Monkeys with human-like hands are more likely to fall for a simple magic trick than primates without opposable thumbs.
New research published in Current Biology has revealed these differences demonstrate how monkeys’ own physical capabilities heavily influence their perception and prediction of others’ movements.
Trained magician Elias Garcia-Pelegrin showed how animals’ perceptive systems can easily be tricked.
Garcia-Pelegrin performed an illusion for three species of New World monkeys including Humboldt’s squirrel monkeys, common marmosets and yellow-breasted capuchins.
The monkeys were trained to watch the magician handle an item of food and select which of his closed fists had the reward.
Then the magician showed the primates the food with one hand before he either passed it to the other or performed a trick called the French drop.
The French drop involves pretending to pass an object from one hand to another by gripping it between thumb and forefingers.
Both the capuchins and squirrel monkeys correctly chose the hand with the food when a real transfer happened but were fooled by the illusion.
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Marmosets, which lack opposable thumbs, didn’t fall for the French drop but were fooled when the reward was transferred to the other hand.
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“This exemplifies how our internal biases about movements can be sometimes misleading, and we seem to share this with other primates as well,” Garcia-Pelegrin said.
“This is what magicians seem to capitalise on by exhibiting these cues but changing the movement’s outcome.
“Magicians can trick us and it appears that monkeys can be fooled as well.”
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