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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.
Bibliographical noteThis work was supported by Lingnan University to AL [DR18A7 (101097) and SSFRG/18/3/1 (102171)] and the French Agence Nationale de la Recherche [ANR-10-BLAN-1910 to PM; ANR-16-CE28-0002 to VdG; ANR-17-EURE-0017 to PM; ANR-18-CE28-0015 to PM & VdG]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The authors acknowledge constructive feedback from Tarryn Balsdon on earlier versions of the manuscript. A preliminary version of this work was presented at the annual meeting of the Vision Sciences Society in May 2014 in St. Pete Beach, Florida.