Figure 1.

Experiment 1, experimental design. Each trial started with a central fixation point (presented for 0.5–0.7 s), followed by a face that subjects had to categorize as flexible or determined as quickly as possible and before the face disappearance. The face remained on-screen until subjects’ response or for up to 1.5 s. In both the pre- and post-association phases, a confidence rating screen was then presented. Subjects had to rate the confidence they had in their personality judgment between one (random guess) to six (absolutely sure). Inter-trial interval was initiated by subjects’ response or after up to 4 s. In the association phase, there was no confidence rating after the categorization response but subjects were given a 1 s feedback on the accuracy of this response. Unknown to the subject, the feedback was based on the inter-eye distance of the face presented. There was no stimulus repetition across the successive phases of the study; every face and every face feature (including the eyes) were new for each phase.