Electrophysiological signature of suppression of competitors during interference resolution

The electrophysiological evidence for suppression to date primarily draws upon traditional retrieval-induced forgetting and Think/No-Think paradigms, which involve strategic and intentional restriction of thought. Here event-related potential (ERP) signatures of suppression were examined using a novel task, which unlike traditional paradigms, does not include an initial priming step or intentional thought restraint. Participants were instructed to verbally generate semantically related responses to cue words (e.g., "PIZZA"), and unrelated responses to others. According to an inhibitory account of interference resolution, semantic competition from automatically activated target words must be resolved in order to generate an unrelated response, whereas no resolution is required for generating related responses. In a subsequent phase, accessibility for target words (e.g., "PEPPERONI") that required suppression, words that did not require suppression, as well as new control words was measured using a lexical decision task. We observed a sustained late positivity for unrelated responses in the generation task, and early negative amplitudes of suppressed items in the lexical decision task. These findings are consistent with inhibitory mechanisms operating at retrieval to suppress competitors and show that such processes operate on automatically activated items that are not presented in the context of an experiment, representative of retrieval situations that occur in everyday life.