Planning keypress and reaching responses: effects of response location and number of potential effectors.

In previous work the authors argued that the potential number of effectors in the response set is crucial in discriminating (multiple-effector) keypress from (single-effector) reaching responses. It is not clear, however, what influence the locus of responding (on vs. off the stimulus location for reaching and keypressing, respectively) has on reaction time (RT) performance. In 3 experiments, the authors systematically manipulated response location and response type using a spatial precuing task. The results consistently showed that even though response location did influence the RTs of keypress and reaching responses, the effect of the number of potential effectors was dominant in shaping the prototypical RT profiles of the 2 response types. These outcomes underscore the importance of the anatomical identity, in addition to response location, in response coding and corroborate the notion that distinct mechanisms dominate performance in single- and multiple-effector visuomotor tasks.