[Event related brain potentials and signal detection: decision confidence and signal probability]

This paper is concerned with the relation of two components of the late positive complex, P300 and slow wave, to parameters of signal detection theory. In the first experiment, basically a replication of Squires et al., signal probability was 50% and a six point rating scale was used for subjects' answers. Whereas for the P300 the well known relation to subjective confidence (and thus to response criteria) was confirmed, a similar relation could not be found for the slow wave. In the second experiment the local signal probability was varied from 25% to 75% on a trial to trial basis. Under these conditions neither the P300 nor the slow wave exhibited a relation to signal-probability, whilst the relation to decision-confidence was preserved.