : K . anthotheca ) . On at least three independent occasions, K . anthotheca bark and resin were consumed by wounded individuals. Two adult females on different days tested positive for leukocytes on urinalysis tests within hours of ingesting K . anthotheca , suggesting the presence of infection. One of these individuals was also experiencing severe diarrhea the day prior, the other was found to have trace levels of blood in her urine. A juvenile female with a persistent cough was also observed consuming K . anthotheca bark. On several occasions individuals with high parasite loads or diverse species infection were observed targeting this resource while shedding tapeworm proglottids ( Bertiella sp.). An elderly female was also observed eating bark and resin a few hours prior to leaf-swallowing, a well-established self-medicative behavior known to rid the gut of endoparasites [ 9 , 23 ]. The frequency of K . anthotheca ingestion in the Sonso diet during this period, suggests that individuals have consistent exposure to the antibacterial and anti-inflammatory compounds present in this species. Whether this is a case of passive prevention through intake of a medicinal food, or therapeutic self-medication for a common and wide-spread condition will need further investigation. If used therapeutically, our results suggest this species could be used for treating wounds, bacterial or infections, and/or reducing internal parasite loads.

Christella parasitica.

Extracts of C . parasitica produced notably high anti-inflammatory activity in COX-2 testing, with the methanol-water extract (mwE087) achieving an IC 50 value of 0.81 μg/mL. This same extract, however, exhibited the lowest general activity in the antibacterial library screen. The only antibacterial activity from this species was on E . coli (DSM 498) by the ethyl acetate and n- hexane extracts (eE087; hE087), and on E . coli (DSM 1576) by the n-hexane extract (hE087). The n -hexane extract reached an IC 50 of 128 μg/mL in dose-response assays with no MIC value. Prior to this study, there had been limited pharmacological testing on C . parasitica (though see [ 108 ]), so comparison across studies is not possible.

When we considered the associated behavioral observation involving C . parasitica , we found a notable relevance to our pharmacological results (see Table 1 : C . parasitica , Case 1 ). This observation involved a wounded Sonso adult male (PS) travelling outside of his core area with a large group. It was unclear if this was an inter-community patrol. PS had been observed earlier in the day with a severe hand injury which impacted his mobility, though no open wound was observed. PS separated himself from the group and moved a few meters to a patch of ferns where he began consuming the leaflets. The bout lasted approximately 3-minutes. No other group members were observed feeding on this species, and this was only the second case of fern ingestion reported in Budongo in over 30-years of observations (unpublished site data). Health states of individuals from the past event were unfortunately not recorded. Whether or not C . parasitica ’s highly anti-inflammatory properties were the principal motivator for the selection of this species remains unknown, however, regardless of intention, this plant may have benefitted PS by reducing pain and swelling in his injured hand.

Syzygium guineense.

S . guineense bark and leaves have both previously been found to exhibit a range of pharmacological activity, reviewed by Uddin et al. [ 109 ]. The antioxidant, analgesic, and anti-inflammatory activities of this plant have been attributed to flavonoids, tannins, saponins, carbohydrates, alkaloids, and cardiac glycosides in the extracts [ 109 – 112 ]. In our assays, S . guineense bark exhibited high antibacterial growth inhibition effects in vitro . The methanol-water bark extract (mwE098a) showed some level of inhibition against all bacteria tested in the dose-response assays, except for E . faecium and S . enterica . This was also the only extract, out of all tested, to inhibit growth of P . aeruginosa (IC 50 : 64 μg/mL; MIC: >256 μg/mL) a pathogen known to cause infections in the blood, lungs, and other body parts after surgeries [ 113 ], and was one of two extracts to reach a MIC value against S . maltophilia (IC 50 : 32μg/mL; MIC: 256 μg/mL). The other extract to reach a MIC value was the ethyl acetate S . guineense bark extract (eE098a; IC 50 : 64 μg/mL; MIC: 256 μg/mL). All bark and leaf extracts showed strong inhibition against E . coli (DSM 1576) in the dose-response assays, with the strongest results coming from the methanol-water extracts (mwE098a and mwE098b). All bark and leaf extracts of this species, except for the n -hexane bark extract (hE098a), inhibited E . cloacae , and were the only extracts in the study to do so. E . cloacae , while part of normal intestinal flora, can cause UTI’s and respiratory infections in humans [ 114 ]. S . guineense extracts were also the only extracts to inhibit A . baumannii at a concentration <256 μg/mL, with the methanol-water bark extract showing the strongest inhibition. A . baumannii can cause infections in wounds, blood, urinary tracts, and lungs [ 115 ]. The efficacy of methanolic extracts from this species suggests that the active compounds are polar molecules. In the anti-inflammatory COX-2 inhibition dose-response assays, only the n -hexane bark extract displayed strong inhibitory effects (IC 50 : 2.42 μg/mL), while the other extracts failed to exhibit significant activity during the pre-screening or ≥ 50% inhibition at 10 μg/mL. The COX-2 inhibition assays showed no inflammatory inhibition amongst leaf extracts at tested concentrations.

