A metric for thought: a comparison of P300 latency and reaction time.

We confirm that the latency of the P300 component of the human event-related potential is determined by processes involved in stimulus evaluation and categorization and is relatively independent of response selection and execution. Stimulus discriminability and stimulus-response compatibility were manipulated independently in an "additive-factors" design. Choice reaction time and P300 latency were obtained simultaneously for each trial. Although reaction time was affected by both discriminability and stimulus-response compatibility, P300 latency was affected only by stimulus discriminability.