Cognitive modelling reveals distinct electrophysiological markers of decision confidence and error monitoring

Is confidence in perceptual decisions generated by the same brain processes as decision itself, or does confidence require metacognitive processes following up on the decision? In a masked orientation task with varying stimulus-onset-asynchrony, we used EEG and cognitive modelling to trace the timing of the neural correlates of confidence. Confidence as reported by observers increased with stimulus-onset-asynchrony in correct and to a lesser degree in incorrect trials, a pattern incompatible with established models of confidence. Electrophysiological activity in two different time periods was associated with confidence, namely, 350 - 500 ms after stimulus onset and 250 - 350 ms after the response. Cognitive modelling revealed that only the activity following on the stimulus exhibited the same statistical regularities as confidence, while the statistical pattern of the activity following the response was not compatible with confidence. It is argued that electrophysiological markers of decision confidence and error awareness are at least in parts distinct.