Visual perception of movement patterns during smooth eye tracking.

A visual stimulus moving with constant velocity at a definite angle to the horizontal was presented during a 6.5% horizontal pursuit eye movement. The subjects were asked to report the direction of the stimulus movement under conditions of total darkness and on illuminated structured background. In both cases the subject's reports corresponded to the trajectory of the stimulus image on the retina rather than to the physical movement. In a second experiment the subjects were asked to localize the start and the end point of the stimulus motion on illuminated background. In this case the reports corresponded to the physical trajectory of the stimulus motion on the screen. The influence of the visual task on the perception of movement patterns during eye tracking is discussed.