Priming effects with drugs and other reinforcers

Abstinent drug users often report that taking even a small amount of their previously abused drug increases their desire for the drug and can lead to a full relapse. This apparent ''priming'' effect of drugs has been studied in both laboratory animals and humans. In animals trained to self-administer drugs, small amounts of a previously self-administered drug readily reinstate responding. In humans, administration of a previously abused drug increases self-reported craving and desire for the drug. Priming effects also occur with other reinforcers (e.g., presentation of a food stimulus increases food-reinforced responding). This article examines the generality of priming phenomena, and it examines some of the learned or unlearned processes that underlie the effect.