Serial dependence of confidence judgments reveals metacognitive adaptation

In three experiments (n = 20 each), we investigated the mechanisms by which the metacognitive system produces the confidence serial dependence (CSD) effect in a series of perceptual decisions. We found that confidence ratings were systematically attracted to those in preceding trials (similar to “confidence leak”), even with matched performance. We further found that CSD required explicit confidence judgments in preceding decisions and was largely independent of preceding motor response patterns. By comparing a factorial combination of computational models, we found that CSD arises from the jittering of a fixed decision criterion template based on past information instead of from dynamically updating criteria across trials. As our study focuses on decisions on a lab-based visual motion task, our model needs to be tested against data from other tasks and scenarios. Our results suggest that our metacognition adapts in response to recent perceptual decisions.