Sequential effects on P3 in a counting task: A partial replication

High and low tones were presented in random order, and the high tones had to be counted. It was intended to replicate the sequential effects on P3 reported by Squires et al. (1976, 1977) and to test by means of an ANOVA approach how each one of the preceding four tones contributes to these sequential effects. However, results deviated from those studies: (1) P3s were generally somewhat larger with target tones than with nontargets; (2) Squires et al.'s (1976, 1977) sequential effects were replicated for nontargets, but were more or less reversed for targets. The preceding sequence was found also to exert influence on prestimulus baselines, N1, and EOG. It is suggested that target effects constitute the rule rather than the exception and that sequential effects on P3 may be altered by subtle differences of subjects' sets, similarly to sequential effects on choice reaction times.