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Confirmation bias in human reinforcement learning: Evidence from counterfactual feedback processing

Fig 2

Factual and counterfactual learning biases.

(A) Predicted results. Based on previous studies we expected that in Experiment 1 factual learning would display a “positivity” bias (i.e. the learning rate for the chosen positive outcomes would be relatively higher than that of the chosen negative outcomes (; note that in Experiment 1 the “positivity” and the “confirmation” bias are not discernible). In Experiment 2, one possibility was that this “positivity” bias would extend to counterfactual learning, whereby positive outcomes would be over-weighted regardless of whether the outcome was chosen or unchosen (“valence” bias) (). Another possibility was that counterfactual learning would present an opposite bias, whereby the learning rate for unchosen negative outcomes was higher than the learning rate of unchosen positive outcomes () (“confirmation” bias). (B) Actual results. Learning rate analysis of Experiment 1 data replicated previous findings, demonstrating that factual learning presents a “positivity” bias. Learning rate analysis of Experiment 2 indicated that counterfactual learning was also biased, in a direction that was consistent with a “confirmation” bias. ***P<0.001 and *P<0.05, two-tailed paired t-test.

doi: https://doi.org/10.1371/journal.pcbi.1005684.g002