Event-related potential measures of processing during an Implicit Association Test

This study recorded event-related potentials during the Implicit Association Test, a reaction time-based measure of implicit social attitudes. An N2, peaking at about 350 ms was larger in the incongruent condition, perhaps reflecting greater response monitoring. The latency to an initial late positive peak, P300, a measure of stimulus classification time, was not longer in the incongruent than the congruent condition. A later small amplitude positive peak was observed in the incongruent condition, but was not visible in the congruent condition. The additional positivity is consistent with the hypothesis that participants make an initial decision to determine whether a task set switch is required, and then make a subsequent decision about the correct response, perhaps resulting in delayed reaction times.