This is a genuinely unusual case in psychology: a finding that held and an explanation that didn't.

The finding is the parole study. 1,112 rulings. 8 judges. 50 days. Favourable rulings ran at roughly 65% at the start of a session, declined steadily, and reached nearly zero by the end of it. After a break — food, rest — they returned to about 65%.

Read that as a defendant and it is genuinely alarming. The claim is that the strongest predictor of your outcome may not be your case.

The explanation offered was ego depletion: the theory that self-control is a limited resource which depletes with use, like a muscle. Decision fatigue is that theory applied to choosing.

And ego depletion has had one of the worst replication records in modern psychology.

A 2016 multi-lab Registered Replication Report, across roughly two dozen laboratories with 2,141 participants, found no effect. A further replication across 36 labs and 3,531 participants returned d = 0.06 — statistically indistinguishable from nothing. A 2015 reanalysis cut an earlier meta-analytic estimate from about 0.6 down to about 0.2, not significantly different from zero.

So where does that leave the judges?

The honest answer is: the pattern is real and the cause is open. Alternative explanations have been proposed — case ordering, how lawyers schedule, when judges break, the length of hearings. None is established either. What you have is a robust observation attached to a contested mechanism, which is a normal and healthy scientific state and a very bad basis for confident life advice.

One credit worth correcting while we're here. Baumeister did the self-control research. The phrase decision fatigue was popularised by the journalist John Tierney — the name came from the write-up, not the lab.

This page is educational and not a diagnosis. If difficulty deciding is persistent and affecting your life, a doctor or therapist is the right person to see.