The impact of response congruence on speech production: An event-related potentials study

A puzzling finding in the speech production literature is the facilitation of categorically related distractors in a superordinate level naming task. The context is in this case response congruent, because application of the task instruction to the context would lead to the correct response. This study investigates the time-course of response congruence effects in speech production using event-related potentials (ERPs). Participants overtly named target words that were overlaid on context pictures with either their superordinate category level name or their associated function, while their response times and ERPs were recorded. Behavioural results replicate the facilitating effect of response congruence. The ERP results showed that the N2 was larger for a response incongruent than congruent context, and this effect correlated with the behavioural pattern of results. This key finding suggests that response incongruence is associated with a conflict-monitoring response which drives the behavioural effect. Further, N400 amplitude was not modulated by response congruence, showing that its effect appears confined to the conceptualisation phase. Finally, P3 modulations mirrored those in RTs, but unlike the N2 effect, they did not correlate with RTs. This suggests that, although the facilitating effect of response congruence is confined to the conceptualisation phase of speech production, response incongruent representations may remain active during later processing stages, or that this late effect of response congruence reflects conflict resolve. Implications for models of speech production are discussed.