Department of Psychology
It has been known since the classical work of Dodge (1930) and Westheimer (1954) that smooth pursuit eye movements anticipate the future direction of motion of targets. Anticipation in smooth pursuit is somewhat surprising because pursuit is traditionally viewed as a reactive process that acts to compensate for the motion of the target across the retina. Prior attempts to account for anticipatory pursuit have emphasized either rote learning of the motion path, associative learning, or short-term extrapolation of the motion. I will describe results of several experiments showing that anticipatory smooth eye movements can be evoked by visual cues, or by knowledge of the past history of motion (in the absence of overt cues), or by one’s own intentions to alter the path of target motion. Cues that illustrate the motion path by virtue of their perceptual structure are far more effective than cues that are arbitrarily linked to the motion path, or beliefs derived from simply telling the pursuer about the future motion path. Taken together (and considering the intriguing patterns of anticipatory pursuit movements found in other species), these results suggest that prediction is as fundamental to smooth pursuit as it is to the operation of many other visuo-motor behaviors. The pursuit system appears to be organized so as to take advantage of any source of information that allows future motion to be predicted with a reasonably high level of confidence.