Where the term comes from
Popularised through Roy Baumeister's ego-depletion research from the late 1990s onward, which held that self-control draws on a limited resource.
Why it matters
It is asserted as settled science across most productivity writing. A 23-lab preregistered replication (Hagger et al., 2016) found the effect statistically indistinguishable from zero, and Baumeister and Vohs published a rebuttal disputing the paradigm. The disagreement is unresolved.
The common mistake
Citing it as established fact. The subjective experience is real; the willpower-reserve explanation is not well supported. Cognitive load and unresolved goals account for the same experience with better evidence.
What it looks like in practice
You reach 6pm, look at the same list you looked at that morning, and cannot face choosing. The feeling is real. Whether it is a depleted willpower reserve or simply eleven unresolved items still competing for attention makes a difference to what actually helps: rest, or writing them down and ordering them.
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Frequently asked questions
What is decision fatigue?
Decision fatigue is the proposed decline in decision quality after making many decisions, derived from the ego-depletion model — a model that failed a large preregistered multi-lab replication.
What's the most common mistake with decision fatigue?
Citing it as established fact. The subjective experience is real; the willpower-reserve explanation is not well supported. Cognitive load and unresolved goals account for the same experience with better evidence.