Do performance-monitoring related cortical potentials mediate fluency and difficulty effects on decision confidence?

It remains unclear to what extent the performance-monitoring (PM) processes involved in perceptual decisions are also involved in more complex reasoning decisions. To address this problem, we examined the role of PM-related cortical potentials in decision confidence. In simple perceptual decisions, the amplitude of these potentials has been shown to correlate with errors on the one hand and confidence ratings on the other. We therefore asked whether PM-related potentials mediate the effects of experimental manipulations of decision confidence on confidence ratings in an arithmetic reasoning task. In an EEG experiment, 49 participants had to quickly decide whether an equation (e.g. 9 * 7 = 65) was correct or incorrect and then report their confidence in that decision. Task difficulty and response fluency were varied to manipulate confidence. Pooling responses across correct as well as incorrect trials, we analyzed amplitudes of Error-Related Negativity (pooled ERN) and Error Positivity (pooled Pe). The results indicated that although pooled ERN and pooled Pe correlated with task difficulty, neither potential mediated the effect of task difficulty on confidence. Response fluency had an effect on confidence only for simple problems and this effect was partially mediated by pooled ERN but not by pooled Pe. These results suggest that pooled ERN and pooled Pe may reflect implicit performance monitoring, whereas pooled ERN may mediate the effect of the fluency heuristic on decision confidence. decision confidence, mental arithmetic, ERN, Pe, fluency, task difficulty, ACC, performance-monitoring