Which AI Tool Tells You If Your Research Question Has Already Been Answered? (2026)

That split matters because the two failure modes are different. A question nobody has published on may still have four teams racing you, and only the register shows that. A question with no register entry may have been settled years ago in a published review your search terms never surfaced.

What does "already answered" mean for a literature review?

A research question counts as already answered when a published review or primary study has synthesised the evidence on a comparable population, exposure and outcome closely enough that repeating the work would add nothing new. PROSPERO, the international register of systematic review protocols produced by the Centre for Reviews and Dissemination at the University of York and funded by the National Institute for Health and Care Research (NIHR), applies that test at registration: before you can register, it shows you the registered reviews most similar to yours and asks you to check them. That is the practical standard. Not "has anyone touched this topic", but "is mine different enough from what is already registered".

Most postgraduate questions pass. A question narrowed to one country, one age band, one time window or one measurement instrument is usually different enough from the broad review that exists, and saying exactly how it differs is the work. If you are still shaping the question itself, how to write a research question covers the narrowing step before this check becomes useful.

How do I check whether someone has already registered a review on my question?

Search PROSPERO at crd.york.ac.uk/prospero before you start extracting data from papers. PROSPERO aims to "help prevent unintended duplication and research waste", registering a review is free, and before you can register it asks you to check the registered reviews it identifies as similar to your own. It also sets a hard timing rule: "Reviews must be registered before data extraction has started, or before individual participant data (IPD) have been received." So a register hit tells you not only that someone else is on your question, but that they committed to it before their data extraction began.

PROSPERO’s scope is narrower than most students expect, and that catches people out. PROSPERO "only accepts registrations of systematic reviews examining outcomes that are of direct relevance to human health and wellbeing", and it does not register "Literature reviews that use only a systematic search and no other systematic review methods" or "Scoping reviews (these may be incorporated in future)". So if you are writing a narrative literature review in education, management or the humanities, PROSPERO holds nothing on your question, and an empty result there is not evidence of novelty.

Source: PROSPERO, Centre for Reviews and Dissemination, University of York, read October 2026.

How do I check whether my question has already been answered in a published review?

Search the Cochrane Library at cochranelibrary.com. The Cochrane Library is owned by Cochrane and published by Wiley, and it is a set of separate databases: the Cochrane Database of Systematic Reviews holds Cochrane Reviews and protocols, with new and updated ones published continuously as they are ready, while the Cochrane Central Register of Controlled Trials holds trial reports and is published monthly. For a novelty check, the review database is the one that matters. A protocol there tells you a Cochrane team is already working on your question, and a finished review tells you it has been answered.

The Cochrane Library holds Cochrane’s own reviews, not every review publisher’s. A clean result there is one answer from one place, so search the main databases in your field for published systematic reviews as well before you call the question open.

Source: About the Cochrane Library, Cochrane.

Can Elicit or Consensus tell me whether my research question is new?

Neither Elicit nor Consensus answers the novelty question, because neither one searches review registers. What they do is shorten the reading. Elicit is strongest at finding and screening papers across a large corpus, and its free Basic tier covers search across its paper index plus limited usage of its Research Agent and Research Reports, with paid tiers listed on its own pricing page. Consensus is strongest at surfacing a fast evidence summary for a single question, which is useful when your question is already phrased as a yes or no claim. Consensus publishes its current free-plan caps on its own pricing page, and those caps are worth reading there rather than from a figure quoted in a blog post, including this one.

Where they beat Litrevu, plainly: if you have not yet gathered your papers, Elicit will build and filter that set far better than Litrevu will, because Litrevu starts from papers you have already chosen. Use Elicit or Consensus first, then come back. How to find a research gap walks through what to do with the papers once they are in front of you.

Sources: Elicit pricing, Consensus pricing, read October 2026.

Does Scite tell me whether the literature agrees on my question?

Scite answers a different and often more useful question: not whether your question has been asked, but whether the papers citing a given study support it or contrast with it. That citation context is the fastest way to find out that an apparently settled finding has been contested since publication, which is frequently where a still-open question hides. Scite is a paid product. As of October 2026 its pricing page lists no free plan and offers a 7-day free trial for new users, with its paid plans listed on that page.

For a one-off novelty check, the trial is enough. For a two-year thesis, a reference manager plus the free register searches will cover most of what you need, and Scite becomes worth paying for when your field has an active disagreement you need to map.

Source: Scite pricing, read October 2026.

Can Research Rabbit show me what has already been done?

Research Rabbit shows you the citation neighbourhood around papers you already have, which is how you find the adjacent work your keyword search missed. Its own site says it "analyzes papers you love and finds the research you’ve been missing", and it turns a seed paper into a visual map of related work. Sign-up is free, and the site says so directly: "Sign up - it’s free."

What Research Rabbit cannot do is tell you that a review is in progress, because an unpublished registered protocol has no citation network yet. Research Rabbit is a discovery tool, not a register. Pair it with the snowballing technique in citation chaining and it will surface the older review that answers your question in slightly different words.

Source: Research Rabbit.

Which tool should I use for which step?

Use a register for novelty, a review database for prior answers, a discovery tool for adjacent work, and a reading assistant only after the question survives all three. Free access below was read off each product’s own page in October 2026.

What does Litrevu do once the question is still open?

Litrevu is an AI research assistant that reads every paper a researcher adds, answers questions about them with a citation to the exact passage behind each claim, compares studies side by side, and checks the researcher’s own writing against their sources. Litrevu does not run a novelty check, does not search PROSPERO, and has no view on whether your question is new, because Litrevu answers only from the papers in your library. The point in the process where it helps is after the register search comes back clear and you have thirty or forty papers on your desk to read and compare.

Here is the shape of a cited answer to a question such as "How do these studies measure the outcome?", as a format illustration and not a real result. The tokens stand in for your own papers:

Three of the studies measure the outcome with
different instruments (Author, Year; Author, Year), while a
fourth reports a composite score (Author, Year). The
papers do not use a common measure, so their effect sizes
are not directly comparable.

Sources: [PDF 4, p. 7] [PDF 9, p. 2] [PDF 11, p. 14]

Every claim carries the page in the PDF it came from, and that page reference is the part you verify: open the passage and check the claim against it. The sentences in your review should be ones you wrote yourself. For a mechanical check on the reference list you end up with, the Litrevu reference checker tests up to 30 references per check against Crossref and OpenAlex with no account, and flags retractions Crossref carries from Retraction Watch.

How do I write up the fact that the question is still open?

Report the registration status explicitly and say what makes your question different, in the methods or in a short paragraph at the end of your review. PRISMA 2020, the reporting guideline published as Page and colleagues, BMJ 2021;372:n71 (DOI 10.1136/bmj.n71), runs to 27 items across seven sections, and it keeps a protocol and registration item, which the 2020 update moved into a new Other information section and expanded with a sub-item asking authors to describe amendments to what they registered. In practice that means a reviewer expects one of two sentences from you: the registration name and number, or a statement that the review was not registered.

For a Masters or doctoral review that does not qualify for PROSPERO, write the equivalent anyway: the registers and databases you searched, the date you searched them, and what you found. A supervisor reading the standard section order looks for that in the methodology, and a documented search date is what defends the review if a competing paper appears while you are writing.

Frequently asked questions