MOTION TRAJECTORY ILLUSION AND EYE-MOVEMENTS

We describe a visual illusion where a moving target produces an illusi onary trajectory. Previously it has been suggested that this illusion is related to eye movements, but the exact nature of the relation, as well as relevant stimulus conditions and eye movement type were unknow n. In two experiments, we varied critical stimulus conditions, recorde d eye movements and judgments of trajectories. In Experiment 1, a visu al cue led to a reduction of the illusion, however, only if a saccadic eye movements preceded the target's change of direction within a crit ical interval. assessed by SacOA (Saccadic Onset Asynchrony). In Exper iment 2, an analogous result was found under conditions of sudden velo city changes. The results are explained by;critical timing between smo oth pursuit and different phases of saccadic eye movements.