Habit Formation and Compulsion

Our increasing understanding of the psychological mechanisms involved in the transition from controlled to habitual compulsive drug use, the hallmark of drug addiction, relies on animal models in which the underlying behavioral construct reflects some of the main features of drug addiction in humans, such as foraging for the drug during extended periods of time, habitual drug seeking behavior and drug seeking or drug taking behaviors that are maintained despite adverse consequences. We have placed great emphasis on the development of behavioral procedures whereby animals not only self-administer drugs, but pathologically seek and take drugs in a way that resembles the clinical condition in human drug addicts. Thus, over the last 10 years we have developed models in rats that specifically address the development of habitual drug seeking behavior, compulsive cocaine seeking and taking behavior, and even addiction-like behavior. In this chapter, we review the behavioral procedures, namely second-order schedules of reinforcement, two-link heterogeneous chained schedules of reinforcement and the “three addiction-like behavioral criteria selection procedure” that we have used in rats to model habitual drug seeking behavior, compulsive drug seeking and taking behavior and addiction-like behavior. Although not yet widely adopted, these models have already contributed to the identification of some neurobiological and psychological mechanisms involved in the vulnerability to drug addiction and the transition from controlled to compulsive drug use, thereby emphasizing their great heuristic value in attempts to understand drug addiction.