Magic trick only fools monkeys with opposable thumbs, study suggests

New research shows that the magic of sleight of hand often only captivates silly monkeys with opposable thumbs to humans – a trait shared with humans.

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Scientists performed a famous magic trick for three species of monkeys with different hand structures – capuchins, squirrel monkeys and marmosets.

He found that in order to perform the trick, a magician needed to have the same anatomy as his audience.

Psychologists used a sleight-of-hand trick called the French drop, in which an object disappears when a bystander assumes it is taken from one hand with the hidden thumb of the other hand.

Magicians use complex techniques to mislead the observer into experiencing the impossible. It’s a great way to study blind spots in meditation and perception

Dr. Elias Garcia-Pellegrin

The French Drop is one of the first tricks any budding magician must master.

A coin is displayed in one hand, and the other hand reaches up and grabs it. The palm of the other hand is facing inward, with the magician’s thumb hidden behind the fingers.

The spectators know that the thumb is hidden – ready to hold – so the coin is assumed to have been taken when it is not visible. His attention follows the other hand, only to find it empty when it appears.

The magician secretly drops the coin into the palm of the original hand.

The study, conducted at the University of Cambridge’s Laboratory of Comparative Cognition, found that monkeys lacking opposable thumbs did not fall for the trick and remained at a location of tasty treats trying to make a magician disappear.

According to the researchers, sharing a biomechanical ability may be necessary to accurately predict the movements of those same organs in other individuals.

Elias García-Pellegrin, who has practiced magic for a decade – and conducted experimental work during his PhD at Cambridge, said: “Magicians use complex techniques to trick the observer into experiencing the impossible It’s a great way to study blind spots in meditation and awareness.

“By examining how species of primates experience magic, we can understand more about the evolutionary roots of the cognitive deficits that expose us to the cunning of magicians.

“In this case, whether having the manual ability to produce an action, such as grasping an object between a finger and thumb, is necessary for predicting the effects of that action in others.”

In the experiment, morsels of food for the monkeys replaced coins, and were given as prizes – but only if the animals guessed the correct hand.

The trick was performed repeatedly on 24 monkeys—eight capuchins were dazzled with peanuts, eight squirrel monkeys with dry mealworms, and eight marmosets with marshmallows.

Capuchins, who have opposable thumbs and are renowned for dexterity – using stone tools to crack nuts in the wild, were routinely fooled by the trick (81% of the time).

Squirrel monkeys are less dexterous than capuchins, with limited thumb rotation, but can oppose their thumbs.

Experts say that they cannot make the same precise grip as capuchins and humans.

Yet the squirrel monkeys were regularly misled by the missing mealworms (93% of the time).

“Squirrel monkeys couldn’t make absolute precision grasps, but they were still fools. This suggests that a monkey doesn’t need to be expert in a movement to predict it, just being able to do so roughly, ” Doctor. said Garcia-Pellegrin, recently appointed an assistant professor at the National University of Singapore.

The study found that marmosets do not have opposable thumbs, and are rarely taken by magic (only 6% of the time).

They simply chose the hand the marshmallow was initially placed in, and stuck with it.

The team tried to minimize the trick by actually completing the hand-to-hand transfer instead of misdirecting with the French drop.

This time, the Capuchins and Squirrel Monkeys guessed correctly and put out the food, and the Marmosets missed.

Finally, the scientists created their own version of the French drop, which they call the “Power Drop”.

It uses a hand action that all monkey species can do – essentially a full fist grab. Power Drop fooled all species of monkeys most of the time.

The study is published today in the journal Current Biology.