ON THE UTILITY OF P3 LATENCY AS AN INDEX OF MENTAL CHRONOMETRY

The stimulus evaluation view on P3 latency holds that P3 latency mainl y reflects stimulus processing time, in contrast to response-processin g time. A review of the experimental evidence, however, leads to the c onclusion that P3 is not a sensitive tool for separating between stimu lus- and response-related processes. Rather, it appears that P3 latenc y is a sensitive index of any response-time changes when response time s in the fast condition are brief, with its sensitivity decreasing whe n response times in the fast condition get longer. This regularity was confirmed by a detailed analysis of the published evidence from Stern berg's task and was not attributable to speed-accuracy trade-off or to different methods of parametrization. The structures generating the s calp P3b are involved both in stimulus processing and in response sele ction. Response selection may exert its effect on P3 in one of two way s: either directly, fully delaying P3 latency, or affecting a second P 3 component (P-CR) only, thus having an attenuated effect on P3 latenc y.