Marshmallow temptations, brain scans could yield vital lessons in self-control

It is a simple test, but has surprising power to predict a child's future. A 4-year-old is left sitting at a table with a marshmallow or other treat on it and given a challenge: Wait to eat it until a grown-up comes back into the room, and you'll get two. If you can't wait that long, you'll get just one.

Some children can wait less than a minute, others last the full 20 minutes. The longer the child can hold back, the better the outlook in later life for everything from SAT scores to social skills to academic achievement, according to classic work by Columbia University psychologist Walter Mischel, who has followed his test subjects from preschool in the late 1960s into their 40s now.

From church sermons to parenting manuals, "the marshmallow test" has entered popular culture as a potent lesson on the rewards of self-control. It has also raised deep psychological research questions: What is involved in delaying gratifica tion? Why does it correlate with success in life? Why do people fail at it?

Now neuroscientists, using high-tech brain scans, are seeking to answer these questions by examining what goes on in the brain when a person aces or flunks marshmallow-type tasks. They aim to use their findings to figure out how to train people to control themselves better, whether that means focusing on the potential pitfalls of a mortgage broker's pitch or concentrating on the calorie count of a brownie.

"Brain imaging provides a very exciting and important new tool," Mischel said. What matters, he said, is not which areas of the brain light up on scans, but the clues that brain activity may provide to the psychological mechanisms involved: Is the problem in how you perceive a temptation, for example, or in an underlying inability to stop yourself?

Most recently, Yale University researchers found that delaying gratification involves an area of the brain, the anterior prefrontal cortex, that is known to be involved in abstract problem-solving and keeping track of goals. For example: You want to drive across town, so you find your keys, start your car, and navigate the route, all while that critical brain region keeps the overarching trip goal in your mind.

The brain scan findings from 103 subjects suggest that delaying gratification involves the ability to imagine a future event clearly, said Jeremy Gray, a Yale psychology professor and coauthor of the study in the September edition of the journal Psychological Science. You need "a sort of 'far-sightedness,' to put it in a single word," he said.

In the coming months, researchers plan to perform brain scans on 40 of the original subjects of Mischel's marshmallow test, said John Jonides, a psychology professor and brain imager at the University of Michigan who is working with Mischel on the project.

If brain differences are found between good and poor delayers, he said, they could suggest effective avenues for training. For example, if brain regions involved in attention make a difference, poor delayers could be trained to focus their attention more effectively and fight distractions.

"Or, if we find that the problem seems to be associated with regions involved in ridding your short-term memory of unwanted information (i.e., getting the marshmallow out of mind so that you can wait for two of them), then perhaps training to improve control over short-term memory might be something to try," Jonides said in an e-mail.

Mischel, among others, believes that the key to delaying gratification may lie in the ability to "cool the hot stimulus," he said in a telephone interview. He and colleagues are exploring the possibility of teaching children that skill in schools.

Over and over, research is showing that the trick is to shift activity from "hot," more primitive areas deep in the brain to "cool," more rational areas mainly in the higher centers of the brain, he said.

There are many ways to cool a hot stimulus, said Mischel, who is president of the Association for Psychological Science. Say you are determined to resist the chocolate cake at a restaurant. You must distract yourself from the waiter's dessert tray. You can also focus on long-term consequences and make them "hot" - by vividly imagining your future tummy and hip bulges - or think of the cake in the cooler abstract, as a thing that will make you fat and clog your arteries.

In the marshmallow test, he said, "the same child who can't wait a minute if they're thinking about how yummy and chewy the marshmallow is can wait for 20 minutes if they're thinking of the marshmallow as being puffy like a cotton ball or like a cloud floating in the sky."

Neuro-economists, who use brain scans to shed light on economic decision-making, are also exploring the "cool brain hot brain" theory, said Daniel Benjamin, an assistant professor of economics at Cornell University.

If that model is borne out, he said, it could hold important implications for economics. Economists traditionally think that people's preferences naturally reflect their best interests. But if their impulsive brain leads them to make poor choices, "then there's a whole realm of situations where some kind of intervention, whether by government or by employers, might be appropriate," he said.

Already, he said, such thinking is leading to experiments like the website stickk.com, which tries to help people use their "cool" brain to overcome impulses by letting them stake money on goals they aim to achieve. If a user wants to lose 20 pounds, for example, he might choose to put $200 down and receive $10 back each week he loses 1 pound.

Such experiments are exciting, Benjamin said, because they avoid paternalistic government intervention. Instead, "They allow individuals themselves, during cool periods, to regulate the way they will behave during hot periods."

Research has found that the ability to delay gratification is linked not just to cool headedness and farsightedness, but to intelligence as well. The relationship appears complex, however; intelligence is hard to define, and when a child is both smart and good at delaying, it is hard to distinguish cause from effect.

Four-year-olds who ace the marshmallow test may then translate their self-control into academic effort that makes them score higher on intelligence tests; or, it could be that being smart helped them figure out how to distract themselves from the marshmallow.

Mischel emphasized that though intelligence is related to doing well on marshmallow tests, it is by no means the whole answer.

As many people know, "It's quite possible to be very smart and not able to inhibit your impulses," he said.

Carey Goldberg can be reached at goldberg@globe.com.