Lawyers quip that justice is ­what the judge ate for breakfast. New research suggests that justice might actually depend on when the judge ate breakfast.

Researchers at Ben Gurion University in Israel and Columbia University examined more than 1,000 decisions by eight Israeli judges who ruled on convicts’ parole requests. Judges granted 65 percent of requests they heard at the beginning of the day’s session and almost none at the end. Right after a snack break, approvals jumped back to 65 percent again.

Jonathan Levav, associate professor of business at Columbia, said that the judges could just be grumpy from hunger. But they probably also suffer from mental fatigue. Previous studies have shown that repeated decisions make people tired, and they start looking for simple answers. For instance, after making a slew of choices, car buyers will start accepting the standard options rather than continuing to cust­omize. As sessions drag on, judges may find it easier to deny requests and let things stand as they are.

Levav says he suspects a similar effect occurs in hospitals, university admissions offices or anywhere people make repeated decisions. So if you’re thinking about asking the boss for something special, you might want to do it right after a nice lunch.