Clap If You Believe in the Tinkerbell Effect

The Tinkerbell Effect spans multiple scientific disciplines, including economics, but perhaps its most dramatic demonstration is in psychology - where it literally makes people see things.

There are multiple Tinkerbell Effects, but they all get their name from the scene in the stage play of Peter Pan during which Tinkerbell is dying and the audience is told to clap if they believe in fairies. Perhaps there has been an audience that failed to clap (and I would love to know if the actors prepare for such a thing), but generally they clap, and Tinkerbell springs back to life. If people believe something, it will occur.

In psychology, it just makes people believe that something they believe in will occur. This happens a lot. One study in particular, told people to estimate the speed of gray dots moving across a black background. The dots were on a screen - a split screen. The other side of the screen had another field of gray dots, which the person doing the estimating controls. With the push of a button, they can speed up the pattern, or slow it down, until it matches the dots on the other side of the screen.

Forty percent of the time, the dots on the other side of the screen weren't moving. Twelve out of the fifteen volunteers still felt they were able to "match" the speed in all cases. One of the remaining three couldn't see the dots move, whether they were moving or not.

The Tinkerbell Effect works in a lot of different experimental situations. People believe that they can, with the push of a button, make a random flashing of lights into a coherent pattern, even though the button does nothing. In one case, a group of people were put in a room and told to concentrate on making the lights on a circular displace move counterclockwise. They thought they did. What they didn't know is that they were in the same room as a group of people who were told to make the lights move clockwise and also thought they did.

Sometimes what we think determines what we see.

[Via The Tinkerbell Effect: Motion Perception and Illusion, The Drunkard's Walk.]