How to Write a Research Paper Introduction

A research paper introduction makes three moves, from general to specific: it shows that the topic matters and what is already known, it points to what is still missing, and it says what this study does about it. John Swales named these moves in his CARS model. This guide shows how to write a research paper introduction with them, step by step, and annotates two published introductions sentence by sentence.

Key Takeaways

• Answer three questions in order: what is known, what is missing, and what this study does. Swales calls them establishing a territory, establishing a niche and occupying the niche.
• Give the gap its own sentence, with a signal word such as “few”, “little”, “lack” or “unclear”.
• End on the aim, question or hypothesis, in no more than two sentences, and make it answer the gap; a line on how the paper is organized can follow.
• Biomedical guidance puts an introduction at about 250 to 300 words; the education paper below runs close to 2,700 words before its method. Check your journal or assignment.
• Draft the aim early, but write the full introduction after the method and results.
• A dissertation Chapter 1 adds a problem statement, significance, limitations and definitions, and leaves the full literature review to Chapter 2.

What goes in a research paper introduction?

A research paper introduction holds the background a reader needs, a short account of the studies that matter most, the gap those studies leave, and the aim, question or hypothesis of your study. In many fields it ends with a line on how the paper is organized. The order runs from broad to narrow, which is why writing guides draw it as a funnel or an inverted triangle.

Swales described the pattern in Genre Analysis (1990), from his analysis of published research articles, and called it CARS, for Create a Research Space. The steps in the table below follow the USC Libraries guide to the model; the signal phrases come from that guide and from the two introductions annotated later.

In both examples below, Move 1 takes most of the words and Move 2 a single sentence. In an IMRaD paper the introduction is the first of four sections, as the template in our research paper outline shows. The glossary entry on the introduction covers the essay version, which follows different rules.

How do you write a research paper introduction, step by step?

Work backwards. Write the aim sentence first, gather the few studies that lead to it, name the gap they leave, and only then write the opening paragraph that sets up the topic. Revise the whole section once the paper is finished. Starting from the aim keeps every sentence pointed at it, so the introduction never drifts into a general essay on the topic.

1. Write the aim in one or two sentences. Bahadoran and colleagues, reviewing guidance on biomedical introductions, say the objectives should “preferably comprise no more than two sentences”. Name the population, the variables or phenomenon, and the kind of answer you want.
2. Choose the handful of studies that lead to it. USC’s guide says the introduction “should not represent a comprehensive literature review”; the review comes next. Keep the studies that show the topic matters and those closest to your question.
3. Write the gap sentence. Say what those studies have not done: a population nobody has tested, two variables nobody has linked, findings that disagree. Use a signal word from USC’s list (“few”, “little”, “lack”, “unclear”, “inconclusive”) or the neutral wording USC also gives, “Prior research has focused primarily on A, rather than on B”. The glossary entry on the research gap lists the usual kinds.
4. Open with the topic. USC suggests using key words from your title in the first few sentences, and Bahadoran and colleagues warn against sweeping generalizations in the opening sentence.
5. Order the paragraphs as a funnel. One idea per paragraph: what is known in general, what is known about your population, then the gap. A common tense pattern, per Bahadoran and colleagues: present simple for background, present perfect for what research has shown over time, present simple again for your aim.
6. Close on the question or hypothesis. If you predict an outcome, give the reason; UNC’s Writing Center asks students to justify a hypothesis, not only state it. If your field expects it, add one line on how the paper is organized.
7. Check it against the finished paper. Bahadoran and colleagues list inconsistency with other sections, and overlap with the discussion, among the common pitfalls.

Research paper introduction example 1: a health study

Dudo and colleagues (2022) surveyed medical students in Germany about sleep and depressive symptoms. BMC Research Notes publishes short papers, and this introduction is three paragraphs and 364 words, reprinted in full under the article’s Creative Commons Attribution 4.0 licence (the bracketed numbers are the paper’s citations).

