Barcelona doctor Elías García-Pelegrín has managed to combine his two greatest obsessions in his research profession: magic and animal cognition. According to him, the dichotomy between art and science makes little sense. Artists try to study the human condition just like psychologists and biologists, except the latter use the empirical method.
Magicians, in particular, need to understand human perception and attention in order to fool their audience. His magic tricks can give us a lot of information about our consciousness and perception of reality. García-Pelegrín is currently Professor of Animal Behavior at the National University of Singapore and is interested in using magic to understand how other animals perceive the world.
He recently published a curious study he conducted while doing his PhD at the University of Cambridge, proving that monkeys, like us, can also be fooled by magic tricks. Of course, only if they share the magician’s motor skills, i.e. can perform the same movements as the magician.
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For the studio procedure, he performed one of the first tricks every magician learns: the French Drop. With the left hand, the magician shows a coin, while with his other outstretched hand, he stretches out and hides the thumb behind the fingers. However, the human audience knows that there is a thumb ready to grab the coin once it is no longer visible. The surprise comes when the magician separates the two hands, opens them and the coin remains in the original.
In this case, García-Pelegrín performed the trick in front of a slightly different crowd. The subjects of his study were 24 monkeys of three different species: eight capuchin monkeys, eight spider monkeys and eight marmosets. Instead of a coin, he used a small piece of food. If the monkeys guessed which hand it was in, they kept it.
The choice of the three types was no coincidence. Capuchins are known for their great craftsmanship. The physiognomy of their hand allows them to control each finger individually and perform a precise grip between thumb and forefinger. With these skilled hands, they routinely use stone tools to crack nuts in the wild. In the experiment, capuchin monkeys fell into the French release trap 81% of the time. The trick had a similar effect on them as it did on human audiences.
Spider monkeys are less agile than capuchin monkeys. The rotation of their thumb is limited, but they can still resist that finger to some degree to touch the index finger. In rare cases, they have also been observed using rudimentary tools. Like the Capuchins, they were deceived at a rate of 93%.
Finally, marmosets differ from the previous two in that they do not have opposable thumbs and cannot perform a precision grip. They are very small primates whose hands have evolved to climb vertical trunks. In this regard, they find it more useful to spread all five fingers evenly to increase surface area while digging in all nails. Oddly enough, the magic trick didn’t work for them, as 6% of the time they just chose the hand that was supposed to make the hold.
thumb or brain?
It could be that this different result is not due to differences in the monkeys’ hands, but to other factors such as body size or cognitive abilities. Because of this, researchers invented a new version of the French Drop, which they dubbed the “Power Drop.” The trick is the same, except that instead of using a precise grip with the thumb, the grip is done with the fist, flexing the rest of the fingers.
In this case, the common marmosets fell for the magic trick, as did capuchins and spider monkeys. The gesture the magician makes in this trick is certainly familiar to the common marmosets, as they regularly use it to catch food. The difference between the two tricks is very subtle, but appears to have radically different effects on the common marmoset brain.
García-Pelegrín, in turn, conducted the French fall under the watchful eye of a jay that doesn’t even have hands in a previous study. As with the marmosets, the deception didn’t work. What can be the reason? Why do the tricks only work if the viewer knows the magician’s gestures from experience?
The magic of mirror neurons
The answer could be found in the so-called “mirror neurons”. Neuroscience has provided ample evidence that the same motor neurons that activate when we perform an action also do so when we see another person perform the same movements.
For example, when we watch a dog eat, the neurons responsible for our jaw movements go to work. However, they are not activated when we see dogs barking because this action is not present in our motor repertoire.
Some scientists like Guiacomo Rizzolatti, discoverer of mirror neurons, have suggested that thanks to them we can interpret the purpose of other people’s actions. That is, we understand the actions of others when they make our motor neurons vibrate. Therefore, it would be more difficult for animals to decipher the movements that we cannot perform.
Of course, the García-Pelegrín study provides irrefutable evidence that a person’s motor skills influence how they perceive and interpret the movements of others. In the French trap trick, the common marmosets didn’t think the magician was grasping the coin with his thumb, despite being familiar with human hands. It’s possible that because they didn’t have this ability, their motor neurons weren’t activated and therefore they couldn’t interpret the movement.
However, these are only hypotheses, since the function of mirror neurons is still a matter of scientific debate. There is still much to be done before we fully understand how animals perceive and process the actions of others. Maybe science just needs to put some more magic into their investigations.
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