How to Write a Research Paper Introduction

The introduction to a research paper does more than introduce the topic. It makes the case that the study needed to exist. A reader who finishes the introduction should understand: what problem the study addresses, why that problem matters, what is already known about it and why existing knowledge is insufficient, and what this specific study contributes.

This guide covers the structure, the components, annotated examples, and the mistakes that make introductions weak.

The Three-Move Structure

Linguist John Swales (1990) studied hundreds of research paper introductions and identified three rhetorical moves that successful introductions make, in this order:

Every element of the introduction can be mapped onto one of these three moves. When an introduction feels weak or unfocused, it is usually because one of the three moves is missing or underdeveloped.

Components of a Research Paper Introduction

Within the three-move structure, a complete introduction typically includes the following elements in roughly this order:

Hook: An opening that establishes why the topic matters, using a striking statistic, a problem statement, or a paradox. Not a rhetorical question and not "Since the dawn of time..."

Background: The essential context a reader needs to understand the problem. This is not a literature review; it is the minimum background required to understand the research gap.

Literature context: What is already known about this topic and what the existing research has established.

Gap statement: The specific thing that existing research has not adequately addressed. This is the justification for the study.

Thesis or research purpose: What this study does, argues, or investigates.

Roadmap (optional): A brief statement of the paper's structure, common in longer papers and dissertations.

Annotated Example 1: Social Sciences

Research question: Does passive social media use predict depressive symptoms in adolescents?

[HOOK: Establishes why the topic matters]

Rates of persistent sadness and hopelessness among US high school students increased from 26 percent in 2009 to 44 percent in 2023 (CDC, 2024). Over the same period, the share of adolescents who own smartphones rose from 23 percent to 95 percent (Pew Research Center, 2023). Whether these concurrent trends are causally related is one of the most contested questions in adolescent health research.

[LITERATURE CONTEXT: What is known]

A substantial body of research links social media use to negative mental health outcomes in adolescents. Cross-sectional studies consistently find associations between heavy social media use and depressive symptoms (Twenge et al., 2018; Kelly et al., 2019). A meta-analysis of 13 longitudinal studies found a small but statistically reliable prospective association between social media use and depression (Coyne et al., 2020). At the same time, experimental studies that randomly reduced social media use have produced mixed results (Hunt et al., 2018; Tromholt, 2016), and Orben and Przybylski (2019) showed that the overall effect size is modest.

[GAP: What existing research has not addressed]

A critical limitation of this literature is that virtually all studies treat social media use as a single, undifferentiated variable. There is strong theoretical and empirical reason to believe that passive use (scrolling without interacting) and active use (posting, commenting, messaging) have distinct psychological effects. Fardouly and Vartanian (2015) found that passive consumption predicted social comparison while active engagement did not, yet no longitudinal study has directly tested whether passive and active use differentially predict depressive symptom onset in a clinical-instrument-based sample.

[THESIS/PURPOSE: What this study does]

The current study addresses this gap by examining 24 months of passive-device-monitoring data on social media activity alongside quarterly PHQ-9 assessments in a prospective sample of 312 adolescents aged 12 to 16. We test the hypothesis that passive social media use predicts increases in depressive symptoms while active use does not.

[ROADMAP]

We begin with a review of theoretical and empirical evidence distinguishing passive from active use, then describe the study's design and methods, present fixed-effects regression results, and conclude with implications for both research and intervention design.

Annotated Example 2: Humanities

Research question: How do Victorian conduct manuals construct femininity as a form of social control?

[HOOK]

Between 1830 and 1900, over four hundred conduct manuals for women were published in Britain, advising on everything from posture and speech to emotional expression and moral comportment. These texts were among the most widely read of the Victorian period, outselling many novels.

