Like humans, monkeys too learn from their mistakes

Washington, May 15 (ANI): Just like humans, monkeys have the ability to recognise missed opportunities and learn from their mistakes, says a new research.

"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.

Hayden and colleagues watched individual neurons in a region of the brain called the anterior cingulate cortex (ACC) that monitors the consequences of actions and mediates resulting changes in behaviour. 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 colour 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 colour green and the low-value rewards with other colours. After receiving a reward, the monkey was also shown the prizes he missed.

The researchers found that neurons in the ACC responded in proportion to the reward -- a greater reward caused a higher response.

They also found that these same neurons responded when monkeys saw what they missed. Most of these ACC neurons responded the same way to a real or imagined reward.

To measure how these responses might help the monkey to learn, the researchers kept the high reward in the same position 60 percent of the time, or moved it one position clockwise, so that a monkey could possibly notice and adapt to that pattern.

The monkeys chose targets next to potential high-value targets more often than those next to low-value targets, which suggested that they understood the relationship between the high value target on the current trial and its likely location on the next trial. The monkeys learned the pattern and chose the high value more often than by a chance.

Michael Platt, Duke professor of neurobiology and evolutionary anthropology and senior author of the study, said: "It is significant to learn that the neurons have a dual role, because the monkey can only adapt his behaviour when he gets information on both of those events, real and missed."

People are much more likely to gamble if they see they could have won big by gambling in the past. Thus, the researchers hypothesized that the monkeys would also select the target if it had offered a large reward on the previous trial and the monkey had missed it, and indeed, they observed this pattern.

The researchers noted that the effect might have reflected an increased willingness to switch to a new target, because the likelihood of switching increased with larger missed rewards.

"This was not merely a function of the high-value targets holding a positive association for the monkey," Platt said.

Platt said that the monkeys' ACC neurons signalled missed reward information, and used a coding scheme in the brain that was similar to the coding used to signal real outcomes.

The researchers suspect that these neurons actually helped the monkeys to make better choices in the future.

The study is published in the journal Science. (ANI)