The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

Studied the effects of variations in stimulus quality and response complexity on P300 latencies and lateralized readiness potential (LRP), to relate individual evoked potentials to specific stages of processing. 18 college students made a left or right hand response upon presentation of digits surrounded by a dot pattern. Ss received feedback on the mean and variability of reaction time (RT) and the number of errors, and EEGs were recorded. Results show that the 2 tasks had additive effects on RT. Variations in stimulus degradation influenced the latencies of both components, while alterations in response complexity had no effect on the P300 latency. The onset latency of LRP remained unchanged across levels of response complexity. Findings support the notion of temporal selectivity of stage manipulations, and refine the functional interpretation of LRP.