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The idiosyncratic nature of confidence


Confidence is the ‘feeling of knowing’ that accompanies decision-making. Bayesian theory proposes that confidence is a function solely of the perceived probability of being correct. Empirical research has suggested, however, that different individuals may perform different computations to estimate confidence from uncertain evidence. To test this hypothesis, we collected confidence reports in a task in which subjects made categorical decisions about the mean of a sequence. We found that for most individuals, confidence did indeed reflect the perceived probability of being correct. However, in approximately half of them, confidence also reflected a different probabilistic quantity: the perceived uncertainty in the estimated variable. We found that the contribution of both quantities was stable over weeks. We also observed that the influence of the perceived probability of being correct was stable across two tasks, one perceptual and one cognitive. Overall, our findings provide a computational interpretation of individual differences in human confidence.

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Fig. 1: Tracking mean evidence in rapid serial visual presentations.
Fig. 2: Estimating confidence.
Fig. 3: Analysis of confidence across individuals.
Fig. 4: Stability across time.
Fig. 5: Decisions and confidence in experiment 3 (N = 20).
Fig. 6: Consistency across tasks involving uncertainty in the perceptual and cognitive domain. Twenty participants that were not tested in experiments 1 or 2 performed one visual and one numerical task (experiment 3). As in Fig. 3, we decomposed confidence in terms of the weight of \(\hat{p}\left({\rm{correct}}\right)\) (β p), the weight of information (β I), and the overall confidence (α 3).

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J.N. and B.B. were supported by the European Research Council StG (NEUROCODEC, no. 309865); C.H. was supported by a studentship from the Medical Research Council (UK); H.F. was supported by a Chevening scholarship; M.K. and P.E.L. were supported by the Gatsby Charitable Foundation. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

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Authors and Affiliations



J.N. and B.B. designed the experiments. J.N., C.H. and H.F. conducted the experiments. J.N., M.K., P.E.L. and B.B. developed the analysis approach and computational models. J.N. analysed the data. J.N., P.E.L. and B.B. wrote the paper.

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Correspondence to Joaquin Navajas.

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Navajas, J., Hindocha, C., Foda, H. et al. The idiosyncratic nature of confidence. Nat Hum Behav 1, 810–818 (2017).

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