Just like humans, monkeys too display self-doubt and uncertainty, according to US-based scientists.
They found that macaques trained to play computer games will ‘pass’ rather than risk choosing the wrong answer in a brainteaser task, reports the BBC.
Prof John David Smith from the State University of New York at Buffalo and Michael Beran from the Georgia State University, trained the macaques, which are Old World monkeys, to use a joystick-based computer game.
The animals were trained to judge the density of a pixel box that appeared at the top of the screen as either sparse or dense. To give their answer, the monkeys simply moved a cursor towards a letter S or a letter D.
When the animals chose the correct letter, they were rewarded with an edible treat. There was no punishment for choosing the wrong answer, but the game briefly paused, taking away - for a few seconds - the opportunity for the animals to win another treat.
But the monkeys had a third option - choosing a question mark - which skipped the trial and moved on to the next one. This meant no treat, but it also meant no pause in the game.
The researchers saw that the macaques used this option in exactly the same way as human participants who reported that they found a trial too tricky to answer - they chose to ‘pass’ and move on.
“Monkeys apparently appreciate when they are likely to make an error. They seem to know when they don't know,” Smith told the BBC.
In the same trial, capuchins, which belong to the group known as New World monkeys, failed to take this third option.
“There is a big theoretical question at stake here: Did [this type of cognition] develop only once in one line of the primates - emerging only in the line of Old World primates leading to apes and humans?” explained Smith.
He said that the capacity think in this way was “one of the most important facets of humans’ reflective mind, central to every aspect of our comprehension and learning”.
“These results could help explain why self-awareness is such an important part of our cognitive makeup and from whence it came,” he added.