Two distinct stimulus-locked EEG signatures reliably encode domain-general confidence during decision formation

Abstract

Decision confidence, an internal estimate of how accurate our choices are, is essential for metacognitive self-evaluation and guides behaviour. However, it can be suboptimal and hence understanding the underlying neurocomputational mechanisms is crucial. To do so, it is essential to establish the extent to which both behavioural and neurophysiological measures of metacognition are reliable over time and shared across cognitive domains. The evidence regarding domain-generality of metacognition has been mixed, while the test-retest reliability of the most widely used metacognitive measures has not been reported. Here, in human participants of both sexes, we examined behavioural and electroencephalographic (EEG) measures of metacognition across two tasks that engage distinct cognitive domains - visual perception and semantic memory. The test-retest reliability of all measures was additionally tested across two experimental sessions. The results revealed a dissociation between metacognitive bias and efficiency, whereby only metacognitive bias showed strong test-retest reliability and domain-generality whilst metacognitive efficiency (measured by M-ratio) was neither reliable nor domain-general. Hence, overall confidence calibration (i.e., metacognitive bias) is a stable trait-like characteristic underpinned by domain-general mechanisms whilst metacognitive efficiency may rely on more domain-specific computations. Additionally, we found two distinct stimulus-locked EEG signatures related to the trial-by-trial fluctuations in confidence ratings during decision formation. A late event-related potential was reliably linked to confidence across cognitive domains, while evoked spectral power predicted confidence most reliably in the semantic knowledge domain. Establishing the reliability and domain-generality of neural predictors of confidence represents an important step in advancing our understanding of the mechanisms underlying self-evaluation. Significance StatementUnderstanding the mechanisms underlying metacognition is essential for addressing deficits in self-evaluation. Open questions exist regarding the domain-generality and reliability of both behavioural and neural measures of metacognition. We show that metacognitive bias is reliable across cognitive domains and time, whereas the most adopted measure of metacognitive efficiency is domain-specific and shows poor test-retest reliability. Hence, more reliable measures of metacognition, tailored to specific domains, are needed. We further show that decision confidence is linked to two EEG signatures: late event-related potentials and evoked alpha/beta spectral power. While the former predicts confidence in both perception and semantic knowledge domains, the latter is only reliably linked to knowledge confidence. These findings provide crucial insights into the computations underlying metacognition across domains.