Inhibition of irrelevant response codes is affected by matching target-distractor modalities.

Lateralized responses to central targets are facilitated when distractors are presented ipsilaterally (congruent trials) compared with contralaterally (incongruent trials) to the response. This accessory Simon effect is explained by assuming that distractors generate a spatial code that conforms to, or conflicts with, the response. The effect typically diminishes as the distractor-target interval increases. However, it is unclear whether irrelevant spatial codes passively decay or are actively inhibited. Given that inhibition takes time to develop, its operation may reverse the Simon effect-indicated by impaired performance in congruent compared with incongruent trials-when the distractor is presented prior to the target. In the present study, the temporal separation between distractor and target was systematically manipulated. Participants responded to a centrally presented visual (Experiments 1 and 2) or auditory (Experiments 3 and 4) target. A lateralized auditory distractor either occurred prior to, or simultaneously with, the target. A Simon effect occurred when distractor and target were presented simultaneously or in close temporal proximity. The effect was reversed with longer distractor-target intervals, but only when targets and distractors were presented in the same modality (Experiments 3 and 4), suggesting that an inhibition process operates on distractor events, which is stronger in the case of matching target and distractor modalities. (PsycINFO Database Record (c) 2019 APA, all rights reserved).