The P_D Reflects Selection of Nontarget Locations, Not Distractor Suppression

In visual search tasks, negative features provide information about stimuli that can be excluded from search. It has been shown that these negative features help participants to locate the target, possibly by attentional suppression of stimuli sharing the negative feature. Attentional suppression is assumed to be reflected in an event-related potential, the P-D component. To provide a further test of these assumptions, we presented the color of the distractor at the start of a trial and asked participants to find the other colored stimulus in the subsequent search display. Consistent with attentional suppression, we observed a P-D to a lateral distractor shown with a vertical target. However, the P-D occurred in this condition only when target and distractor could also be on opposite sides of fixation. The effect of trial context on the P-D suggests that the P-D reflects a search strategy whereby participants select stimuli opposite to the distractor when trials with opposite placements occur during the experiment. Therefore, the P-D to the distractor may in fact be an N2pc to the opposite stimulus, indicating that the distractor is not suppressed, but avoided by redirecting attentional selection to the opposite side.