Confidence matching in group decision-making

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Abstract

Most important decisions in our society are made by groups, from cabinets and commissions to boards and juries. When disagreement arises, opinions expressed with higher confidence tend to carry more weight1,2. Although an individual’s degree of confidence often reflects the probability that their opinion is correct3,4, it can also vary with task-irrelevant psychological, social, cultural and demographic factors59. Therefore, to combine their opinions optimally, group members must adapt to each other’s individual biases and express their confidence according to a common metric1012. However, solving this communication problem is computationally difficult. Here we show that pairs of individuals making group decisions meet this challenge by using a heuristic strategy that we call ‘confidence matching’: they match their communicated confidence so that certainty and uncertainty is stated in approximately equal measure by each party. Combining the behavioural data with computational modelling, we show that this strategy is effective when group members have similar levels of expertise, and that it is robust when group members have no insight into their relative levels of expertise. Confidence matching is, however, sub-optimal and can cause miscommunication about who is more likely to be correct. This herding behaviour is one reason why groups can fail to make good decisions1012.

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Figure 1: Theoretical and experimental framework.
Figure 2: Behavioural evidence for confidence matching.
Figure 3: Confidence matching is sub-optimal.
Figure 4: Confidence matching at short time scales.

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Acknowledgements

This work was supported by the Calleva Research Centre for Evolution and Human Sciences at Magdalen College (D.B. and J.Y.F.L.), the Gatsby Charitable Foundation (L.A. and P.E.L.), the DAAD (A.M.), the Wellcome Trust (S.H.C.: 099741/Z/12/Z), and the European Research Council (B.B.: 309865-NeuroCoDec; C.S.: 281628-URGENCY). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

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D.B., J.Y.F.L., B.B. and C.S. conceived the study and designed the experiments. D.B., S.H.C., B.R. and A.M. performed the experiments. D.B., L.A., R.M., P.E.L. and C.S. developed the models and the simulations. D.B. analysed the data and performed the simulations. D.B., L.A., R.M., S.H.C., P.E.L., B.B. and C.S. interpreted the results. D.B. drafted the manuscript. D.B., L.A., R.M., P.E.L., B.B. and C.S. wrote the manuscript.

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Correspondence to Dan Bang.

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The authors declare no competing interests.

Supplementary information

Supplementary Information

Supplementary Methods, Supplementary Notes, Supplementary Figures 1–9, Supplementary Tables 1–2.

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Bang, D., Aitchison, L., Moran, R. et al. Confidence matching in group decision-making. Nat Hum Behav 1, 0117 (2017). https://doi.org/10.1038/s41562-017-0117

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