How do you structure a research paper introduction?

Use the funnel: start broad and narrow to your study. The CARS model names three moves — establish the territory (why the topic matters, what is known), establish the niche (the gap or problem in that knowledge), and occupy the niche (your aim, question, or hypothesis, and briefly how you address it). It moves from the general field to your specific contribution.

What should the first sentence of an introduction do?

It should establish why the topic matters to your field, in plain, specific terms — not with a dictionary definition or a sweeping claim like 'Since the dawn of time'. Anchor it in the real significance or scale of the problem, ideally with a citation, so the reader immediately sees the stakes.

Where does the research gap go in an introduction?

The gap is the hinge of the introduction. After you establish what is known, you state what is missing, unresolved, or contradictory — and that gap directly motivates your aim, which comes next. The aim should read as the natural answer to the gap you just identified.

How long should a research paper introduction be?

For a journal article, usually a few paragraphs — roughly 10 to 15 percent of the paper. It should be long enough to establish the territory, the gap, and the aim, but no longer; the detailed literature belongs in the literature review or is woven in concisely, not exhaustively reviewed here.

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How to write a research paper introduction

By Dr. Rafiq Muhammad, MD, PhD · Updated June 2026

A good introduction is a funnel: it starts broad — why this topic matters — and narrows to one specific thing, your study. The classic recipe is the CARS model: establish the territory, establish the niche (the gap), then occupy it with your aim. Get those three moves in order and the reader arrives at your question feeling it was inevitable.

The three moves (CARS)

Establish the territory — why the topic matters and what’s already known. Anchor the stakes (scale, significance), ideally with a citation.
Establish the niche — the gap: what’s missing, unresolved, or contradictory in that knowledge.
Occupy the niche — your aim, question, or hypothesis, and a sentence on how you address it.

The hinge is the gap. Everything before it sets up a problem; everything after it is your answer. If a reader can’t point to the sentence where “what’s known” turns into “what’s missing,” the introduction hasn’t done its job.

The first sentence

Open with why the topic matters to your field — concretely. Avoid the dictionary definition and the cosmic opener (“Since the dawn of time…”). A specific fact about the scale or cost of the problem, cited, earns attention in a way a broad generalisation never does.

What to keep out

An exhaustive literature review — that’s the literature review’s job; here you cite selectively to build the gap.
Results or conclusions — the introduction poses the question; it doesn’t answer it.
Definitions of common terms, and throat-clearing (“In this paper, I will…” can usually be tightened).

How long?

For a journal article, a few paragraphs — roughly 10–15% of the paper. Long enough for territory, gap, and aim; no longer. It’s the top of the IMRaD structure, mirrored at the end by a discussion that returns to the same gap and shows you filled it.

Not sure your aim actually answers the gap you set up? The free Research Question Validator pressure-tests the question your whole introduction funnels toward.

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Section-by-section templates, an introduction funnel worksheet, and worked examples from Write and Publish a Scientific Paper. We’ll email you the download link.

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Frequently asked questions

How do you structure an introduction?

The funnel / CARS model: establish the territory, establish the niche (the gap), then occupy it with your aim.

What should the first sentence do?

Show why the topic matters — concretely, ideally cited. Skip dictionary definitions and cosmic openers.

Where does the gap go?

It’s the hinge — after what’s known, before your aim. Your aim should answer the gap directly.

How long should it be?

A few paragraphs — roughly 10–15% of the paper. Territory, gap, aim; no exhaustive review.

IMRaD structure → How to write a conclusion →