Stoianov et al show how two mechanisms interact in the prefrontal cortex to support goal-directed behavior.  Categorization extracts behavioral abstractions (states) and reward-driven processes assign value to these categories

Stoianov, Ivilin, Aldo Genovesio, and Giovanni Pezzulo. “Prefrontal goal-codes emerge as latent states in probabilistic value learning.” Journal of Cognitive Neuroscience, in press.