Expectation

The Hering illusion is an optical illusion discovered by the German physiologist Ewald Hering in 1861. The two lines are both straight, but they look as if they were bowing outwards. The distortion is produced by the lined pattern on the background, that simulates a perspective design, and creates a false impression of depth.

The Hering illusion looks like bike spokes around a central point, with lines on either side of this central, so called vanishing point. The illusion tricks us into thinking we are moving forward. Since we aren’t actually moving and the figure is static, we misperceive the straight lines as curved ones.

Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York says optical illusions are due to a neural lag which most humans experience while awake. When light hits the retina, about one tenth of a second goes by before the brain translates the signal into a visual perception of the world. Scientists have known of the lag, yet they have debated over how humans compensate, with some proposing that our motor system somehow modifies our movements to offset the delay.

Changizi asserts that the human visual system has evolved to compensate for neural delays, generating images of what will occur one tenth of a second into the future. This foresight enables human to react to events in present. This allows humans to perform reflexive acts like catching a fly ball and to maneuver smoothly through a crowd. Illusions occur when our brains attempt to perceive the future, and those perceptions don’t match reality. The Hering illusion tricks us into thinking we are moving forward, and thus, switches on our future seeing abilities. Since we aren’t actually moving and the figure is static, we misperceive the straight lines as curved ones.

Chnagizi says, “Evolution has seen to it that geometric drawings like this elicit in us premonitions of the near future. The converging lines toward a vanishing point are cues that trick our brains into thinking we are moving forward as we would in the real world, where the pair of lines seems to bow out as we move through it, and we try to perceive what that world will look like in the next instant.”


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