For fifteen years, productivity culture ran on a battery metaphor: self-control depletes like a muscle, so ration decisions, eat glucose, do hard things first. Then the flagship effect failed to replicate — spectacularly. The thesis: ego depletion as a depletable resource is likely false, and what replaces it is more useful: fatigue, beliefs, and attention explain “depleted” behavior better than an empty tank.

The collapse, in numbers

The original meta-analysis claimed a medium effect (d = 0.62). Then: bias-corrected re-analyses estimated ~zero (Carter & McCullough); a preregistered 23-lab replication (N = 2,141) found d = 0.04, CI spanning zero (Hagger et al., 2016); Many Labs 3 found nothing (Vadillo et al., 2018); and a 36-lab paradigmatic test (N = 3,531) found d = 0.06, data 4× likelier under the null (Vohs et al., 2021). Few psychological reversals are this complete.

What survives: fatigue is real, resource isn’t

People do perform worse after sustained effort — but the mechanism looks like shifting motivation and attention (boredom, opportunity costs, adenosine-linked fatigue signals), not a drained reservoir. Beliefs about willpower moderate outcomes; incentives restore “depleted” performance instantly (impossible if the tank were empty); rest, meaning, and autonomy replenish. The practical upshot inverts the old advice: instead of hoarding a finite budget, manage interest (make work engaging), friction (design defaults), and recovery (sleep, breaks, nature) — the variables with surviving evidence.

The counterpoint: don’t overcorrect

Null replications test narrow lab protocols, not all of self-control; tiny effects (d ≈ 0.08 in unpreregistered cuts) may exist below detection. And the battery metaphor, false or not, helped people rest without guilt and respect limits. Discard the mechanism, keep the compassion.

Takeaway

Stop asking “how much willpower do I have left?” and ask “why does this feel effortful?” — then fix the cause: unclear next action, boring framing, or genuine exhaustion. The tank was never real. The signal was.