Goal-Directed and Habitual Control in Human Drug Addiction

Abstract:

Learning theory has proposed that everyday actions are controlled by at least two dissociable systems: one that governs deliberate goal-directed actions and another that regulates automatic habits; these two systems are thought to have inherently different functions. The goal-directed system guides actions toward achieving specific outcomes; this system can flexibly adapt to changing situations, but it is more effortful. By contrast, the habit system automates repeated actions by linking them to environmental cues; this system enhances one’s efficiency by making actions more automatic, but at the cost of reduced sensitivity to the consequences. A large body of neuroscientific evidence suggests that an optimal balance between these two systems is critical to support adaptive behavior, and a breakdown of this balance may induce maladaptive behaviors. An example of this breakdown can be seen in the context of drug addiction, a psychiatric disorder characterized by maladaptive drug use that spirals out of control. Patients with drug addiction not only prioritize drug use over other key aspects of their lives (e.g., work, school, interpersonal relationships), they also struggle to reduce their drug use; in severe cases, their drug use may even persist despite recurrent physical and psychological harm. Even if patients manage to abstain from drugs for prolonged periods, exposure to environments that have previously been associated with drugs often triggers relapse. These clinical symptoms of drug addiction have been hypothesized to reflect an imbalance between goal-directed and habitual control over behavior, with a bias toward the latter. In this chapter, we review recent experimental work in humans in support of this hypothesis.