Domain generality is an emergent, not inherent, property of metacognition

We experience some level of confidence in all decisions we make, yet our understanding of how confidence is generated remains elusive. Here we examine three potential aspects of metacognitive confidence judgements that could be similar across the distinct domains of memory and perception in adults (n = 236) and children (aged four to seven years, n = 263; 122 girls and 141 boys) from Vancouver, Canada. Using episodic memory and perceptual tasks, we reveal that while confidence bias correlates across domains at all ages, confidence sensitivity and efficiency are both distinct. Crucially, children aged six and older can flexibly contrast confidence states across memory and perceptual decisions, indicating a shared internal metric of confidence. In contrast, four-to-five-year-old children struggle with cross-domain comparisons, highlighting a developmental transition in metacognitive processing. Overall, our findings highlight the distinct yet commensurable nature of memory and perceptual confidence, with domain-general processes emerging by age six.