ATTENTIONAL DISTRIBUTION IN THE VISUAL-FIELD DURING SAME-DIFFERENT JUDGMENTS AS ASSESSED BY RESPONSE COMPETITION

Judgments of same and different on a comparison task have been found t o be subject to response competition if an irrelevant stimulus is pres ented in the display along with the target stimuli. For example, the r eaction time for judging two letters the same is markedly increased if a different but irrelevant letter is also present in the display (C. W. Eriksen, O'Hara, & B. [A.] Eriksen, 1982). We have made use of this competition effect to map the visual attentional field in two dimensi ons. In two experiments, we varied the size of the attended area by va rying the separation of the comparison stimuli. The boundaries of the attended area were mapped by varying the location of a response-compet itive irrelevant noise letter. On this task, the attended area was fou nd to be elliptical in shape, with the location of the target stimuli defining the major axis. The minor axis of the ellipse increased in di rect proportion to increases in the major axis. Rather than interpret these field effects in terms of areas of enhanced processing, we propo se that instead they represent the limits or failures in inhibition of competing stimulation.