Decision fatigue helps explain why ordinarily sensible people get angry at colleagues and families, splurge on clothes, buy junk food at the supermarket and can't resist the dealer's offer to rustproof their new car. No matter how rational and high-minded you try to be, you can't make decision after decision without paying a biological price. It's different from ordinary physical fatigue -- you're not consciously aware of being tired -- but you're low on mental energy. The more choices you make throughout the day, the harder each one becomes for your brain, and eventually it looks for shortcuts, usually in either of two very different ways. One shortcut is to become reckless: to act impulsively instead of expending the energy to first think through the consequences... The other shortcut is the ultimate energy saver: do nothing. Instead of agonizing over decisions, avoid any choice.
I think this is something we're all aware of, at least to some extent. There are some fascinating studies in this article that go to show the huge aggregate affect this sort of fatigue can have on people, including, for example, parole board judges. It seems there's a huge disparity with respect to the probability of parole between those prisoners who go before the parole board in the morning and those who are assigned an afternoon slot, because the judges simply tire of making these tough decisions.
When I read this I immediately thought of law school. I studied computer engineering in undergrad, and on those exams you knew that if you came up with the right answer--and 99% of the time there was only one right answer--you'd get full marks for the problem. But, in law school, scoring often is done a bit differently, and usually takes a number of things into account (e.g., ability to spot the issues, reasoning skills, proper use of the facts, cogency, etc.).
The difference then is subjectivity--law professors simply have more latitude when grading than do engineering professors, and consequently, are required to make more decisions as they pore over exam answers. Knowing this, at least at an intuitive level, some of us struggled with when to turn in our completed exams. Will she grade them in order? Will she turn the stack of exams over before she starts? Will she grade them over a few days or in a single night? Will she be drinking while she grades them? Will she grade them on campus or at home where her kids will be fighting for her attention?
Of course no one lost sleep over this sort of thing, but I'd be lying if I said I never thought about it.
Another really interesting takeaway from the article is this bit about poverty:
Spears and other researchers argue that this sort of decision fatigue is a major -- and hitherto ignored -- factor in trapping people in poverty. Because their financial situation forces them to make so many trade-offs, they have less willpower to devote to school, work and other activities that might get them into the middle class.