Willpower

healthier teeth. (Apparently, good self-control includes brushing and flossing.) Self-control was irrelevant to adult depression, but its lack made people more prone to alcohol and drug problems. The children with poor self-control tended to wind up poorer financially. They worked in relatively low-paying jobs, had little money in the bank, and were less likely to own a home or have money set aside for retirement. They also grew up to have more children being raised in single-parent households, presumably because they had a harder time adapting to the discipline required for a long-term relationship. The children with good self-control were much more likely to wind up in a stable marriage and raise children in a two-parent home. Last, but certainly not least, the children with poor self-control were more likely to end up in prison. Among those with the lowest levels of self-control, more than 40 percent had a criminal conviction by the age of thirty-two, compared with just 12 percent of the people who had been toward the high end of the self-control distribution in their youth.
    Not surprisingly, some of these differences were correlated with intelligence and social class and race—but all these results remained significant even when those factors were taken into account. In a follow-up study, the same researchers looked at brothers and sisters from the same families so that they could compare children who grew up in similar homes. Again, over and over, the sibling with the lower self-control during childhood fared worse during adulthood. They ended up sicker, poorer, and were more likely to spend time in prison. The results couldn’t be clearer: Self-control is a vital strength and key to success in life.

Evolution and Etiquette
    As psychologists were identifying the benefits of self-control, anthropologists and neuroscientists were trying to understand how it evolved. The human brain is distinguished by large and elaborate frontal lobes, giving us what was long assumed to be the crucial evolutionary advantage: the intelligence to solve problems in the environment. After all, a brainier animal could presumably survive and reproduce better than a dumb one. But big brains also require lots of energy. The adult human brain makes up 2 percent of the body but consumes more than 20 percent of its energy. Extra gray matter is useful only if it enables an animal to get enough extra calories to power it, and scientists didn’t understand how the brain was paying for itself. What, exactly, made ever-larger brains with their powerful frontal lobes spread through the gene pool?
    One early explanation for the large brain involved bananas and other calorie-rich fruits. Animals that graze on grass don’t need to do a lot of thinking about where to find their next meal. But a tree that had perfectly ripe bananas a week ago may be picked clean today or may have only unappealing, squishy brown fruits left. A banana eater needs a bigger brain to remember where the ripe stuff is, and the brain could be powered by all the calories in the bananas, so the “fruit-seeking brain theory” made lots of sense—but only in theory. The anthropologist Robin Dunbar found no support for it when he surveyed the brains and diets of different animals. Brain size did not correlate with the type of food. Dunbar eventually concluded that the large brain did not evolve to deal with the physical environment, but rather with something even more crucial to survival: social life. Animals with bigger brains had larger and more complex social networks. That suggested a new way to understand Homo sapiens. Humans are the primates who have the largest frontal lobes because we have the largest social groups, and that’s apparently why we have the most need for self-control. We tend to think of willpower as a force for personal betterment—adhering to a diet, getting work done on time, going out to jog, quitting smoking—but that’s probably not the primary reason it evolved so fully in our ancestors. Primates are social beings who have to control themselves in order to get along with the rest of the group. They depend on one another for the food they need to survive. When the food is shared, often it’s the biggest and strongest male who gets first choice in what to eat, with the others waiting their turn according to status. For animals to survive in such a group without getting beaten up, they must restrain their urge to eat immediately. Chimpanzees