The Science of Illusion

The New York Times:

PINCH a coin at its edge between the thumb and first fingers of your right hand and begin to place it in your left palm, without letting go. Begin to close the fingers of the left hand. The instant the coin is out of sight, extend the last three digits of your right hand and secretly retract the coin. Make a fist with your left — as if holding the coin — as your right hand palms the coin and drops to the side.

You’ve just performed what magicians call a retention vanish: a false transfer that exploits a lag in the brain’s perception of motion, called persistence of vision. When done right, the spectator will actually see the coin in the left palm for a split second after the hands separate.

This bizarre afterimage results from the fact that visual neurons don’t stop firing once a given stimulus (here, the coin) is no longer present. As a result, our perception of reality lags behind reality by about one one-hundredth of a second.

Magicians have long used such cognitive biases to their advantage, and in recent years scientists have been following in their footsteps, borrowing techniques from the conjurer’s playbook in an effort not to mystify people but to study them. Magic may seem an unlikely tool, but it’s already yielded several widely cited results. Consider the work on choice blindness — people’s lack of awareness when evaluating the results of their decisions.

Read the whole story: The New York Times