Study Shows Judges are 65% More Likely to Grant Parole After Lunch

The purpose of this study was to prove that judges can be influenced by irrelevant factors. The researcher's were trying to debunk ‘legal formalism’ and pave the way for ‘legal realism.’

Legal formalism holds that judges apply legal reasons to the facts of a case in a rational, mechanical, and deliberative manner. In contrast, legal realists argue that the rational application of legal reasons does not sufficiently explain the decisions of judges and that psychological, political, and social factors influence judicial rulings.

The Study

The researcher's, Shai DanzigerJonathan Levav, and Liora Avnaim-Pesso, gathered data on parole decisions by experienced judges. After examining over 1000 decisions, they found that judges have a 65% chance of granting parole after a rest. However, as time goes by, the probability reduces all the way down to zero.

To repeat, after a judge’s food break, the probability of being granted parole is at 65%. Just before the break, zero.

The Science

When people become mentally depleted, they’re more likely to favour the status quo.

In our case, as the judges became more mentally depleted, they gradually decided in favour of the default position. As it’s safer to leave criminals in prison, the default position became a rejection of parole.

Answers to Possible Objections:

The researchers examined other possibilities: the ‘severity of crime, months served, previous incarcerations, and rehabilitation program, prisoner demographics (sex, nationality), and the proportion of favorable rulings to that point in the day.’

They found no correlation. However, they did find two additional insights:

  • Prisoners that were on a rehabilitation program were more likely to be granted parole;

  • As expected, prisoners that offended multiple times, were less likely to be granted parole.


It is better to be positioned at the beginning of a court session if the prisoner’s request deviates from the default decision.

Judges are not purely rational. Just like the rest of us, they can be influenced by irrelevant factors.

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Extraneous factors in judicial decisions by Shai Danziger, Jonathan Levav, and Liora Avnaim-Pesso