Decision Fatigue Exhausts the Judge

This 2011 PNAS study by Danziger, Levav, and Avnaim-Pesso examined 1,112 parole board rulings made by eight Israeli judges over 50 days to test whether extraneous, non-legal factors influence high-stakes expert decisions. The researchers tracked each case's legal merits (crime severity, prior incarcerations, availability of rehabilitation programs) alongside the case's position in the day's docket relative to the judges' two food breaks (a morning snack and lunch). They found that the probability of a favorable (parole-granting) ruling started near 65% at the beginning of a session, declined gradually to nearly 0% by the end of the session, and then jumped back up to about 65% immediately after each break. This pattern held consistently across all eight judges and remained significant after controlling for legal case variables, indicating it was not explained by case difficulty or docket ordering alone. Judges heard between 14 and 35 cases per day (averaging about 22.6), and the depleting favorable-ruling rate tracked the number of cases heard since the last break rather than time of day per se. The authors interpret the findings as evidence of decision fatigue or mental depletion: as judges make more sequential decisions without rest, they default to the cognitively easier, status-quo option, which in a parole hearing is denial. The study is widely cited as real-world evidence that even trained experts making consequential rulings are vulnerable to a psychological/physiological factor unrelated to the legal facts of a case.