In decision making and psychology, decision fatigue refers to the deteriorating quality of decisions made by an individual after a long session of decision making. It is now understood as one of the causes of irrational trade-offs in decision making. For instance, judges in court have been shown to make poorer-quality decisions late in the day than they do early in the day. Decision fatigue may also lead to consumers making poor choices with their purchases.
There is a paradox in that "people who lack choices seem to want them and often will fight for them", yet at the same time, "people find that making many choices can be [psychologically] aversive."
Notably, major politicians and businessmen such as former United States President Barack Obama, Steve Jobs, and Mark Zuckerberg have been known to reduce their everyday clothing down to one or two outfits in order to limit the number of decisions they make in a day.
Trade-offs, where either of two choices have positive and negative elements, are an advanced and energy-consuming form of decision making. A person who is mentally depleted becomes reluctant to make trade-offs, or makes very poor choices. Jonathan Levav at Stanford University designed experiments showing how decision fatigue can leave a person vulnerable to sales and marketing strategies designed to time the sale. "Decision fatigue helps explain why ordinarily sensible people...can't resist the dealer's offer to rustproof their new car."
Dean Spears of Princeton University has argued that decision fatigue caused by the constant need to make financial trade-offs is a major factor in trapping people in poverty. Given that financial situations force the poor to make so many trade-offs, they are left with less mental energy for other activities. "If a trip to the supermarket induces more decision fatigue in the poor than in the rich - because each purchase requires more mental trade-offs - by the time they reach the cash register, they'll have less willpower left to resist the Mars bars and Skittles. Not for nothing are these items called impulse purchases."
Decision fatigue can lead people to avoid decisions entirely, a phenomenon called "Decision avoidance". In the formal approach to decision quality management, specific techniques have been devised to help managers cope with decision fatigue. Other forms of decision avoidance used to bypass tradeoffs and the emotional costs of decision making can include selecting either the default, or status quo options, where these are available.
Decision fatigue can influence irrational impulse purchases at supermarkets. During a trip to the supermarket, trade-off decisions regarding prices and promotions can produce decision fatigue, hence by the time the shopper reaches the cash register, less willpower remains to resist impulse purchases of candy and sugared items. Sweet snacks are usually featured at the cash register because many shoppers have decision fatigue by the time they get there. Florida State University social psychologist Roy Baumeister has also found that it is directly tied to low glucose levels, and that replenishing them restores the ability to make effective decisions. This has been offered as an explanation for why poor shoppers are more likely to eat during their trips.
Stanford University Professor of Psychology Carol Dweck found "that while decision fatigue does occur, it primarily affects those who believe that willpower runs out quickly." She states that "people get fatigued or depleted after a taxing task only when they believe that willpower is a limited resource, but not when they believe it's not so limited". She notes that "in some cases, the people who believe that willpower is not so limited actually perform better after a taxing task."
The "process of choosing may itself drain some of the self's precious resources, thereby leaving the executive function less capable of carrying out its other activities. Decision fatigue can therefore impair self-regulation". "[S]ome degree of failure at self regulation" is at the root of "[m]ost major personal and social problems", such as debt, "underachievement at work and school" and lack of exercise.
Baumeister and Vohs have suggested that the disastrous failure of men in high office to control impulses in their private lives may at times be attributed to decision fatigue stemming from the burden of day-to-day decision making. Similarly, Tierney notes that "C.F.O.s [are] prone to disastrous dalliances late in the evening", after a long day of decision-making.
With regard to self-regulation in legal regulation: One research study found that the decisions judges make are strongly influenced by how long it has been since their last break. "We find that the percentage of favorable rulings drops gradually from ?65% to nearly zero within each decision session and returns abruptly to ?65% after a break."