Mental health is defined by the World Health Organization (WHO) as the “state of well-being in which an individual realizes his or her own abilities, can cope with the normal stresses of life, can work productively and is able to make a contribution to his or her community” [1]. It therefore forms a prerequisite for a stable and successful professional life in the medical field. Doctors often face emotionally stressful situations in their everyday work and carry a great responsibility for their patients. They are expected to act professionally, competently, and sensitively and to always be able to justify their actions. It is not uncommon for high levels of self-expectations and the demanding work environment to impact the mental health of physicians. [2]. Trainee doctors often face emotionally stressful situations early on in their medical degree programs. Numerous studies describe these challenges and the physical and mental health of medical students [3, 4]. In addition to anxiety disorders and behavioral disorders, depression is one manifestation of declining mental health [1]. In recent years, the large number of cases of depression among medical students has received more attention [5].

Sleep is crucial for the physical and mental regeneration of the body and therefore of great importance to mental health. A recent meta-analysis revealed that sleep quality is particularly poor amongst medical students, the highest prevalence of this phenomenon having been seen in students in Europe and America [6]. Poor sleep quality correlates to reduced academic performance [7] and is associated with the onset of anxiety, depression, and stress. A long sleep latency time (the time it takes an individual to fall asleep) may be an indicator of depression [8]. Also, reduced sleep duration has a negative effect on academic performance [9] and is more frequently associated with burnout [10].

To date, there have been very few studies involving medical students that examine the association between single sleep characteristics and the outcome of the Beck Depression Inventory-II (BDI-II). Therefore, the aim of the present study is to explore the possible association of sleep characteristics with depressive symptoms. The findings of this study will help to establish targeted interventions to improve the mental health of medical students.

Here it is again, sentence by sentence (17 sentences in all).

What works. Move 1 builds two strands, depression in medical students and sleep in medical students, and the gap sentence is the first place they meet. That is the shape to copy: each strand of background ends up inside the gap sentence. The aim also matches the design: a cross-sectional survey supports an association, so the authors write “explore the possible association” and make no causal claim. There are no results and no outline of the paper, which suits a short-report journal.

What we would tighten. The real subject, medical students, first appears in sentence 6; starting there would save five sentences. The gap sentence has no citation, so readers take “very few studies” on trust. And “sleep characteristics” is vaguer than the method, which used the Pittsburgh Sleep Quality Index. A sharper aim, in our wording: “to test whether sleep quality, sleep latency, sleep duration and use of sleeping pills are associated with depressive symptoms on the BDI-II.” The gap and aim sentences also reappear, almost unchanged, in the paper’s abstract; our abstract examples show what else an abstract needs.

Research paper introduction example 2: an education study

Ranellucci (2025) asked university students about their most severe academic regret, in two studies published in Frontiers in Psychology under a CC BY licence. The 213-word paragraph under the paper’s Introduction heading makes all three moves on its own; it is reprinted in full.

Experiencing some type of regret is an inevitable part of life. People may regret occupational choices such as becoming a professor, health related decisions such as drinking too much alcohol, or academic choices such as not choosing to do a bachelor’s in computer science. Although regrets are an unpleasant emotional experience, they can help us reflect on past mistakes and shape future choices and behaviors. Reflecting on one’s regrets can initiate corrective measures such as a change in career, healthier diet, or enrolment in a new academic program. As such, experiencing regrets can have an important function in the growth and development of healthy and happy individuals. Surprisingly, despite consistent evidence suggesting that the most common life regrets relate to education (Roese and Summerville, 2005) and a recent increase in research on emotions in education (Pekrun and Linnenbrink-Garcia, 2014), little work has investigated the relevance of regrets in educational contexts. Focusing on regrets can extend popular educational theories (e.g., affective memories within situated expectancy-value theory; Eccles and Wigfield, 2020) and can guide practice (e.g., past and anticipated regrets can help students make informed academic choices). Consequently, this paper identifies and ranks the categories of regrets that college students report, examines characteristics of these regrets, and explores relations with relevant motivational and emotional outcomes.

