Figure 1.

Paradigm. In each trial, two faces and a monetary amount were displayed. One of the two faces was associated with 75% probability of receiving an outcome (and 25% probability of receiving nothing, DS₊) and the other with 25% probability of receiving an outcome (and 75% of receiving nothing, DS₋). Outcomes always included both the displayed monetary amount and a skin stimulation (touch or pain). Participants were free to choose either of the two faces. To maximize gain and minimize pain, participants should choose the DS₋ when the monetary amount was zero or negative. Critically, a positive monetary amount introduced a conflict between the goals of gain maximization and pain minimization. Choice consequences were revealed at the offset of the decision screen with outcome delivery determined according to the probability associated with the chosen face.