Monkeys learn from mistakes: study

CHICAGO – Monkeys are able to learn from their mistakes and will take risks to potentially win better rewards when playing games, according to a new study.

“This is the first evidence that monkeys, like people, have 'would-have, could-have, should-have' thoughts,” said Ben Hayden, a researcher at the Duke University Medical Center and lead author of the study published in the journal Science.

Hayden and his team trained the monkeys to associate a green square on a computer screen with a “high value” reward and other colors with “low value” treats.

The monkeys then played a game similar to the game show Lets Make a Deal where they had to choose between eight identical white squares. If they found the square which hid the green, they got a bigger serving of juice.

And to test if they were capable of the abstract thought process that allows humans to consider consequences and potential outcomes, they were shown what prizes they missed after receiving the juice.

The researchers monitored the neurons in an area of the monkey's brains called the anterior cingulate cortex, or ACC, which plays an important role in decision-making.

They found that the neurons responded in proportion to the value of the reward: the better the prize, the bigger the response.

They also found that the neurons responded in much the same way when the monkeys were shown what rewards they missed.

“It is significant to learn that the neurons have a dual role, because the monkey can only adapt his behavior when he gets information on both of those events, real and missed,” said senior author Michael Platt of Duke University. This function could serve the purpose of helping monkeys make better choices in the future.

“These findings are consistent with the idea that the ACC represents both real and fictive reward outcomes to dynamically guide changes in behavior,” the study concluded.

“Such a mechanism may be crucial in complex social environments, where the behavior of others provides a rich supply of fictive information.”

To measure how this brain function might help monkeys learn, the researchers kept the green square in the same position or moved it to the next position most of the time.

The monkeys appeared to be able to adapt to the pattern because they chose those targets significantly more often than what would have happened by chance.

They were also more likely to select a target that was not among the most frequent positions if it had offered a large reward on the previous trial and the monkey had missed it.