What works. Two of the paragraph’s three citations sit in the gap sentence, chosen to make the gap surprising: most life regrets are about education, and emotions in education are a growing field, yet regrets in education are little studied. The aim sentence has three parts (identifies and ranks, examines, explores), and each becomes one research question.

The paragraph is only the opening. Four more headed sections, about 2,450 words, follow before the first method section: what regret is, regret in education, the theory, and the current study. The last returns to Move 3 in detail:

RQ 1: What are the salient academic regrets reported by college students?

RQ 2: How do salient academic regrets differ in terms of intensity, intrusive thoughts, and ratings of omission (i.e., something not done) or commission (i.e., something done)?

RQ 3: How do regret intensity, intrusive thoughts, and ratings of regrets as an omission or commission relate to achievement goals, expectancy, value, costs, and emotions?

For RQ 2 the author writes that “no specific predictions are proposed”, since earlier research is too thin to predict from; for RQ 3, theory supports “some tentative predictions”, stated as hypotheses. That is the honest rule: ask a question where you cannot predict, and state a hypothesis where earlier work gives you a reason. Our research question examples show how wording follows design, and our hypothesis examples show published predictions with their reasons.

How long should a research paper introduction be?

There is no single length. For biomedical papers, Bahadoran and colleagues report that about 250 to 300 words is usually enough, sometimes 500 to 600, in two or three paragraphs and sometimes four. They also report a recommended ceiling of 10% to 15% of the manuscript, excluding the abstract and references. Length depends on the field, the journal and the type of paper.

Our two examples sit far apart: 364 words for the health paper, close to 2,700 before the method in the education paper. Bahadoran and colleagues add two warning signs: an introduction more than two-thirds the length of the results section is probably too long, and a long one is sometimes used to make up for thin data, which reviewers notice.

When should you write the introduction?

Write the full introduction late, after the method and results, and revise it last. You only know what the paper delivers once those sections exist. Draft the aim early, though, because the aim decides which studies belong in the introduction. Guides from UNC, USC and George Washington University all point the same way.

UNC’s Writing Center notes that “many writers find that composing their Methods and Results before the other sections helps to clarify their idea of the experiment or study as a whole.” USC’s guide recommends reviewing the introduction late, “because outcomes are unknown until you’ve completed the study.” George Washington University’s dissertation guide says that in some programs Chapter 1 is written after Chapters 2 and 3, because parts of it summarize them.

What are the most common mistakes in a research paper introduction?

Most weak introductions fail in one of two ways: they never get to the point, or they get there without a reason. The first shows up as a broad opening and a long survey of studies; the second as a missing gap or a vague aim. The table draws on the eight pitfalls Bahadoran and colleagues list and on the CARS moves.

Fields disagree on the last row. The CARS model includes announcing the principal findings as a step in Move 3, while Bahadoran and colleagues count presenting the conclusion as a pitfall “except for studies where the format requires this”. In a student IMRaD paper, stop at the question. To see where background ends and a review begins, compare our literature review example.

How is a thesis or dissertation introduction different?

A thesis or dissertation introduction is a whole chapter, not a few paragraphs. It still makes Swales’s three moves, spread across headed sections: the problem, the purpose and research questions, why the study matters, and how it was done. The detailed literature review moves to Chapter 2, and Chapter 1 only summarizes it.

The University of Maryland Eastern Shore’s graduate writing center tells thesis writers that in Chapter 1 “You are essentially employing a CARS approach”. George Washington University’s Graduate School of Education and Human Development lists the sections its Chapter 1 should contain, in this order.

Three practical differences follow. The problem must be a real one: in the GWU guide’s example, a favorite reading program being rarely used “does not constitute a problem; widespread impaired reading in inner-city elementary schools is a problem.” The research questions must match the methods chapter word for word. And USC’s guide says every introduction should end on how the rest of the work is organized, which in a thesis means an outline of the chapters. Your graduate school’s handbook overrides all of this.

