The effect of irrelevant spatial correspondences on two-choice response-time.

Simon and his associates have demonstrated a general effect in two-choice reaction- time tasks involving laterally disposed responses, and a succession of stimuli presented unpredictably at either of two laterally disposed positions, the stimulus positions being irrelevant in deciding the response. Reaction times are found to be faster for trials in which the spatial loci of stimulus and response correspond than for trials in which they counter-correspond. The present experiment investigated the dependence of this effect upon spatial orientation and upon the logical character of the task. The effect was found not only for laterally disposed pairs of stimulus positions and responses but also for vertical dispositions. The effect was found to be critically dependent upon the logical character of the task, such that it could readily be produced in a reversed form. The results could be well described by considering the logical characters of the recodings of the relevant and irrelevant attributes of stimulus and response. The special status formerly attributed to the processing of spatial information is questioned.