Abstract
Perceptual decisions are accompanied by feelings of confidence that reflect decision validity. Though these feelings of confidence rely on perceptual evidence, dissociations between confidence and perceptual sensitivity are common. One explanation for these dissociations is that confidence utilises ongoing processing after the completion of perceptual decision processes (Pleskac and Busemeyer, 2010, Psych Rev). Here we demonstrate causal evidence for this claim by showing robust differences in confidence efficiency depending on the duration of post-decision time windows. We measured confidence efficiency using a forced-choice design: human observers chose which of two consecutive perceptual decisions was more likely to be correct. Post-decision time pressure was manipulated (whilst leaving stimulus presentation duration constant) by forcing observers to wait to enter their response, or cueing them to respond almost immediately (leaving limited time for ongoing processing before the next trial). This manipulation had limited effects on perceptual sensitivity, but large effects on confidence efficiency. The effect on confidence efficiency depended on the level of processing of the perceptual decision. For high-level perceptual decisions (discriminating the direction of gaze of an avatar face), confidence efficiency benefitted from additional time. But for low-level perceptual decisions about the same stimuli (discriminating the relative contrast of the eyes’ irises), confidence efficiency diminished with time. Over five experiments, we demonstrate the effect of perceptual decision-level within-subjects (Exp. 1 and 2) and the effect of time pressure within-subjects (Exp. 3 and 4). In Experiment 5, we generalise these findings to biological motion stimuli. Robust differences in confidence efficiency can be generated within-subjects, independently of perceptual sensitivity, by manipulating post-decision time windows. These results suggest that confidence strongly relies on the post-decisional processing of ongoing internal representations, that quickly degrade for low-level perception.