A responding hand effect in a simple-RT precueing experiment: evidence for a late locus of facilitation

Reaction time (RT) to a peripheral flash target is often shortened by a shortly leading (about 100 msec) non-informative cue presented at the same location; later on (500 msec), to the contrary, RT is lengthened. In this paper, an interaction between target position and responding hand is reported. Subjects made speeded key-press responses to targets presented either 7 degrees to the left or 7 degrees to the right of fixation. A valid (same location) or invalid (mirror-symmetric location) cue preceded the target by either 80 or 500 msec. Depending on the trial, subjects used either the left or the right hand. The crossover in RT, from facilitation to inhibition, is observed only when the target is on the same side as the responding hand. An analysis of the RT distributions suggests that (a) facilitation is due to decision rather than perceptual processes, (b) inhibition is due to motoric processes.