Understanding your willpower

It makes sense, from an evolutionary perspective, that humans acquired the ability to defer gratification, persist in difficult or tedious tasks, and resist appealing but dangerous behaviors — all forms of willpower. Our primitive ancestors were, no doubt, more likely to survive if they could wait for berries to ripen before eating them, stand guard for hours over a campsite, and keep their hands off their neighbors’ mates.

In the 1960s, a famous experiment in which 4-year-olds were given the choice between eating one marshmallow right away or two marshmallows 15 minutes later suggested that, in modern times, willpower still confers certain advantages: The kids who held out for the larger treat grew up to be more popular, earned higher SAT scores and bigger salaries, and were less likely to be obese or abuse drugs.

Baumeister and Tierney point out that while some people — those very patient 4-year-olds, for example — have more innate willpower than others, willpower can be increased with repeated use. In one experiment, a group of college students instructed to focus on standing up straighter for two weeks did better on tests requiring persistence and self-discipline than peers who had not worked on improving their posture.

Willpower, though, is not only a skill that can be sharpened, but also a commodity that can be depleted. Many studies have shown that when people try for too long and too intensely to control themselves, or control themselves in too many different ways at once (quitting smoking and dieting at the same time, for example) their willpower tends to wane. This is particularly true when blood sugar levels are low.