How to Write the Introduction of a Research Paper: Funnel Structure, Gap Statement and Aim (with Examples)

A four-layer funnel from context to aim, gap statement templates, aim formulas by study design and a worked four-paragraph example.

Written by
Dr. CharlieSenior Medical Writer
Published
Reading time
6 minutes
Sources
7 cited
  • Original research article
  • Manuscript writing
  • Introduction
Research paper introduction
Length
4–5 paragraphs, ~10–15% of words
Structure
Context → evidence → gap → aim
Ends with
One testable primary aim
Guidelines
ICMJE, CONSORT 2025, STROBE
On this page
  1. Quick answer
  2. Overview
  3. What the introduction of a research paper must do
  4. Funnel structure: four layers from broad context to specific aim
  5. How to write a gap statement (with templates)
  6. How to write the research aim, objectives and hypothesis
  7. Worked example: a four-paragraph introduction (illustrative)
  8. Common mistakes in the introduction of a research paper
  9. Pre-submission checklist for the introduction
  10. Writing the introduction for an international journal as an author in Germany
  11. Questions
  12. References
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Quick answer

  • To write the introduction of a research paper, move through four layers: broad context, what is already known, the research gap and why it matters, and the research aim, hypothesis and design.
  • End with one testable aim that matches the abstract and the Methods section of your manuscript.

01Overview

The research paper introduction has one job: to persuade editors, reviewers and readers that your question is important, still unanswered and answerable by the study you ran. It also has a defined length: typically four to five paragraphs and no more than about 10–15% of the total word count [1]. This guide shows the funnel structure, how to write a gap statement and how to finish with a precise research aim, with a worked example and a checklist.

02What the introduction of a research paper must do

After the last paragraph, readers should be able to answer three questions: What is known? What is not known, and why does it matter? What did the authors do about it? The ICMJE recommends that the introduction give the context or background for the study and state its specific purpose, objective or hypothesis [2]. Anything that does not serve those answers belongs in the Discussion or should be cut.

Plan before you draft. Cals and Kotz suggest working from a skeleton of the paper, picking out the lead sentence of each paragraph and then developing them into the text [1, 3].

03Funnel structure: four layers from broad context to specific aim

The funnel mirrors the three “moves” of Swales’ CARS model (Genre Analysis, 1990): establishing a territory, establishing a niche and occupying the niche. In practice it becomes four layers.

Table 1. The funnel structure: four layers from broad context to specific aim
Funnel layerPurposeTypical lengthExample opener
1. Broad contextShow why the topic matters (burden, clinical or policy relevance).2–3 sentences“[Condition] is a frequent cause of…”
2. What is knownSummarise the most relevant, recent and highest-quality evidence.1–2 paragraphs“Previous studies have shown…”
3. Gap statementShow what is missing or contradictory and the consequence of not knowing.1 paragraph“However, it remains unclear whether…”
4. Aim and designState the research aim, hypothesis and study design.1–2 sentences“Therefore, we aimed to…”

Layers 1 and 2 set the rationale. Lead with systematic reviews, guidelines and large primary studies rather than a long literature review; give every factual claim a citation; and keep the focus on the population, exposure and outcome you studied. The Declaration of Helsinki expects medical research to rest on a thorough knowledge of the scientific literature [4].

04How to write a gap statement (with templates)

A gap statement turns the preceding evidence into a problem statement. A practical three-part formula: (1) what is known, (2) what is unknown, conflicting or limited, and (3) why that matters for patients, practice or policy.

Common types of research gap (a practical grouping; published taxonomies use six or seven categories):

  • Knowledge gap: the question has not been studied.
  • Population gap: results exist only for other age groups, sexes or genders, or risk profiles.
  • Methodological gap: earlier studies were small, retrospective or used inconsistent outcomes.
  • Context gap: findings may not transfer to your health system or care setting.
  • Evidence conflict: published studies disagree and the reason is unexplained.
Table 2. Weak versus strong gap statements
WeakStrong
“Few studies have examined this topic.”“Evidence comes mainly from single-centre trials in younger adults, so it is unclear whether the effect holds in people over 75 treated in routine care.”
“Nobody has studied this in Germany.”“Outcomes under German referral and reimbursement pathways have not been reported, which limits the transfer of international findings to local practice.”
“We are the first to study this.”“To our knowledge, and after a structured literature search, no study has compared X with Y on outcome Z.”

Run a structured search before you claim novelty; “first study” statements are a common target during peer review.

05How to write the research aim, objectives and hypothesis

End with one primary study aim, written with the elements of PICO (population, intervention or exposure, comparator, outcome) and the design. The major reporting guidelines agree: CONSORT asks for the scientific background and rationale and for specific objectives [5], and STROBE asks for stated objectives, including any prespecified hypotheses [6].

Table 3. Aim formulas by study type
Study typeAim formula
Randomised trialWe aimed to compare the effect of [intervention] versus [comparator] on [primary outcome] in [population].
Cohort studyWe aimed to investigate whether [exposure] is associated with [outcome] in [population] over [follow-up].
Cross-sectional studyWe aimed to estimate the prevalence of [condition] and its association with [factors] in [setting].

If sex or gender differences are plausible, say so in this final layer; the SAGER guidelines ask authors to report whether such differences may be expected [7] (see our SAGER guidelines guide).

