Here’s the test: if you can name the researcher, use past tense. If you’re describing what “researchers” in general have been finding for years, use present perfect. “The contribution of agricultural production to greenhouse gas has long been debated” — not “was long debated.” Nobody debated it once and stopped; the debate is still running, and present perfect is the tense that says so.
This is Writing Tip 6, and it trips people up for a specific reason: both tenses are grammatically correct in almost every sentence you’d write. Nothing underlines red. The sentence just quietly says something you didn’t mean — either that a live debate is over, or that a single study is somehow still ongoing.
Named study, or general trend?
The whole rule turns on one question: are you talking about a specific, identifiable study, or an unnamed body of work?
When a study is specific — you can point to who did it and often when — simple past is what you want, and adding a date makes it non-negotiable: “Smith et al. conducted a two-year field experiment in 2009 and 2010 in rice paddies…” You wouldn’t write “have conducted” there. The experiment has an end date. It’s finished, it’s specific, and the sentence should sound finished too.
When you’re summarising a field rather than citing one paper, present perfect is usually the better fit, because the thing you’re describing hasn’t stopped: “The contribution of agricultural production to greenhouse gas has long been debated.” No named author, no end date — the debate is still active, present perfect says so, and switching this one to simple past would quietly close a question that’s still open.
The underlying logic is about specificity, not time. “Some researchers” isn’t specific. “Bouwman et al.” is. Once you can name the who, you’ve usually earned the right to name the when — and once there’s a when in the sentence, past tense is doing the honest job.
The exception: negative sentences
There’s one place present perfect wins even without a broad trend behind it: sentences that say something hasn’t happened yet. “Whether reducing potato crops is a viable strategy for reducing emissions has not yet been determined” reads naturally in present perfect and slightly oddly in simple past (“was not determined” sounds like someone tried and gave up, rather than that the question is still open). If your sentence is a gap in the literature rather than a finding in it, present perfect is usually the tense doing that gap justice.
Not the same call as Tip 7
It’s easy to mix this up with a different, related tense decision: inside a single citation sentence, whether the verb reporting a finding (“showed”) should be followed by a finding verb in past or present tense (“was associated” vs “is associated”). That’s a separate rule with its own logic, and it’s covered in the companion post on citing a specific study if you want it next. This one is about naming a study versus describing a field; that one is about two verbs in the same sentence doing different jobs.
There’s a short video on this too, on how the tense you pick changes the mood of the sentence, not just its grammar, if that’s an easier way in than reading it worked through.
A quick check for your own draft
Find every sentence in your introduction that starts with something like “researchers have” or “it has been shown” and ask: could I name who? If yes, and especially if there’s a date nearby, switch to past tense. If the honest answer is “several people, over years, and it’s still going,” leave it in present perfect. That one question resolves most of the cases that otherwise get fixed by guesswork.
It’s a small distinction, but it’s exactly the kind a second pair of eyes catches faster than the person who wrote the sentence — you know which sense you meant, a reviewer doesn’t. If you’d rather have someone go through the introduction for this and everything else around it, that’s what Academic English Editing Level 3 is for. There’s also a full chapter on it, How to Master Verb Tense in the Introduction Section, in Uni-edit’s book on fixing your academic English, if you want the longer version.
And if you’d rather these land in your inbox before the deadline than get found mid-panic, you can sign up for the writing tips — this is one of fifteen, and the rest cover the same kind of quietly-wrong-not-technically-incorrect problem.
A course on this, if enough people want one
Tips like this one are the raw material for Academic Writing Essentials, a short course we are thinking about building. It does not exist yet. If it would be useful, add your name and tell us what it should cover.
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