A magic trick that only fools the monkeys with an opposite thumb

How you move your body has a direct impact on how you interpret the movements of others – and therefore also whether or not you fall for a magic trick. This is shown in an experiment in which psychologists watched how three different species of monkeys interacted with a magic trick using the thumb and forefinger delicate grip, a typical human grip that none of the three species of monkey had ever mastered.

The magical experience will be described this week By a team of psychologists led by Elias García Pellegrin (National University of Singapore). Current Biology. Previously, this was a magical experience Even with crows Done, who don’t even have hands, but do almost everything with their mouths. So they were not deceived by the wizard’s crafty gestures. But if the experimenter based his deception only on speed, then the deception succeeded.

wrong hand

The species of monkeys that were (somewhat) capable of this precise grip (yellow-breasted capuchin monkeys and Humboldt squirrel monkeys) were fooled by the magic trick: They expected their food reward to be in the wrong hand, exactly according to the intent of the magic trick. But the species of monkeys that themselves were completely incapable of gripping the experimenter’s hidden hand (ordinary monkeys) did not allow themselves to be deceived by the sorceress, these monkeys simply grabbed the hand in which the food remained. But if the trick is performed with an electric grip, in which the body is held with all the fingers, just as the stick is held, then the monkey’s hand also falls into the experimenter’s sleight of hand. This is a way to keep this monkey that they use themselves.

The trick used is one of the most famous and simple in the magic repertoire, namely French licoricein which a coin (or for monkeys: a tasty snack) is shown in one hand between thumb and forefinger, after which it is held in the other hand It seems They are arrested and handcuffed. In fact, the coin (or morsel) is caught in the palm of the first hand. When the magician blows into the seconds hand and opens the fist, the object appears to have magically disappeared.

Smart move

Monkey researcher and professor of cognitive psychology Mariska Kret (University of Leiden) calls the research interesting, if only because there is still so little research on the effect of one’s own body on the perception of others. Crete: “So I think that comparing three species of primates with different thumbs is a smart move. However, it would have been better if they had examined at least one type of imprecise grip. Because maybe there is something else going on with those monkeys that is causing them to react differently.” Different from the other two major types!”

Crete also sees many opportunities for further research. “Are people born without hands susceptible to this magic trick? I suspect so, which would suggest it is innate.”

Crete says the broader context of the research is also important. “We are constantly busy predicting the world around us. For social animals, that world often consists of interactions with certain species and it is helpful to know what they are doing or are going to do.” And especially for humans, hands are extremely important in communication. Crete: “Our hands are usually free and we consciously and unconsciously make all kinds of gestures with them. When we notice others, we catch those gestures very quickly. I have shown in my own research that people can understand other people’s intentions during a match just by looking at arm and hand movements.”

A movie of researchers performing magic tricks.