Figure 1
Three trial types with stimulus–response–outcome associations (left panel) and their involved learning systems (right panel). The standard and congruent discriminations can be resolved with both the goal-directed and the habit system. In contrast, the incongruent discrimination can only be resolved using the habit system. During instrumental learning in the flexible goal-directed system, the outcome is represented in the associative structure, allowing incentive evaluation of the outcome to impact on action selection. In the habit system, behavior is directly triggered by environmental stimuli via S–R associations, rendering action selection relatively efficient but also inflexible.
