Most humans do not have the power to predict the future, but we can see it. At least we can see one-tenth of a second of it. The May-June issue of the journal Cognitive Science published a review by Mark Changizi of Rensselaer Polytechnic Institute, claiming that the human visual system has evolved to allow us to see fractions of a second into the future.

When light hits our retina, it takes approximately 100 milliseconds, or one-tenth of one second, for our brain to perceive an image. While it seems insignificant, the delay is consequential when dealing with moving objects. Changizi uses the examples of walking through a crowd or catching a ball to illustrate the significance: A person moving at a slow walk can move at least 10 centimeters forward in one-tenth of one second. A ball passing one meter away from you, traveling at one meter per second, moves six degrees from where you perceive it, in one-tenth of a second. We must anticipate and compensate for these delays in perception, or humans would constantly be running into each other, and we could never play baseball.

Many scientists and theorists have hypothesized that humans’ motor systems compensate for this delay in visual processing by adjusting our movements. Changizi, however, theorizes that it is the visual system that compensates for the delay, effectively generating images of what will occur one-tenth of a second into the future. This way, we are able to continually view the world in the present, rather than seeing what happened one-tenth of a second ago. His theory is called “perceiving the present.”

The same ability, he explains, is what allows our brains to be tricked by optical illusions. Many geometric illusions trick our mind into thinking we are moving forward. Changizi explains that the illusions occur when our brains attempt to perceive the future, but the perceptions do not match reality. There are four main types of misperception: size, speed, contrast, and perceived distance. Optical illusions affect one or more of these misperceptions.

Based on these hypotheses, Changizi was able to arrange more than 50 types of optical illusions into 28 classes, organized in a 7 x 4 matrix. This classification is able to predict how variables, such as size or distance from a center point, will affect perception. Other scientists have tried to explain one or two illusions, but no one has been able to devise a unified theory to explain this many illusions.

This new evolutionary theory about the visual system may have applications in enhancing visual displays or art, but it may also help scientists to explain the mechanisms of our visual system.

Reference

Changizi, M., Hsieh, A., Nijhawan, R., Kanai, R., Shimojo, S. (2008). Perceiving the Present and a Systematization of Illusions. Cognitive Science: A Multidisciplinary Journal, 32(3), 459-503. DOI: 10.1080/03640210802035191

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