Courtesy Duke University Medical Center and World Science staff
Recordings of brain cells have found that monkeys take note of missed opportunities and learn from their mistakes, scientists say.
“This is the first evidence that monkeys, like people, have ‘would-have, could-have, should-have’ thoughts,” said Ben Hayden of Duke University Medical Center in Durham, N.C., lead author of the study published in the research journal Science.
The researchers watched individual neurons in a region of the brain called the anterior cingulate cortex that monitors the consequences of actions and mediates resulting changes in behavior. The monkeys were making choices that resulted in different amounts of juice as a reward.
Their task was like the TV show “Let’s Make a Deal” with the experimenters offering monkeys choices from an array of hidden rewards. During each trial, the monkeys chose from one of eight identical white squares arranged in a circle. A color beneath the white square was revealed and the monkey received the corresponding reward.
Over many weeks, the monkeys were trained to associate a high-value reward with the color green and the low-value rewards with other colors. After receiving a reward, the monkey was also shown the prizes he missed.
The researchers found that brain cells become activated in proportion to the reward—a greater reward caused a higher response. They also found that these same brain cells, called neurons, responded when monkeys saw what they missed. Most of these neurons responded the same way to a real or imagined reward.