S . guineense can be found throughout Sub-Saharan Africa and is a common traditional medicine, for malaria [ 116 ]. The bark is also used for stomach aches, diarrhea, internal parasites, and infertility [ 68 , 109 ]. Ingestion of S . guineense bark is rare in Budongo, with no direct observations in either community throughout the study period, and only six total cases between 2008–2021 documented in the site’s long-term data. No observations of leaf ingestion of this species have ever been reported. The infrequent ingestion of S . guineense bark implies a more targeted use, making it unlikely to be a medicinal food. Instead, our pharmacological findings make this resource a strong candidate as a putative, therapeutic self-medicative resource. Unfortunately, as there is currently no health data associated with individuals who have recently consumed S . guineense bark, we do not yet know which properties chimpanzees may be targeting. However, based on pharmacological results, we recommend further investigation into this species as a curative agent for respiratory-related infections.

Scutia myrtina.

Kritheka et al. [ 117 ] in their study on the bioactivity of S . myrtina , found in vivo evidence that this species possesses dose-dependent anti-inflammatory, antimicrobial, and antifungal properties. Across our antibacterial assays, the bark sample of this species collected from the stem inhibited E . faecium (eE089a) and E . coli DSM 1576 (eE089a; mwE089a) in dose-response tests at concentrations ≤256 μg/mL. The refuse sample, collected from the ground below the plant’s stem, inhibited A . baumannii (hE089b), E . faecium (eE089b), and E . coli DSM 1576 (mwE089b; eE089b; hE089b) in dose-response tests below the specified concentration. Interestingly, the refuse sample inhibited more bacteria species overall than the fresh bark. The most potent antibacterial growth inhibition effects came from the ethyl acetate bark sample against E . faecium (eE089a; IC 50 : 64 μg/mL), though no MIC value was reached. In the COX-2 inhibition assays, the n- hexane bark extract had the fifth strongest inhibitory effect in vitro (hE089a; IC 50 : 1.19 μg/mL) out of all samples, while the ethyl acetate refuse bark sample was less potent, though still moderately active (E089b; IC 50 : 7.49 μg/mL).

As far as the authors know, this is the first published report presenting both behavioral and pharmacological evidence for S . myrtina bark as a putative medicinal resource amongst free-ranging chimpanzees (though see [ 118 ] for evidence based on food-combinations). Our behavioral observations indicate that an individual with a diverse and intense parasite infection deliberately sought out the bark of this species. The Budongo chimpanzees may, therefore, utilize S . myrtina as an anthelminthic. Across traditional accounts from multiple regions, S . myrtina is commonly used by people as an anthelminthic to treat intestinal worms [ 68 ], while aerial parts are also used to treat various bacterial infections. As we were not able to conduct urinalysis on the consumer during or after this event, we cannot determine whether the individual also harbored a bacterial infection at the time of ingestion. However, this possibility cannot be ruled out. Based on these findings, we propose S . myrtina be added to the list of putative chimpanzee self-medication behaviors as a treatment for internal parasites, and we encourage further exploration into the other specific chimpanzee health conditions that this species may help ameliorate.

Assessment of putative self-medicative behaviors

We synthesized pharmacological and behavioral evidence to assess therapeutic use of species associated with bark feeding, dead wood eating, and pith stripping behaviors. A summary of the antibacterial and anti-inflammatory results for each species is reported in S3 Table in S2 File . Overall, stem bark and dead wood samples were notable for their activity. Bark samples from every species showed >40% antibacterial inhibition against at least one bacterial strain. This activity was also true of the dead wood samples. When plant parts of the same species were tested ( S . guineense and F . exasperata ), barks generally exhibited more potent antibacterial and COX-2 inhibition activity than the leaves, likely to do with the higher concentration of plant secondary metabolites in bark. Our findings offer strong support that bark and dead wood eating of certain species could constitute novel self-medicative behaviors in wild chimpanzees. We also encourage more investigation into the bioactivity of non-bitter pith stripping, as the pith of A . polystachius showed strong antibacterial activity against E . faecium (hE099; IC 50 : 32 μg/mL; MIC: 128 μg/mL), and the piths of both A . polystachius and M . leucantha demonstrated significant anti-inflammatory properties at low concentrations. Future primatological research should prioritize the establishment of multi-disciplinary long-term projects that look systematically at health states of individuals who engage in bark, dead wood, and pith ingestion behaviors. We also encourage further pharmacological testing on other species used for these behaviors in Budongo and across primate field sites.

