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Visual Cognition: The role of eye movements in real world scene perception


If you could follow your eye movements as you looked at the scene on the left, you might be surprised find that your eyes do not move smoothly or continuously over the picture. To see this, simply have a friend read a book or look at a picture and watch their eyes.  You will see your friend make a series of fixations (in which the eyes pause for just a fraction of a second) and saccades (fast, ballistic movements from one fixation to the next).  Below is a hypothetical scan path in red of fixations and saccades.  Typically, people make 2-3 fixations each second! 

The reason we must move our eyes is that the real processing power of the eye is contained in a very small region of the retina known as the fovea.  It is here that color and detail are processed.  However, only a tiny portion of the all the information on the retina is imaged on the fovea.  Therefore, in order to "see" the entire scene, you must direct your eyes towards various parts of the scene.  How our visual-perceptual system creates a rich and continuous visual experience from a sequence of fixations and saccades is one the most intriguing questions today in cognitive-visual psychology.