Confidence tracks sensory- and decision-related ERP dynamics during auditory detection

Recent research has focused on measuring neural correlates of metacognitive judgments in decision and post-decision processes during memory retrieval and categorization. However, many tasks (e.g., stimulus detection) may require monitoring of earlier sensory processing. Here, participants indicated which of two intervals contained an 80-ms pure tone embedded in white noise. One frequency (e.g., 1000 Hz) was presented on ∼80% of all trials (i.e., 'primary' trials). Another frequency (e.g., 2500 Hz) was presented on ∼20% of trials (i.e., 'probe' trials). The event-related potential (ERP) was used to investigate the processing stages related to confidence. Tone-locked N1, P2, and P3 amplitudes were larger for trials rated with high than low confidence. Interestingly, a P3-like late positivity for the tone-absent interval showed high amplitude for low confidence. No 'primary' vs. 'probe' differences were found. However, confidence rating differences between primary and probe trials were correlated with N1 and tone-present P3 amplitude differences. We suggest that metacognitive judgments can track both sensory- and decision-related processes (indexed by the N1 and P3, respectively). The particular processes on which confidence judgments are based likely depend upon the task an individual is faced with and the information at hand (e.g., presence or absence of a signal).