Somewhere along the way, “decision fatigue” turned into one of those ideas everyone just accepts without checking.
The version that gets repeated in bestselling books, keynote talks, and countless productivity think-pieces goes roughly like this: the more decisions a person makes in a day, the worse their judgment gets, and by the afternoon even trained professionals are running on fumes. It’s a tidy story, and it’s the kind of thing that sounds true because it matches how tired we all feel by four in the afternoon.
A study published in Communications Psychology went looking for that effect in real professional decisions, at a scale most decision fatigue research never gets close to. It didn’t find it.
What researchers actually tested
Researchers at Linköping University in Sweden, led by David Andersson, examined 231,076 real phone calls handled by 174 specialized nurses at 1177, Sweden’s national telephone triage and medical advice service, across two separate three-month stretches in 2021 and 2022.
Every one of those calls ended in a real clinical judgment: whether to tell the caller to go to an emergency room, book a regular appointment, or manage things at home. If decision fatigue were the powerful, everyday force it’s often described as, a dataset like this, hundreds of thousands of real triage calls made by the same working nurses across full shifts, is exactly where it should show up.
It didn’t. The researchers were direct about it: “We thus found no evidence for decision fatigue.” That’s not a hedge or a soft null result buried in a footnote. It’s the study’s own summary of what 231,076 calls told them.
Why a null result here is actually a strong result
Researchers have a specific statistical tool for telling the difference between “we didn’t find an effect” and “we have real evidence there isn’t one,” and this study leaned on it.
Using Bayesian analysis, the team reported that “the results consistently showed relative support for the statistical null hypothesis of no difference in decision-making depending on fatigue,” with Bayes factors strong enough to count as real, positive evidence for no effect, not just an absence of proof either way.
The Bayes factors reported across the study’s main tests were all above 22, a threshold researchers generally treat as strong evidence, not a coin flip. That distinction matters because a lot of the popular version of decision fatigue rests on smaller studies, some of them decades old, that were never built to rule the effect out this cleanly, and on a handful of vivid individual examples that popular writing has stretched into a general rule about every profession that involves back-to-back decisions.
A big, unglamorous dataset of real triage calls doesn’t make for as good a keynote slide as a dramatic lab experiment, but it’s a far harder thing to argue with.
The authors put their conclusion plainly: the findings “cast serious doubt on the empirical relevance of decision fatigue as a domain general effect.” Domain general is the key phrase there. This isn’t a claim that no one, anywhere, ever gets worse at a task late in a shift. It’s a challenge to the sweeping version of the idea, the one that gets applied to judges, doctors, hiring managers, and everyone else who makes a lot of calls in a day, as if it were settled science.
Where this leaves the rest of us who make a lot of small calls
I’m not a nurse or a doctor, and nothing here is meant as guidance about anyone’s medical care. But I spend a good chunk of most days making a version of the same repetitive judgment call, over and over, just in a completely different field: which headline actually earns a click, which draft is ready and which one needs another pass, which traffic dip is a real problem and which one is noise.
It’s the kind of work where it would be easy to assume my fifteenth decision of the day is worse than my third, purely because I’ve heard that story enough times to believe it about myself without ever actually checking.
What this study suggests, at least for one very real, very repetitive kind of professional judgment, is that the story might be doing more work than the evidence supports. My own instinct, watching myself work through a stack of titles or edits, has always been that the problem isn’t a depleting well of willpower. It’s more often that I’ve stopped looking at the actual thing in front of me and started running on autopilot, which is a different problem with a different fix: slow down and look again, not simply rest more and hope the well refills.
That reframe changes what I actually do about a sluggish afternoon. Instead of treating a bad hour of editing as proof my judgment has quietly degraded since morning, and instead of automatically assuming a short break will fix whatever’s wrong, I’ve started asking a plainer question first: am I actually still paying attention to this specific decision, or have I started pattern-matching it against the last nine that looked similar. Most of the time it’s the second one, and the fix for that has nothing to do with willpower running low. It’s closer to a deliberate reset, reading the actual headline again instead of skimming past it because I’ve seen forty like it this week.
None of this means fatigue in general is a myth, or that rest doesn’t matter. It means one specific, very popular claim about how fatigue supposedly wrecks professional judgment over the course of a day didn’t hold up against 231,076 real decisions, which is a lot more evidence than most of the claim’s popularizers ever bothered to check. The next time a tidy psychological claim shows up dressed as an unquestionable fact, that’s worth remembering before repeating it as one.
