Tierney looks at the results of years of work by Roy Baumeister, at Case Western and then at Florida State, and some of his colleagues and former students, but introduces that work with a startling study from Israel. There the decisions of an Israeli parole board were examined for patterns: would Arab Israelis, say, get tougher sentences than Jewish Israelis? No, it turned out. Instead, a different and quite unexpected pattern emerged: cases heard in the first part of the mornings and just after lunch were far more likely to be granted parole than cases heard late mornings or late afternoons: “Prisoners who appeared early in the morning received parole about 70 percent of the time, while those who appeared late in the day were paroled less than 10 percent of the time.” The parole board turned out to be a poster case for decision fatigue.
What Baumeister’s experiments with mental discipline had demonstrated was that there’s “a finite store of mental energy for exerting self-control”; will-power is “a form of mental energy that [can] be exhausted.” His results were confirmed in an ingenious experiment conducted in German car dealerships. There, customers ordering options for their new sedans turned out to have their choices strongly affected by the order and complexity of the options offered—to the tune of more than 1,500 euros. “Whether the customers paid a little extra for fancy wheel rims or a lot extra for a more powerful engine depended on when the choice was offered and [therefore] how much willpower was left in the customer.”
So it was with the Israeli parole board. Granting parole is a decisive action, an uneasy choice that carries risk: the offender may reoffend and again tear at the social fabric. Withholding parole preserves the status quo while keeping the parole option for later. In a way, it’s a decision not to decide. So, while their supply of willpower was good, the board could grapple with parole decisions on their complex individual merits; as they exhausted their supply of mental energy for self-control, they fell back on mental shortcuts, on safety, on putting off more mental struggle.
Just how was it, though, that willpower got resupplied overnight—and at lunchtime? Glucose, Baumeister’s lab was able to demonstrate. Again and again in their experiments, sugary lemonade restored willpower, but a control drink of artificially sweetened lemonade did not. The effect was even confirmed in dogs, in studies done at the University of Kentucky by Holly Miller and Nathan DeWall: “After obeying sit and stay commands for ten minutes, the dogs performed worse on self-control tests and were also more likely to make the dangerous decision to challenge another dog’s turf. But a dose of glucose restored their willpower.”
For overshoppers, the implications of decision fatigue are significant. Baumeister’s studies “show that people with the best self-control are the ones who structure their lives so as to conserve willpower. Instead of deciding every morning whether or not to force themselves to exercise, they set up regular appointments to work out with a friend. Instead of counting on willpower to remain robust all day, they conserve it so that it’s available for emergencies and important decisions.” Overshoppers need to husband their self-control by structuring their lives. In “Decision Fatigue: Part 2” we’ll look at some examples of how they might do that.