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A rational model of the Dunning–Kruger effect supports insensitivity to evidence in low performers



Evaluating one’s own performance on a task, typically known as ‘self-assessment’, is perceived as a fundamental skill, but people appear poorly calibrated to their abilities. Studies seem to show poorer calibration for low performers than for high performers, which could indicate worse metacognitive ability among low performers relative to others (the Dunning–Kruger effect). By developing a rational model of self-assessment, we show that such an effect could be produced by two psychological mechanisms, in either isolation or conjunction: influence of prior beliefs about ability or a relation between performance and skill at determining correctness on each problem. To disentangle these explanations, we conducted a large-scale replication of a seminal paper with approximately 4,000 participants in each of two studies. Comparing the predictions of two variants of our rational model provides support for low performers being less able to estimate whether they are correct in the domains of grammar and logical reasoning.

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Fig. 1: Graphical representation of the model.
Fig. 2: Model predictions in a toy example where participants solve ten problems in the baseline model (μθ, μβ = 0, σθ, σβ = 1 and ϵ = 0).
Fig. 3: Model predictions in a toy example.
Fig. 4: Histograms of results in the two studies.
Fig. 5: Findings of the grammar study.
Fig. 6: Findings of the logical reasoning study.

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Data availability

The anonymized data that support the findings of this study are available on the Open Science Framework (

Code availability

The Qualtrics code that generates the surveys is available in the same repository ( on the Open Science Framework. All code used for analyses and the model are available on GitHub (


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The authors received no specific funding for this work.

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Authors and Affiliations



R.A.J. designed the studies, collected data, developed the model and performed the simulations. A.N.R. and T.L.G. supervised the study design and model development. All authors discussed the results and contributed to the final manuscript.

Corresponding author

Correspondence to Rachel A. Jansen.

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The authors declare no competing interests.

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Peer review informationNature Human Behaviour thanks Stephen Fleming, Sam Gilbert and Matthew Rhodes for their contribution to the peer review of this work. Primary Handling Editor: Marike Schiffer.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Interpreting σθ.

Model predictions in a toy example where participants solve 10 problems (a) when the standard deviation on ability (σθ) is adjusted (σθ = 1 or 2) and (b) when both this and the parameter ϵ are adjusted (σθ= 1, ϵ = 0.35 or ϵ = 0, σθ= 0.5) to reveal comparable results. In the main paper, we consider a single value for the standard deviation of the prior on ability (σθ). As shown in Fig. 1a, increasing the standard deviation of the prior implies more accurate estimation of scores, although some under and over estimation is still present. The pattern of Fig. 1a is similar to the pattern of predictions when changing ϵ. As shown in Fig. 1b, adjustments to either of these parameters can lead to very similar predictions for the relationship between true scores and estimated scores. This is not surprising given that both of these parameters represent uncertainty. Choosing to focus on fitting participants' values of ϵ allows us to capture variation in estimates of correctness on each question. On the other hand, if we were to focus on fitting participants' σθ values, we would be assuming variation in prior beliefs about ability. Given the framing of the Dunning–Kruger effect in terms of sensitivity to errors, we fixed σθ and focused on ϵ in our modeling approach. We have expressed our conclusions in terms consistent with variation in either ϵ or σθ, which affect the degree of updating of prior beliefs in light of evidence.

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Jansen, R.A., Rafferty, A.N. & Griffiths, T.L. A rational model of the Dunning–Kruger effect supports insensitivity to evidence in low performers. Nat Hum Behav 5, 756–763 (2021).

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