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Confidence and certainty: distinct probabilistic quantities for different goals

Abstract

When facing uncertainty, adaptive behavioral strategies demand that the brain performs probabilistic computations. In this probabilistic framework, the notion of certainty and confidence would appear to be closely related, so much so that it is tempting to conclude that these two concepts are one and the same. We argue that there are computational reasons to distinguish between these two concepts. Specifically, we propose that confidence should be defined as the probability that a decision or a proposition, overt or covert, is correct given the evidence, a critical quantity in complex sequential decisions. We suggest that the term certainty should be reserved to refer to the encoding of all other probability distributions over sensory and cognitive variables. We also discuss strategies for studying the neural codes for confidence and certainty and argue that clear definitions of neural codes are essential to understanding the relative contributions of various cortical areas to decision making.

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Figure 1: Confidence and certainty in a visuo-vestibular task.
Figure 2: Two distinct codes for certainty.
Figure 3: Nonlinear neural computations by neural populations that linearly represent variables.
Figure 4: A Bayesian decoder provides a normative way to relate population activity (left) to the certainty (right).

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Acknowledgements

The authors would like to thank Z. Mainen, R. Kiani, P. Latham, P. Dayan, J. Sanders and B. Hangya for stimulating discussions about the definition and utility of the concept of confidence and A. Urai and P. Masset for comments on the manuscript. This work was supported by grants from the Simons Global Brain Initiative (A.P.) and the US National Institutes of Health (R01MH097061) to A.K.

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Correspondence to Alexandre Pouget.

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Pouget, A., Drugowitsch, J. & Kepecs, A. Confidence and certainty: distinct probabilistic quantities for different goals. Nat Neurosci 19, 366–374 (2016). https://doi.org/10.1038/nn.4240

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