Scientists Uncover Why Picture Perception Works

When you look at a picture, there is only one viewing position--thepicture's center of projection--that yields a correct image at youreye. For example, there's but one place in the movie theater where thefilm creates the same image at your eye as the original scene. Viewingfrom other places causes distortion of the image at your eye. Why,then, don't moviegoers rush to the correct position? Indeed, do theyeven know where that position is?

Martin S. Banks, Professor of Optometry and Vision Science atthe University of California at Berkeley, Dhanraj Vishwanath, AssistantProfessor of Psychology at Rochester Institute of Technology, and AhnaGirshick, a Ph.D. student at UC Berkeley, have developed a newscientific model of the processes underlying the phenomena. Theirresults will be presented in the upcoming edition of NatureNeuroscience.

"If the brain processed pictures in the same way it did realobjects, you should actually see things in the picture change anddistort for every different location you view it from," Banks says."The human visual system automatically corrects such distortions, butresearchers have not been able to pinpoint how this correction occurs."

Using a series of psychophysical experiments, Vishwanath,Girshick and Banks were able to show that the human visual systemflexibly adjusts to viewing position such that sitting at the rightplace isn't required. The brain makes small adjustments to the imagethe eyes receive, such that the picture appears the way it is supposedto--even when you look at it from different locations. The work hasimplications for designing better devices that display 3D pictures, andalso for creating more realistic computer-graphic images. It will alsoincrease our understanding of how the eyes and brain work, providinginsight for both medical and psychological use.

"Visual perception of displayed images is a key factor inhuman decision making," Vishwanath notes, "Properly describing howhumans view and perceive images will provide a better understanding ofwhy people respond positively to some images and negatively to others."

The full results of the study can be viewed on the Nature Neuroscience Web site at http://www.nature.com/neuro.