Human confidence judgments are thought to originate from metacognitive processes that
provide a subjective assessment about one's beliefs. Alternatively, confidence is
framed in mathematics as an objective statistical quantity: the probability that a
chosen hypothesis is correct. Despite similar terminology, it remains unclear whether
the subjective feeling of confidence is related to the objective, statistical computation
of confidence. To address this, we collected confidence reports from humans performing
perceptual and knowledge-based psychometric decision tasks. We observed two counterintuitive
patterns relating confidence to choice and evidence: apparent overconfidence in choices
based on uninformative evidence, and decreasing confidence with increasing evidence
strength for erroneous choices. We show that these patterns lawfully arise from statistical
confidence, and therefore occur even for perfectly calibrated confidence measures.
Furthermore, statistical confidence quantitatively accounted for human confidence
in our tasks without necessitating heuristic operations. Accordingly, we suggest that
the human feeling of confidence originates from a mental computation of statistical
confidence.
