The Brain Loves a Surprise

NEW YORK (Reuters Health) - Scientists know that basic pleasures like good food and sex trigger the brain's ``reward system,'' but new research suggests that a pleasant surprise really gets the brain going.

The fact that some people rely on an orderly routine, while others thrive on never knowing what the day will bring, may have something to do with the brain's ``pleasure centers,'' researchers have found. In a brain-imaging study of 25 men and women, the investigators discovered that the predictability of a situation determined whether the brain's pleasure points were tweaked.

Dr. Gregory S. Berns of Emory University in Atlanta, Georgia, led the study. The findings are published in the April 15th issue of the Journal of Neuroscience.

In the study, Berns and his colleagues gave the participants drops of water and fruit juice. Part of the time, the sequence of water and juice drops was predictable, while at other points the sequence varied. It was at this time of unpredictability that the researchers noticed marked stimulation in the brain's pleasure centers in many, but not all, of the participants.

Surprisingly, Berns told Reuters Health, an individual's taste for water or juice had no bearing on brain stimulation. Although more than two thirds said after the tests that they preferred juice to water, their brain activity did not reflect their preference. Nor did water lovers show greater brain stimulation when they got their beverage of choice.

Instead, only the unpredictable drink sequence triggered a significant brain response, on average. ``That's what really lit up the reward system,'' Berns said.

Although this study could not delve into why a surprise dash of juice or water would stimulate the brain, Berns speculated that the activity in the brain's pleasure centers is linked to people's personalities. For instance, a person who craves twists and turns in life might show greater activity in response to a pleasant surprise than would a person who needs consistency.

An unpleasant surprise would have altogether different effects since it would not stimulate the brain's pleasure centers, Berns noted.

He also speculated that the brain's love of a surprise makes evolutionary sense. Only a few basics--such as food, water and sex--are ``natural rewards'' for animals, he said. It may be, according to Berns, that the brain is also primed to consider unpredictable events noteworthy. Being alert to out-of-the-ordinary conditions, he noted, is important to survival.

SOURCE: Journal of Neuroscience 2001;27.

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