When academic writers move from surveying prior work to justifying their own study, they rely on a recognizable set of phrases — “however, little is known about…”, “to date, no research has examined…”, “this raises the question of…” — to signal that a gap exists and that it is worth filling. These are discourse markers: words and phrases that don’t add propositional content on their own but signal the logical relationship between what came before and what comes next. Used well, they make the structure of an argument easy for a reader to follow. Used as unexamined filler, they can make a genuine gap claim look like a formula pasted in without real justification.
This guide covers the specific phrases researchers use to introduce a research gap, the rhetorical structure those phrases typically serve, and how to use the convention effectively rather than mechanically. It assumes you already know how to structure an introduction section and write a literature review — see Structuring the Introduction of a Research Paper and How to Write a Literature Review for a Research Paper for that groundwork. This page scopes narrowly to the language used at the specific moment a writer pivots from “here is what is known” to “here is what is not.”
Why this move needs its own discourse markers
A research gap statement does real argumentative work: it has to acknowledge the existing literature (so the claim of novelty is credible, not naive), then pivot to what that literature has not established, then imply — without necessarily stating outright — that the study to follow addresses it. That pivot is a logical turn, and readers rely on discourse markers to register the turn is happening. A gap statement dropped in without a signaling phrase reads as a non sequitur; a gap statement signaled by the wrong marker (a marker of addition or example where a marker of contrast or negation is called for) confuses the logical relationship even if the underlying claim is sound.
The rhetorical structure: Swales’ CARS model
The most widely taught account of this move comes from applied linguist John Swales, whose CARS model (“Create a Research Space,” from his 1990 book Genre Analysis: English in Academic and Research Settings) describes research-article introductions as typically accomplishing three rhetorical “moves”:
- Move 1 — Establishing a territory. The writer situates the topic as important, active, and well studied, usually by citing prior work.
- Move 2 — Establishing a niche. The writer identifies a gap in that territory — a limitation, an unanswered question, a contradiction, or an extension nobody has made yet. This is the move where research-gap discourse markers do their work.
- Move 3 — Occupying the niche. The writer states how the present study fills the gap just identified, often with explicit purpose or research-question statements.
Discourse markers that introduce a research gap are, in Swales’ terms, the linguistic signal that Move 1 has ended and Move 2 has begun. Recognizing this is useful beyond vocabulary: it explains why a gap statement almost always follows a summary of existing literature rather than opening the introduction cold, and why it’s almost always followed immediately by a purpose statement (Move 3) rather than left hanging. If your gap sentence doesn’t have a Move 1 summary before it or a Move 3 purpose statement after it, the marker alone won’t make the paragraph read as coherent — the surrounding structure has to be there too. For a fuller treatment of how these three moves fit into the introduction as a whole, see Structuring the Introduction of a Research Paper.
Common discourse-marker patterns for introducing a gap
These cluster into a few recognizable functional types. None is inherently better than another — the right choice depends on precisely what kind of gap you’re describing.
Contrastive / counter-expectation markers
These signal that what follows cuts against the expectation set up by the preceding literature summary: however, yet, nonetheless, despite this, despite this body of work, notwithstanding these advances, in contrast, on the other hand. They work best when Move 1 has actually established a positive expectation (a well-developed area, consistent findings, a widely used method) for the gap to contrast against.
Negation-based markers
These state the absence of prior work directly, usually with a scope qualifier: little is known about…, few studies have examined…, no research to date has investigated…, this has not been systematically examined…, remains poorly understood, remains unclear, has received limited attention. These are the most literal gap markers and also the riskiest — an absolute claim (“no research has examined X”) is a factual claim that a reviewer familiar with the field can falsify with a single counter-citation. Scope and hedge these carefully (see the section below).
Question-raising markers
These frame the gap as an open question rather than an absence: this raises the question of…, it remains an open question whether…, whether X holds under Y conditions has not been established. This framing is often a better fit when the gap is genuinely a matter of unresolved evidence (studies point different directions) rather than a matter of nobody having looked yet.
