Global visual confidence

Abstract

Visual confidence is the observers' estimate of their precision in one single perceptual decision. Ultimately, however, observers often need to judge their confidence over a task in general rather than merely on one single decision. Here, we measured the global confidence acquired across multiple perceptual decisions. Participants performed a dual task on two series of oriented stimuli. The perceptual task was an orientation-discrimination judgment. The metacognitive task was a global confidence judgment: observers chose the series for which they felt they had performed better in the perceptual task. We found that choice accuracy in global confidence judgments improved as the number of items in the series increased, regardless of whether the global confidence judgment was made before (prospective) or after (retrospective) the perceptual decisions. This result is evidence that global confidence judgment was based on an integration of confidence information across multiple perceptual decisions rather than on a single one. Furthermore, we found a tendency for global confidence choices to be influenced by response times, and more so for recent perceptual decisions than earlier ones in the series of stimuli. Using model comparison, we found that global confidence is well described as a combination of noisy estimates of sensory evidence and position-weighted response-time evidence. In summary, humans can integrate information across multiple decisions to estimate global confidence, but this integration is not optimal, in particular because of biases in the use of response-time information.

Keywords: Confidence; Integration; Metacognition; Perception; Vision.

Fig. 1

Illustration of the trial procedures for (A) Experiment 1 and (B) Experiment 2. (A) In Experiment 1, in each confidence-comparison trial, two sets of one, two, four, or eight oriented Gabor stimuli were presented in succession (a set size of four is shown above as an example). During the presentation of stimuli in each set, observers viewed the stimuli without giving any perceptual responses. Based on the confidence-choice response, one stimulus randomly sampled from the chosen set would be presented afterwards. Observers then performed the perceptual task on this stimulus. (B) In Experiment 2, procedure was identical to that in Experiment 1, except that observers performed the orientation-discrimination task on every stimulus within a set immediately after it had been presented. After the presentation of all stimuli for both sets, participants completed the global confidence-comparison task by indicating the set in which they had greater confidence overall in performing the perceptual task

Fig. 2

Results of Experiment 1. (A) Histogram of overall confidence-choice d’ across observers. Solid horizontal line with notches shows the 95% confidence interval for the mean. (B) Change in confidence-choice d’ as a function of set size across Experiments 1A, 1B, and 1C. Error bars represent ± 1 standard error of the mean. (C) Histogram of set-size effects across observers. Solid horizontal line with notches shows the 95% confidence interval for the mean

Fig. 3

Results of Experiment 2. (A) Changes in metacognitive sensitivities with set size. Global metacognitive sensitivity as a function of set size for participants. Open circles (light lines) represent results of individual participants, filled circles (dark line) represent the means. The set-size effect is the slope of the regression of metacognitive sensitivity against set size (in log-units). (B) Weights for each position within a set to favor the first set. Weights were extracted from logistic regression analyses predicting the probability of confidence choice based on perceptual accuracy (in orange) and the reciprocal of response time (in blue) for each set size (1, 2, 4, and 8). Weights for the overall bias to choose systematically the first set are small and are shown in darker colors to the right of each panel. Error bars represent 1 SEM