![]() ![]() ![]() This suggests that a monkey doesn't have to be expert in a movement in order to predict it, just roughly able to do it," said Garcia-Pelegrin. "Squirrel monkeys cannot do full precision grips, but they were still fooled. Yet squirrel monkeys were routinely misled by mealworms that seemingly vanished (fooled 93% of the time). However, they cannot perform a 'precision grip' in the same way as capuchins and humans. As such, they are still familiar with a hidden thumb interacting with fingers. Squirrel monkeys are much less dextrous than capuchins, with limited thumb rotation, but can oppose their thumbs. They mostly chose the empty second hand, and experienced a paucity of peanuts as a result. The capuchins were regularly fooled by the French drop (81% of the time). They can waggle each finger, and have opposable thumbs allowing "precision grip" between thumb and forefingers. Eight capuchins were dazzled with peanuts, eight squirrel monkeys with dried mealworms, and eight marmosets with marshmallows.Ĭapuchins are famed for dexterity, and use stone tools to crack nuts in the wild. They repeatedly performed the French drop on 24 monkeys. Scientists predicted that monkeys with opposable thumbs would act like human audiences: assume the hidden thumb had grabbed the item, and choose the wrong hand. Their attention follows the second hand, only to find it empty at "the reveal." The magician had secretly dropped the coin into the palm of the original hand.įood morsels replaced coins for the monkeys, and were given as rewards - but only if the animals guessed the correct hand. The audience knows the thumb is lurking - ready to grip - so assumes the coin has been taken when it is no longer visible. ![]() The palm of the second hand faces inwards, with the magician's thumb concealed behind fingers. The other hand reaches over and grabs it. The French drop is often the first trick any budding magician sets out to master.Ī coin is displayed in one hand. "In this case, whether having the manual capability to produce an action, such as holding an item between finger and thumb, is necessary for predicting the effects of that action in others," said Garcia-Pelegrin, recently appointed an assistant professor at the National University of Singapore. "By investigating how species of primates experience magic, we can understand more about the evolutionary roots of cognitive shortcomings that leave us exposed to the cunning of magicians." It is a great way to study blind spots in attention and perception," said Dr Elias Garcia-Pelegrin, who has practiced magic for a decade, and conducted the experimental work during his PhD at Cambridge. "Magicians use intricate techniques to mislead the observer into experiencing the impossible. The study is published today in the journal Current Biology. This is true even when those apparently accurate predictions end in befuddlement at the hands of an illusionist. The research suggest that sharing a biomechanical ability may be necessary for accurately anticipating the movements of those same limbs in other individuals. The study, carried out at the University of Cambridge's Comparative Cognition Lab, found that monkeys lacking opposable thumbs did not fall for the assumption - staying wise to the whereabouts of tasty treats a magician tried to make disappear. Psychologists used a sleight-of-hand trick called the French drop, in which an object appears to vanish when a spectator assumes it is taken from one hand by the hidden thumb of the other hand.
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