[BACKGROUND AND LITERATURE CONTEXT]

Scholars of Victorian gender have long recognized the conduct manual as a site of ideological production. Armstrong's (1987) foundational work demonstrates that domestic fiction and conduct writing together constructed a specifically feminine form of subjectivity defined by interiority, self-regulation, and moral influence over men. Poovey (1988) shows how the figure of the "proper lady" was produced through contradictory discourses that simultaneously idealized and constrained women. More recent work by Mitchell (2004) and Ablow (2010) has examined specific genres of Victorian women's writing for the traces of this ideological formation.

[GAP]

What remains underexamined is the textual mechanics by which conduct manuals produced their effects: specifically, how they addressed readers so as to produce a self that experienced its own constraint as freedom. Previous scholarship tends to read conduct manuals as straightforward instruments of patriarchal ideology without attending to the ways these texts negotiated resistance, ambivalence, and the active pleasures they offered female readers.

[THESIS]

This essay argues that conduct manuals of the 1840s to 1870s relied on a rhetorical strategy of internalization: they invited readers to identify with an idealized self who freely chose the behaviors being prescribed, thereby transforming external social pressure into apparent self-determination. Reading three widely circulated texts by Sarah Ellis alongside their known reception histories, I show that this strategy was not wholly successful: the texts bear consistent marks of the resistance they attempted to preempt.

Common Mistakes

The funnel that never narrows. Starting with broad statements about the topic, becoming gradually more specific, but never arriving at a clear gap or thesis. Every sentence that does not advance toward the thesis is a sentence the reader is waiting to get past.

Excessive literature summary. The introduction is not the literature review. Its job is to establish the gap, not to survey the field. Save detailed source-by-source review for the literature review section or chapter.

A vague gap statement. "More research is needed" or "this has not been studied enough" is not a gap statement. A gap statement identifies the specific type of evidence that is missing, the specific population or context that has not been studied, or the specific methodological problem with existing work.

Announcing the findings in the introduction. "This study finds that X leads to Y." The introduction should state the research question and the approach, not preview the results. Results belong in the results section.

Starting with a dictionary definition. Opening with "According to Merriam-Webster, [concept] is defined as..." is considered weak academic writing. Definitions belong in conceptual or methods sections, not introductions.

Too long. For a journal article, the introduction is typically 400 to 800 words. For a thesis chapter, 600 to 1,200 words. Introductions that run to 2,000 words without a dedicated literature review section are usually replacing that section rather than introducing it.

Introduction Length by Paper Type

Writing the Introduction Last

Many experienced researchers write the introduction after the other sections are complete. The introduction argues for the importance of what you found. You cannot make that argument before you know what you found.

The common workflow: write the methods and results first, write the discussion while analyzing results, then write the introduction once you know exactly what the contribution is. The abstract is last.

Frequently Asked Questions

How do you start a research paper introduction? Start with a hook that establishes why the topic matters: a striking statistic, a documented trend, a well-characterized problem, or a tension in the existing literature. Avoid opening with a rhetorical question ("Have you ever wondered...") or a broad generalization ("Since the beginning of time..."). The first sentence should place the reader immediately in the problem space.

What are the 5 parts of a research introduction? A complete research paper introduction includes: (1) a hook or opening that establishes significance, (2) background context, (3) a review of what the existing literature establishes, (4) a gap statement identifying what existing research has not addressed, and (5) the thesis or purpose statement explaining what this study contributes. Longer papers also include a brief roadmap.

How long should a research paper introduction be? For a journal article, 400 to 800 words. For an undergraduate paper, 150 to 300 words. For a dissertation, 800 to 1,500 words for the introduction to the full document. The introduction should be proportional to the paper's length; a 2,000-word essay does not need an 800-word introduction.

What should not be in a research paper introduction? The introduction should not include: detailed methods (that goes in the methods section), results or findings, extensive source-by-source literature summaries (that goes in the literature review), dictionary definitions as opening moves, or personal background on how you became interested in the topic.

Should you write the introduction first or last? Many experienced researchers write the introduction last, or at least revise it last. The introduction argues for the importance of your contribution. It is easier to make that argument once you know precisely what you found and how it differs from prior work.

For related academic writing guidance, see how to write an abstract, thesis statement examples, literature review example, and how to write a literature review.