Humans Remember Motion Of Rotating Objects Poorly -- Inability May Have Evolutionary Roots

In multiple experiments, psychologist David Gilden, Ph.D. and his then graduate student Christy Price of the University of Texas at Austin, showed 48 undergraduate students computer driven objects that either moved right or left across the screen or rotated clockwise or counterclockwise, or grew larger or smaller, mimicking the way objects look when they move toward or away from you. During the first phase of the experiment, the students studied the objects as they moved on the screen. The researchers then showed them the same objects either moving as they had previously or in a new direction or with a different motion.

After several experiments, Gilden and Price found that study participants could accurately recall five minutes later the direction of the motion of both looming (movement toward or away from you) and translating (movement from one point to another) objects but they only performed at chance when trying to remember the direction of rotating objects.

This is particularly curious because looming motion and rotating objects both project fairly complicated patterns of movement on the retina. Looming motions seem to be as complicated visually as rotations and seem also to be processed in the same area of the brain. So, if the complexity of the image on the retina predicts cognitive function, people's memory for looming motion would be approximately equal to their memory for rotating motion. Dr. Gilden's current experiments however prove that it is not.

Why are human beings so poor at remembering the direction of rotating objects? Dr. Gilden theorizes that being able to judge a looming or translating object had consequences for people throughout our evolution. It was critical, for example, to know whether the animal you were hunting was coming at you or retreating. But, there were no similar instances that made a memory mechanism for rotating objects important.

"Apparently," Dr. Gilden concludes, "visual understandings are not organized in terms of the complexity of what is on the retina, but rather in terms of what the practical consequences are for behavior. When it comes to motion, humans are much more concerned with where things are going than with their orientation."

Therefore, Gilden concludes that the best way to teach people to pull a car out of a spin is to teach them rote rules for doing so because we do not remember enough about rotations to be able to control the spinning car based on past experiences. Dr. Gilden plans to continue to research people's inability to remember rotating motion and wants to try to find the point in the visual system where rotating movement is dropped rather then being passed unto higher cognitive and memory regions of the brain. He believes that because rotations held no evolutionary significance for us, the brain simply developed to ignore them at highly cognitive levels.