Where Papero fits

Papero is an AI writing workspace for students and researchers. When you start a paper, its outline builder can use a standard IMRaD template, and the Introduction heading comes with one prompt in three points: “The problem and why it matters”, “What is already known, and the gap” and “Your research question or aim”. Together they follow Swales’s three moves, in order.

Find papers searches more than 250 million papers through OpenAlex, which helps with the handful of studies Move 1 needs, and the Claims check in Review finds sentences that need a citation. The research paper writing page shows the steps from outline to Word export. You can sign up free. Deciding what the gap is, and how to word your question, stays your job.

Frequently Asked Questions

What are the 5 elements of a good introduction?

For a research paper: the topic and why it matters, what earlier studies found, the gap they leave, the aim, question or hypothesis, and, in many fields, a short note on how the paper is organized. The first four follow John Swales’s CARS model; the fifth depends on the journal or assignment.

What is the CARS model?

CARS stands for Create a Research Space, a model John Swales published in Genre Analysis (1990) from his analysis of research articles. It describes three moves: establishing a territory (the topic and what is known), establishing a niche (the gap), and occupying the niche (what the present study does). Writing guides use it as a template for research introductions and thesis first chapters.

Should a research paper introduction include results?

Usually not in a student paper. A 2018 review of biomedical writing guidance reports that several guides advise against results in the introduction, and lists presenting the conclusion there as a common pitfall unless the journal’s format requires it. Some journal formats do expect the main findings there, so check the author guidelines.

What is the difference between an introduction and a literature review?

An introduction cites a handful of studies to show what is known and where the gap is, then states the aim. A literature review evaluates the research on a topic in detail, grouping and comparing studies. In a journal article a short review sits inside the introduction; in a thesis it is usually a separate chapter.

Sources

• Bahadoran, Z., Jeddi, S., Mirmiran, P., & Ghasemi, A. (2018). The principles of biomedical scientific writing: Introduction. International Journal of Endocrinology and Metabolism, 16(4), Article e84795. https://doi.org/10.5812/ijem.84795
• Dudo, K., Ehring, E., Fuchs, S., Herget, S., Watzke, S., Unverzagt, S., & Frese, T. (2022). The association of sleep patterns and depressive symptoms in medical students: A cross-sectional study. BMC Research Notes, 15, Article 109. Licence: CC BY 4.0. https://doi.org/10.1186/s13104-022-05975-8
• Endicott, K. (n.d.). Writing the introduction of your thesis/dissertation [Workshop slides]. Graduate Writing Center, University of Maryland Eastern Shore. https://wwwcp.umes.edu/grad/wp-content/uploads/sites/120/2023/10/GWC-Workshop-Writing-the-Introduction-Chapter.pdf
• George Washington University, Graduate School of Education and Human Development. (2022). Dissertation content and style guide. https://gsehd.gwu.edu/sites/g/files/zaxdzs4166/files/2022-06/diss_styleguide_2022.pdf
• Ranellucci, J. (2025). Investigating the content and correlates of undergraduate students’ academic regrets. Frontiers in Psychology, 16, Article 1436323. Licence: CC BY. https://doi.org/10.3389/fpsyg.2025.1436323
• Swales, J. M. (1990). Genre analysis: English in academic and research settings. Cambridge University Press.
• University of North Carolina at Chapel Hill, The Writing Center. (n.d.). Scientific reports. https://writingcenter.unc.edu/tips-and-tools/scientific-reports/
• University of Southern California Libraries. (n.d.). 4. The introduction. In Organizing your social sciences research paper. https://libguides.usc.edu/writingguide/introduction
• University of Southern California Libraries. (n.d.). The C.A.R.S. model. In Organizing your social sciences research paper. https://libguides.usc.edu/writingguide/CARS