A magician performs a famous trick on monkeys but the real magic lies in their reaction!

New research shows that monkeys can be fooled more easily by a popular magic trick if they have opposable thumbs - revealing how our anatomy affects our ability to perceive the world around us.

"Our work raises the intriguing possibility that an individual's inherent physical ability strongly influences their perception and memory of what they think they have seen, and their ability to predict the hand movements of those around them," explains psychologist Nicola Clayton from the University of Cambridge in the UK.

Watching others perform a task can activate the same brain regions that light up if we were doing the task ourselves. This happens within our mirror neuron system, and the more familiar we are with a task, the more closely our brains mirror it.

Ballet dancers have stronger mirror neuron activation while watching ballet dances than during capoeira dances, for example. These actions are strongly encoded in our brains as a chain of cause and effect to provide the effort of anticipating common movements.

And magicians can exploit our reliance on this mental map to manipulate our perceptions. For example, if a magician shows you a coin in one hand, and makes moves to take it with the other, you would be forgiven for assuming that the coin passed from one hand to the other.

This is true even when the coin is blocked and the magician leaves the coin in the first hand.

As a practicing magician with a decade of experience, comparative psychologist Elias García-Pellegrin was curious to know whether the ability to personally perform a set of actions was necessary for mirror neurons to plot the same sequence of steps.

At the time of the study, Garcia Pellegrin, a researcher at the University of Cambridge, and a team of colleagues tested 24 monkeys representing three species. First, they showed the monkeys a favorite treat. They then pretended to transfer the treat in a 'French throw', or actually transferred it to the other hand.

Each test relied on a precise grip that included the thumb to move the item, regardless of whether the transfer was real or fake.

They also made some real transfers of the reward from one hand to the other.

Each test appears as if the magician is using a precision grip that includes a thumb to move the item, regardless of whether the transfer is real or fake.

Not all sleight-of-hand tricks require the use of the thumb. Although monkeys may not be able to perform the variations personally, there is nothing in their anatomy that prevents them from trying them.

In another round of testing, the researchers used a fist to grab (or pretend to grab) the item rather than a pincer grip, which seemed to fool the three types of monkeys most of the time.

"Squirrel monkeys can't do a fully accurate grasp, but they remain deceived," García-Pellegrin explains. "This suggests that the monkey does not have to be an expert on the movement in order to predict it, it is only able to do it approximately."

"There is growing evidence that the same parts of the nervous system that are used when we perform an action are also activated when we watch that action of others," says Clayton.

The psychologist goes on to say, "How one's fingers and thumb move helps shape the way we think, the assumptions we make about the world — as well as what other people might see, remember and expect, based on their expectations."

This research was published in Current Biology.