Testing architectures of the decision–confidence relation.

Two experiments examined the effect of rendering confidence judgments on the properties of the comparative decision process. In Experiment 1, participants worked for 12 sessions that required two-alternative perceptual, line-length comparisons. For sessions 1-4 and sessions 9-12, confidence judgments were not required. For sessions 5-8, participants provided confidence reports following each comparative judgment. The requirement of confidence judgments significantly increased decisional response time, suggesting that some confidence processing occurs in parallel with the primary decision process. Concomitantly, an examination of the properties of the time to determine confidence during sessions 5-8 revealed clear evidence of postdecisional confidence processing. These results were replicated in a second experiment requiring two-alternative comparative judgments of Canadian city populations. We conclude that confidence processing occurs both during the decision process and postdecisionally, and we discuss the implications of the present findings for current theories of confidence in human judgment.