Monkeys have regrets just like humans - at least when they're playing Deal or No Deal
By Fiona Macrae
15th May 2009
Wistful: A rhesus macaque
They are best known for making mischief.
But monkeys can feel regret too - at least when playing a version of Deal Or No Deal.
When given a task similar to the popular Channel 4 show, their brains registered missed opportunities, a study published in the journal Science reports.
Just as contestants on Deal Or No Deal wonder what might have been, the monkeys became wistful when realising their error.
Researcher Ben Hayden said: 'This is the first evidence that monkeys, like people, have " would-have, could-have, should-have" thoughts.'
Dr Hayden, of Duke University in the U.S., trained a group of rhesus macaques to play a game in which they were given a choice of eight white squares to pick from.
Underneath each square was a colour representing a prize, with green bringing the best reward - a sugary fruit juice.
After picking a square the monkeys were shown the prizes they had passed up.
When they learned they had missed out on the juice, they tried harder the next time.
Scans revealed what was happening inside the animals' brains. A region known to monitor the consequences of actions lit up during the game - the better the prize, the more active it was.
However, the same brain cells also sprang into action when the monkeys were shown what they had missed, suggesting they were computing what might have been.
In Deal Or No Deal, contestants are faced with a series of boxes holding specific amounts of money.
Players try to assess how much money is in their own box by opening the others, while being offered varying amounts of cash to take instead of the sum in their box.
Contestants gradually learn how much they could have won if they had guessed correctly, just as in the study the monkeys were shown what they had missed.
Wondering what might have been: Like contestants on Deal or No Deal, monkeys learned from their actions and tried harder to win the prize
Dr Hayden said: 'People are really good at thinking not only about why things have happened but what could have happened, how things could have turned out differently. As far as we knew only humans did this.
'Reasoning about abstract things is fundamental to forming a philosophical perspective so it is important to know whether this is something that distinguishes humans or is shared with other animals.'
Previous research has shown rhesus macaques can add up numbers with amazing accuracy. Faced with 40 addition problems, two scored nearly as well as students in their late teens and early 20s.