Figure 1.

The instrumental learning task (modified from Valentin et al., 2007). Participants completed three trial types (chocolate, orange, and neutral). On each trial, they were asked to choose between two actions represented by unique symbols. In each trial type, there was one action that led with a high probability to a food outcome and one action that led with a low probability to a food outcome. Depending on the trial type, the high probability action delivered chocolate milk and orange juice, respectively, with a probability of p = 0.50, a common liquid (peppermint tea) with a probability of p = 0.20, or nothing. The low probability action yielded the common outcome with a probability of p = 0.20. When an action was chosen, the related symbol was highlighted for 3 s before the outcome was delivered.