A research gap is a question or problem that the existing literature has not adequately answered. It might be a topic nobody has studied, a population that has been repeatedly overlooked, a finding that conflicting studies leave unresolved, or a question that has only ever been examined with weak methods. Identifying a genuine gap is the foundation of every worthwhile study, every grant proposal, and every thesis, because research that does not fill a gap simply repeats what is already known.
This guide explains the types of research gap, where and how to find them, and how to turn an identified gap into a defensible research question.
The Main Types of Research Gap
Not all gaps are the same, and naming the type sharpens your thinking:
- Evidence gap. The literature is insufficient or contradictory. Studies disagree, or there are too few to draw a conclusion. This is the classic target of an evidence synthesis.
- Population gap. A condition or intervention has been studied in some groups but not others, for example trials conducted only in adults when the question concerns children, or only in high-income settings.
- Methodological gap. A question has been examined only with designs too weak to answer it, such as small uncontrolled studies where a randomised trial is needed, leaving room for stronger work.
- Contextual or temporal gap. A topic has not been studied in a particular setting, culture, or time period, so existing findings may not transfer.
- Theoretical gap. Existing theory does not fully explain an observed phenomenon, inviting new conceptual work.
A single project usually targets one type explicitly; being clear about which one makes the contribution legible to reviewers and funders.