Mind over marshmallows: Scientists find that self-motivators use less brain energy

Pearl Chiu stands in a hallway.
Pearl Chiu

In a classic study, a group of three- to five-year-olds faced a dilemma: eat the marshmallow now or wait for two. Researchers found that most of the children lost their willpower during the delay. Remarkably, the children who were best able to resist temptation were found, decades later, to be more successful in life. Now, Virginia Tech Carilion Research Institute scientists are beginning to understand why.

“The marshmallow test results suggest that brain and cognitive energy are resources that can be conserved or spent,” said Pearl Chiu, the assistant professor at the Virginia Tech Carilion Research Institute who led the new study, published in Cognitive, Affective, & Behavioral Neuroscience. “The more you have to work to resist the marshmallow, the more you deplete your willpower, and the less resources you have to continue resisting the marshmallow. It follows then, that the less willpower you deplete, the more you can continue to resist. Our finding supports this understanding.”

In the recent study, Chiu and her team, including researchers from Baylor College of Medicine, New York University, and the University of Rochester, found that people with more intrinsic motivation had less neural activity when doing simple puzzles. This suggests, Chiu said, that self-starters conserve brain energy, allowing them to work on tasks longer.

The test subjects worked on simple word puzzles while the researchers scanned their brains with functional magnetic resonance imaging. Participants were asked to work on the puzzles for nine minutes, after which they could choose to continue working on puzzles; undertake another activity, such as reading a newspaper; or lie in the scanner doing nothing.

The scientists measured how long the subjects continued to work on the puzzles during the free-choice period. Intrinsically-motivated people spent more time solving the puzzles. The scientists found that the study participants split evenly between people who were intrinsically motivated and not, and that the high and low intrinsic motivation groups were the same on variables such as age, gender, and education, among others.

“People with decreased neural responses during the task kept working on the puzzles even after the task was over, when they had options to do other things. That’s what we call intrinsic motivation,” said Chiu, who is also an assistant professor of psychology in Virginia Tech’s College of Science. “When we introduced an external monetary reward, they also worked more accurately.”

Chiu added that those with high neural activity during the task did not continue working on the puzzles when given the option during the free-choice period. Yet high neural activity appeared in the self-motivators after they made an error, but only if they had been promised a reward. With all types of motivation, Chiu said, people tend to slow down and increase their accuracy after they make an error to get back on track.

“People who are motivated intrinsically don’t use as many resources during the overall task itself, but when it came to critical events, such as correcting an error, they showed more neural responses and more accuracy,” Chiu said. “This suggests that generally using less neural or cognitive resources means you can harness those resources when you need them later, if you have the right incentives. At the very least, there is an interaction between internal and external motivation, and perhaps a person can strike the right balance between the two to work optimally, for both duration and accuracy.”

Scientists aren’t sure whether the neural activity begets the motivation levels or vice versa, Chiu said. Once the researchers begin to tease out the behavioral chicken from the developmental egg, they might be able to understand how to adjust motivation.

“Many psychiatric diseases are associated with motivation,” Chiu said. “Depression is associated with a lack of motivation. Addiction is hyper motivation – people want the reward, so to speak, of their drug and they will do a lot to get it.”

Chiu said it might be possible to “nudge” intrinsic motivation, to help people with depression and those with addictions.

With more research, scientists might be able to help kids wait for two marshmallows.

Written by Ashley WennersHerron