The discovery was one of those fortunate accidents. Walter Mischel, a psychologist at Stanford, was interested in the stability of personality traits. In the late 1960s, he decided to study individual differences in young children’s ability to delay gratification.
His own daughters were preschoolers in the university’s Bing Nursery School. With their help, Mischel worked out the procedure for an experiment in self-control, using their classmates as subjects. He would place a marshmallow on a plate in front of a four-year-old and tell the child that he or she could earn a second marshmallow by waiting to eat the first one. This challenge is extremely difficult for a preschooler. Some children ate the marshmallow as soon as the researcher left the room, while others could wait as long as 15 or 20 minutes.
Mischel and his colleagues showed that they could increase the delay times for children who were weak in self-control by teaching them better strategies, like imagining the marshmallow was a cloud rather than a yummy treat. Many of the children with good self-control seemed to use these strategies spontaneously. Then he moved on to other experiments.
A decade later, as his daughters were chatting about their friends at dinner, he realized that the ones who were doing poorly in school were the same children who’d had short delay times in the old marshmallow experiment. He started asking about other children who had participated and realized that he needed to do a follow-up study.
Of the original 653 kids, Mischel managed to track down 185 when they were 15-18 years old. He found that good self-control in preschool predicted better SAT scores and ability to concentrate in high school, while poor self-control predicted later problems with self-regulation and coping with stress.
Self-control is a basic brain capacity that supports almost everything else that the brain does. The skills that make up self-control include cognitive flexibility (the ability to try a new approach when the old strategy isn’t working), resistance to distraction, and impulse control. These abilities help people to plan and organize behavior to achieve their goals.
Some of the individual differences in self-control are inherited, but it’s also possible to improve these abilities through practice, even in adulthood. Roy Baumeister showed that self-control is a limited resource, but like a muscle, it also grows stronger when it’s used.
Many parents will get a bigger payoff for building their children’s self-control than for trying to improve their intelligence. The reason is because most middle-class children already receive enough cognitive stimulation to develop intelligence close to its full potential. In contrast, many children have room to increase their self-control, and another long-term study suggests that doing so would improve their lives.
For more than three decades, Terri Moffitt, Avshalom Caspi and their colleagues followed one thousand people born in Dunedin, New Zealand in the early 1970s. Self-control from ages three to eleven was associated with more success at age 32 across a wide range of measures.
People with better childhood self-control were more likely to be in good financial shape and physically healthy as adults than those with worse self-control. Higher self-control also predicted a lower risk of becoming a single parent, a criminal, or a substance abuser. These differences existed even after variations in intelligence or social class were taken into account, and the long-term consequences of adolescent mistakes like dropping out of school or teen pregnancy accounted for only part of the effect.
In a group of British twins, the same researchers directly compared fraternal, same-sex pairs, who are as related as regular siblings but matched for age and gender. The twin with better self-control at age five had a lower risk of smoking, poor grades, and antisocial behavior at age twelve, despite sharing the same family environment.
The researchers found correlations between childhood self-control and adult success across the entire range of self-control, not just differences between people with poor self-control and everyone else. Being in the top 20% was better than being in the second quintile, and so on. This finding suggests that building self-control is likely to improve the lives of most kids—even the ones who are already above average at it.
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