The relative contributions of internal motor cues and external semantic cues to anticipatory smooth pursuit

Smooth pursuit eye movements anticipate the future motion of targets when future motion is either signaled by visual cues or inferred from past history. To study the effect of anticipation derived from movement planning, the eye pursued a cursor whose horizontal motion was controlled by the hand via a mouse. The direction of a critical turn was specified by a cue or was freely chosen. Information from planning to move the hand (which itself showed anticipatory effects) elicited anticipatory smooth eye movements, allowing the eye to track self-generated target motion with virtually no lag. Lags were present only when either visual cues or motor cues were removed. The results show that information derived from the planning of movement is as effective as visual cues in generating anticipatory eye movements. Eye movements in dynamic environments will be facilitated by collaborative anticipatory movements of hand and eye. Cues derived from movement planning may be particularly valuable in fast-paced human-computer interactions.