Drug discovery

Multidisciplinary studies on this topic have potential to lead to the discovery of new medicines which may benefit our own species [ 119 – 122 ]. Historically, PSMs have played a major role in the development of modern human medicine, and even today, a large portion of medicines are derived either directly or indirectly from plants and other natural materials [ 123 – 127 ]. Antimicrobial resistance is rising to dangerously high levels according to the World Health Organization [ 128 ] requiring the rapid creation of new antibacterial treatments. Infections caused by multi-drug resistant bacteria kill hundreds of thousands of people annually. Our findings of strong antibacterial growth inhibition across numerous plant species growing in Budongo have promising implications for our ability to discover novel compounds in existing forest habitats. Extracts should also be tested against additional bacteria and for anti-virulence effects, e.g., inhibition and disruption of biofilm formation, quorum sensing and toxin production, pursuing development of new therapeutic strategies that apply less evolutionary pressure, likely resulting in emergence of less antibiotic resistances in the future. Phytochemical characterization using advanced techniques, such as LC-ToF-MS and NMR, as well as potentially AI-assisted untargeted metabolomics approaches, are now needed to identify substances present in the most active extracts. This may eventually lead to the isolation and structure elucidation of yet unknown active ingredients and make way for determining their pharmacological selectivity and toxicity, while also taking potential synergistic effects into account.

Simultaneously, we are currently faced with a pressing need for more effective treatments to combat symptoms of acute inflammation and mediate long-term consequences of chronic inflammatory diseases [ 129 ]. The prostaglandin-producing cyclooxygenase-2 (COX-2) mediates and regulates pain, fever, wound inflammation, and many other medical disorders, as it plays a crucial role in the host organism’s defense against pathogens and injury. COX-2 inhibition has the same mechanism of action as non-steroidal anti-inflammatory drugs (NSAIDs). While inflammation is a normal part of the body’s defense against injury or infection, it can be damaging when occurring in healthy tissues or over a protracted period. Chronic inflammation can lead to cardiovascular diseases (CVD) and cancer, the two leading global causes of death [ 130 ]. Past studies have shown that the IC 50 values of Aspirin and ibuprofen (pure compounds and common NSAIDs) are 210 μg/mL and 46 μg/mL respectively for COX-2, and 5 μg/mL and 1 μg/mL respectively for COX-1 [ 131 , 132 ]. The in vitro COX-2/COX-1 selectivity ratio for Aspirin and ibuprofen is 42 and 46 respectively. Surprisingly, the 17 most active extracts in our COX-2 assays display lower IC 50 values than these popular NSAIDs, meaning our extracts have more potent inhibitory effects on the inhibition of COX-2 than the most common anti-fever and anti-pain drugs on the market. While COX-1 assays were beyond the scope of this study, future research should investigate COX-1 inhibition activity of these 17 extracts to calculate COX-2/COX-1 selectivity ratios. Doing so will allow for preliminary assessment of potential side effects, selectivity, and efficacy before future in vivo experiments can commence.

Future directions

Future research on this topic would benefit from the inclusion of control samples (plants or plant parts not consumed by chimpanzees); however, in this study, assay costs were a prohibiting factor. Additional information regarding the nutritional and mineral content of the species mentioned in this study is needed to better understand the motivations for ingestion. However, bioactivity and nutritional/mineral content are by no means mutually exclusive. It is, therefore, highly likely that these resources provide multiple benefits to consumers.

Future studies should also consider ecological variables. For example, different individual plants of the same species should be tested across habitat types to determine whether bioactivity varies based on location, age, life history, or time of harvest. Situating samples in their ecological context will provide a better understanding of whether chimpanzees select resources based on species alone, or other more nuanced criteria. Lastly, climatic studies in combination with pharmacological testing should examine how climate change may impact bioactivity of these plants, as shifting weather patterns have already been shown to alter nutritional content [ 133 ]. This information will be critical for establishing protected habitats that can sustain healthy, wild, primate populations.

