Date Added: May 2010
Decisions can arise in different ways, such as from a gut feeling, doing what worked last time, or planful deliberation. Different decision-making systems are dissociable behaviorally, map onto distinct brain systems, and have different computational demands. For instance, "Model-free" decision strategies use prediction errors to estimate scalar action values from previous experience, while "model-based" strategies leverage internal forward models to generate and evaluate potentially rich outcome expectancies. Animal learning studies indicate that expectancies may arise from different sources, including not only forward models but also Pavlovian associations, and the flexibility with which such representations impact behavior may depend on how they are generated.