THE GAP EFFECT FOR EYE AND HAND MOVEMENTS

A temporal gap between fixation point offset and stimulus onset typica lly yields shorter saccadic latencies to the stimulus than if the fixa tion stimulus remained on. Several researchers have explored the exten t to which this gap also reduces latencies of other responses but have failed to find a gap effect isolated from general warning effects. Ex periment 1, however, showed a robust gap effect for aimed hand movemen ts (which required determination of a precise spatial location), regar dless of whether the hand moved alone or was accompanied by a saccadic eye movement. Experiment 2 replicated this aimed hand gap effect and also showed a smaller effect for choice manual keypress responses (whi ch required determination of the direction of response only). Experime nt 3 showed no gap effect for simple manual keypress responses (which required no spatial determination). The results are consistent with an interpretation of the gap effect in terms of facilitation of spatiall y oriented responses.