Conclusions

As we learn more about the pharmacological properties of plants ingested by chimpanzees in the wild, we can expand our understanding of their health maintenance strategies. Our results provide pharmacological evidence, from in vitro assays of plant parts consumed by wild chimpanzees collected in situ , for the presence of potent bioactive secondary plant metabolites in Budongo chimpanzee diets for a variety of potential illnesses previously not considered. Whether these resources are consumed intentionally as a form of therapeutic self-medication or passively as medicinal foods, must be assessed on a case-by-case basis, taking behavioral observations into account.

For the field of zoopharmacognosy to progress, we encourage continued multidisciplinary collaboration between primatologists, ethnopharmacologists, parasitologists, ecologists, and botanists [ 9 ]. Beyond improving our broad understanding of chimpanzee health maintenance, multidisciplinary studies will benefit our own species, potentially leading to the discovery of novel human medicines to combat the looming problem of growing drug-resistance. For this to happen, however, it is imperative that we urgently prioritize the preservation of our wild forest pharmacies as well as our primate cousins who inhabit them.

Materials availability

Voucher specimens for each species were deposited at the Makerere University Herbarium in Kampala, Uganda for taxonomic identification and storage. A duplicate set was deposited at the University of Oxford Herbarium for permanent storage.

Supporting information

S1 fig. budongo chimpanzees consuming resources tested in this study..

a.) IN eating K . anthotheca bark and resin b.) MZ eating S . myrtina bark c.) KC stripping A . polystachyus pith d.) MB eating C . patens dead wood e.) OZ eating S . guineense bark (post-study period) g.) MZ eating F . exasperata bark.

https://doi.org/10.1371/journal.pone.0305219.s001

S2 Fig. Generalized multi-method workflow used in this study.

https://doi.org/10.1371/journal.pone.0305219.s002

S3 Fig. Voucher samples collected in duplicate.

a . ) C . alexandri (00243133G) b . ) A . polystachius (00243136J) c . ) W . elongata (00243129L) d . ) C . parasitica (00243122E) e . ) K . anthotheca (00243123F) f . ) F . variifolia (51195) g . ) M . leucantha (51203) h . ) A . boonei (51204) i . ) D . dewevrei (00243132F) j . ) S . guineense (00243135I) k . ) S . myrtina (00243128K) l . ) F . exasperata (00243130D).

https://doi.org/10.1371/journal.pone.0305219.s003

S4 Fig. Plate layouts for growth inhibition assays.

[Top] Library Screen: done in 96-wells-mikrotiterplate; AB: Antibiotic as positive control; DMSO: vehicle control / negative control; GC: growth control: containing working culture, to check whether the bacterium grew/active; [Bottom] Dose-Response: done in descending concentration of samples, DMSO, and antibiotic. MB: Media blank, consisted of CAMHB as negative/ sterile media control; DMSO as negative/ vehicle control; GC: growth control, consisted of working culture.

https://doi.org/10.1371/journal.pone.0305219.s004

S5 Fig. ELISA assay setup for anti-inflammatory assay.

https://doi.org/10.1371/journal.pone.0305219.s005

S1 File. Supplementary materials: Methods .

https://doi.org/10.1371/journal.pone.0305219.s006

S2 File. Supplementary tables.

https://doi.org/10.1371/journal.pone.0305219.s007

Acknowledgments

We are grateful to all the field staff working in Budongo who provided invaluable instruction and guidance, generously sharing both scientific insight and traditional knowledge. This study could not have been done without their contributions. Specifically, we would like to thank members of the Perspectives Collective: Chandia Bosco, Monday Mbotella Gideon, Adue Sam, Asua Jackson, Steven Mugisha, Atayo Gideon, and Kizza Vincent, and Walter Akankwasa, as well as site director David Eryenyu. We would also like to thank Godwin Anywar for his assistance with plant identification at the Makerere Herbarium, Stephen Harris at the University of Oxford’s Herbarium for his facilitation of voucher storage, and the Natural History Museum in London for their aid in parasite identification. We are grateful to Vernon Reynolds who founded the field site and to the Royal Zoological Society of Scotland for providing core support. We also gratefully acknowledge the Uganda Wildlife Authority and the Uganda National Council for Science and Technology for granting permission to conduct research in Uganda. Lastly, thank you to the staff and students at Neubrandenburg University of Applied Sciences who made this collaboration possible, and to research assistant, Finn Freymann, for his help with botanical extractions.

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