Optical illusion
Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York thinks optical illusions are due to a 'neural lag'. 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, and have discussed how humans compensate for it. Some suggest that our motor system somehow modifies our movements to offset the delay.