06Worked example: a four-paragraph introduction (illustrative)

Table 4. Worked example: a four-paragraph introduction (illustrative; replace each statement with verified, cited facts)
LayerExample text
Paragraph 1: contextHip fracture is a common reason for hospital admission in older adults and is often followed by loss of independence. Early mobilisation after surgery is widely recommended in care pathways.
Paragraph 2: evidenceRandomised and observational studies suggest that mobilisation within 24 hours is associated with a shorter hospital stay, although the definition of “early” and the intensity of mobilisation differ between studies.
Paragraph 3: gapHowever, most evidence comes from single-centre studies, and it remains unclear whether early mobilisation improves walking ability at three months in patients with cognitive impairment. This matters because these patients are often excluded from trials yet form a large share of ward populations.
Paragraph 4: aimWe therefore conducted a multicentre prospective cohort study to compare walking ability at three months between patients mobilised within 24 hours and later, stratified by cognitive status. We hypothesised that early mobilisation would be associated with better walking ability in both strata.

07Common mistakes in the introduction of a research paper

  • Starting too broadly and taking three paragraphs to reach the topic.
  • Writing a full literature review instead of a focused funnel.
  • Hiding or omitting the gap, so the aim appears unmotivated.
  • Stating an aim that differs from the abstract, Methods or trial registration.
  • Reporting results or conclusions in the introduction.
  • Claiming novelty without a systematic search, or leaving claims uncited.

08Pre-submission checklist for the introduction

  • The text follows the funnel: context → evidence → gap → aim.
  • Length is about four to five paragraphs, within roughly 10–15% of the word count and the journal’s limits.
  • The gap is explicit and states why it matters.
  • There is one primary aim; objectives and hypotheses match the abstract, the Methods and any registration.
  • Sex and gender considerations are mentioned where relevant.
  • Terminology is consistent across title, abstract and text, and every claim cites a current, verifiable source.

09Writing the introduction for an international journal as an author in Germany

Align the aim with your approved protocol and ethics application so the introduction, the Methods and the ethics statement describe the same study (see Ethikkommission approval and publication in Germany). Use the present tense for established knowledge and the past tense for what you did; this is a convention, not a fixed rule, so check the journal’s instructions. If English is not your first language, have the introduction edited: it is the first section journal editors read in detail. For timing, see how long it takes to write a research paper.

Questions

How long should the introduction of a research paper be?
As a rule of thumb, four to five paragraphs and no more than about 10–15% of the total word count, within any journal limit.
What is the funnel structure in a research paper introduction?
A progression from broad context to a specific aim: context, current evidence, gap, then aim and design.
What is a gap statement?
A statement of what is unknown, limited or conflicting in current evidence and why that matters, which justifies your study.
Should the introduction include the hypothesis?
Yes, where there is one. Reporting guidelines such as CONSORT and STROBE ask authors to state objectives and prespecified hypotheses.
Should I write the introduction first or last?
Start with an outline and lead sentences; many authors refine the introduction after the Methods and Results are drafted so that the aim and gap match what was actually done.

References

  1. Cals, J. W. L., & Kotz, D. (2013). Effective writing and publishing scientific papers, part III: Introduction. Journal of Clinical Epidemiology, 66(7), 702. https://doi.org/10.1016/j.jclinepi.2013.01.004
  2. International Committee of Medical Journal Editors. (2026, January). Recommendations for the conduct, reporting, editing, and publication of scholarly work in medical journals. https://www.icmje.org/recommendations/
  3. Kotz, D., & Cals, J. W. L. (2013). Effective writing and publishing scientific papers—Part I: How to get started. Journal of Clinical Epidemiology, 66(4), 397. https://doi.org/10.1016/j.jclinepi.2013.01.002
  4. World Medical Association. (2025). World Medical Association Declaration of Helsinki: Ethical principles for medical research involving human participants. JAMA, 333(1), 71–74. https://doi.org/10.1001/jama.2024.21972
  5. Hopewell, S., Chan, A.-W., Collins, G. S., et al. (2025). CONSORT 2025 statement: Updated guideline for reporting randomised trials. BMJ, 389, e081123. https://doi.org/10.1136/bmj-2024-081123
  6. von Elm, E., Altman, D. G., Egger, M., Pocock, S. J., Gøtzsche, P. C., & Vandenbroucke, J. P. (2007). The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: Guidelines for reporting observational studies. The Lancet, 370(9596), 1453–1457. https://doi.org/10.1016/S0140-6736(07)61602-X
  7. Heidari, S., Babor, T. F., De Castro, P., Tort, S., & Curno, M. (2016). Sex and gender equity in research: Rationale for the SAGER guidelines and recommended use. Research Integrity and Peer Review, 1, Article 2. https://doi.org/10.1186/s41073-016-0007-6
Dr. CharliePubrica · Senior Medical Writer

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  • Published by Pubrica

How to cite this article

Dr. Charlie. (2026, November 10). How to Write the Introduction of a Research Paper: Funnel Structure, Gap Statement and Aim (with Examples). Pubrica. https://pubrica.com/academy/original-research-article/research-paper-introduction-funnel-gap-aim/

This article is general information for researchers, not legal, regulatory or funding advice. Check the current requirements of your journal, funder, ethics committee or regulator before you act on it.

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