A healthy, well-adjusted preschooler sits down at a table in front of a giant, freshly baked chocolate chip cookie. It's not a kitchen table -- it's Walter Mischel's Stanford lab during the late 1960s. The smell is heavenly.
"You see this cookie?" Mischel says. "You can eat it right now if you want, but if you wait, you can have two of them. I have to go away for five minutes. If I return and you have not eaten anything, I will let you have both cookies. If you eat this one while I'm gone, the bargain is off and you don't get the second one. Do we have a deal?" The child nods. The researcher leaves. What does the child do?
Mischel has the most charming, funny films of children's reactions. They squirm in their seat. They turn their back to the cookie (or marshmallow or other assorted caloric confections, depending on the day). They sit on their hands. They close one eye, then both, then sneak a peek. We took a camera into a preschool to see what would happen for ourselves:
The children in Mischel's experiment are trying to get both cookies, but the going is tough. If the children are kindergartners, 72 percent cave in and gobble up the cookie. If they're in fourth grade, however, only 49 percent yield to the temptation. By sixth grade, the number is 38 percent, about half the rate of the preschoolers.
Welcome to the interesting world of impulse control. It is part of a suite of behaviors under the collective term "executive function." Executive function controls planning, foresight, problem solving, and goal setting. It engages many parts of the brain, including a short-term form of memory called working memory.
Mischel and his many colleagues discovered that a child's executive function is a critical component of intellectual prowess. We now know that it is actually a better predictor of academic success than I.Q. It's not a small difference, either: Mischel found that children who could delay gratification for 15 minutes scored 210 points higher on their SATs than children who lasted one minute.
A child's brain can be trained to enhance self-control and other aspects of executive function. But genes are undoubtedly involved. There seems to be an innate schedule of development, which explains why the cookie experiment shows a difference in scores between kindergartners and sixth graders. Some kids display the behaviors earlier, some later. Some struggle with it their entire lives. It's one more way every brain is wired differently. But children who are able to filter out distractions, the data show, do far better in school.
Learn more about why in my new book, "Brain Rules for Baby: How to Raise a Smart and Happy Child from Zero to Five." Watch more parenting videos at brainrules.net.