Behavioural task variants and computational model.

(A) Behavioural task variants. In Experiment 1 (leftmost panel) participants were shown only the outcome of the chosen option. In Experiment 2 (rightmost panel) participants were shown the outcome of both the chosen and the unchosen options. (B) Computational models. The schematic summarises the value update stage of our computational model. The model contains two computational modules, a factual learning module (in red) to learn from chosen outcomes (R_C) and a counterfactual learning module (in blue) to learn from unchosen outcomes (R_U) (note that the counterfactual learning module does not apply to Experiment 1). Chosen (Q_C) and unchosen (Q_U) option values are updated with delta rules that use different learning rates for positive and negative factual (PE_C) and counterfactual prediction errors (PE_U).