Decision Fatigue: What It Is and What the Evidence Says

Decision fatigue is a good example of a psychological finding that entered popular culture confidently and then had a difficult decade in the replication literature.

The original claim

Ego depletion theory proposed that self-control draws on a limited resource depleted by use, so that exercising willpower on one task impairs performance on a subsequent unrelated one. A widely cited study of parole decisions reported that favourable rulings declined across a session and rose after breaks, which became the standard illustration. The framing implied that reducing daily decisions preserves capacity for important ones.

The replication problems

Large multi-laboratory replication efforts have found effects considerably smaller than originally reported, sometimes indistinguishable from zero. Meta-analyses accounting for publication bias substantially reduced the estimated effect. The parole study has been criticised on grounds including case ordering not being random. This does not mean nothing is happening, but the strong resource-depletion model is not well supported in its original form.

What remains useful

Alternative accounts propose that what changes is motivation and attention allocation rather than a depleted fuel supply - as a task continues, the appeal of continued effort declines relative to alternatives. Whatever the mechanism, the practical observations survive: people do make worse decisions when tired, hungry or at the end of long sessions, complex decisions do benefit from being scheduled when fresh, and reducing trivial choices does free attention. Keep the practices, hold the theory loosely.

Where a supplement fits here

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