Extension / limitation markers
These position the gap as a boundary condition on existing work rather than a total absence: studies to date have focused primarily on X rather than Y, prior work has largely been limited to…, existing research has not extended this to…, these findings have yet to be replicated in…. This is usually the most defensible pattern when a real literature exists and your contribution is a meaningful extension of it — because it doesn’t require claiming an absence, only a boundary.
An illustrative example
The following is an illustrative composite written to show the pattern in context, not a quotation from any specific published paper.
“Prior work has established that [Method A] reliably improves [Outcome] in [Population 1] (Territory / Move 1, citations). However, whether this effect holds in [Population 2] remains unclear (Niche / Move 2, contrastive + negation markers). This study addresses that question by [brief description of approach] (Occupying the niche / Move 3).”
Notice the marker (“however… remains unclear”) does not do the persuasive work by itself — it is only convincing because the sentence before it actually established a specific, cited claim for the gap to contrast against, and the sentence after it commits to a specific way of addressing the gap. The phrase is a hinge, not a substitute for the argument on either side of it.
Using these conventions effectively — and authentically
These phrases are genre conventions, which is exactly why they’re easy to overuse without checking whether they’re true. Some practical guidance:
- Scope absolute claims narrowly. “No research has examined X” is safer, and usually more accurate, as “no research has examined X in [specific population / context / method].” A narrower, well-scoped gap claim is both more defensible to a reviewer and more useful to the reader, because it tells them exactly what’s new.
- Make sure the gap is real, not just unclaimed. A topic no one has studied is not automatically a gap worth filling — it may be unstudied because it isn’t a meaningful question. The marker signals a gap exists; it doesn’t establish that the gap matters. That argument has to be made in the surrounding sentences (why does closing this gap matter for the field or for practice?).
- Match the marker to the actual logical relationship. If the literature genuinely conflicts (some studies find X, others find not-X), a question-raising marker (“whether X holds has not been resolved”) is more accurate than a negation marker implying nobody has looked. Misrepresenting disagreement as absence is a common and avoidable error.
- Don’t stack markers. “However, despite this, little is known…” layers three signals of the same underlying move and reads as padding rather than precision. One clear marker, correctly matched to the relationship, is stronger than several redundant ones.
- Let Move 3 follow closely. A gap statement that isn’t followed by a purpose or research-question statement leaves the reader wondering why they were told about the gap at all. The marker’s rhetorical job is to set up the sentence that follows it, not to conclude a paragraph.
- Verify the claim before you submit, not after a reviewer does. Because negation markers are checkable factual claims, do a genuine search of the recent literature in your specific sub-area before asserting one — reviewers in most fields will catch an inaccurate “no prior work” claim, and it costs credibility with the rest of the manuscript.
Frequently asked questions
What is a discourse marker, in plain terms?
A discourse marker is a word or phrase that signals the logical relationship between one piece of text and the next — contrast, addition, cause, consequence, and so on — without itself adding new factual content. “However,” “therefore,” and “in contrast” are all discourse markers; the research-gap phrases covered on this page are a specific functional subset used at a specific point in an introduction.
Is the CARS model the only accepted account of this structure?
It’s the most widely taught and cited framework for research-article introductions in genre analysis and English-for-academic-purposes pedagogy, originating with John Swales’ 1990 Genre Analysis and elaborated in his later work. Discipline- and genre-specific variation exists — humanities and qualitative papers, for instance, often deviate from a strict three-move pattern (see How Qualitative Research Papers Deviate from IMRaD Structure) — but the territory-niche-occupation logic is a reliable default for interpreting how gap statements function structurally.
Is it acceptable to claim “no research has examined” something?
Only if it’s true and you’ve checked. Treat it as a factual, falsifiable claim rather than a stock phrase — scope it precisely (by population, method, context, or time period) so it stays accurate, and be prepared for a reviewer to test it against their own knowledge of the field.
How is this different from a literature review?
The literature review establishes Move 1 (the territory) — what is already known and cited. The gap statement is the specific pivot sentence or short passage, usually near the end of the introduction, that turns that summary into a justification for the present study. See How to Write a Literature Review for a Research Paper and, for dissertation-length work specifically, The Literature Review Chapter of a Dissertation for the fuller review-writing process this feeds into.
