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 effect of drugs has been studied in both laboratory animals and humans. In animals trained to selfadminister 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. Abstinent drug users who consume even a small quantity of their previously preferred drug often report that the drug increases both the subjective desire for more of the drug and the likelihood of resuming regular use of the drug. One of the basic tenets of Alcoholics Anonymous is that a single alcoholic drink greatly increases the risk that an abstinent individual will relapse, or return to regular, excessive alcohol use (Alcoholics Anonymous, 1955). This effect is thought to occur even after long periods of abstinence and is even believed to extend to the alcoholic individual's responses to other classes of psychoactive drugs, such as tranquilizers and sedatives. Similarly, many cigarette smokers report that they failed in previous attempts to quit when they tested themselves, or sampled, even one or two puffs from a cigarette. Even ex-smokers who successfully abstain from smoking for lengthy periods of time report that having a single cigarette markedly increases their desire to smoke and their likelihood of relapsing. This apparent increase in the motivation to consume a drug after a single dose of the drug is referred to as the priming effect. Priming is likely to be an important factor in relapse to drug abuse. Whereas many drug users succeed in achieving an initial period of abstinence, most of these users relapse within a relatively short period of time. The relapse process is likely to consist of several phases, including, for example, an initial phase that results in the first re-use of the drug, and a secondary phase that begins' as soon as the drug is ingested. Shiffman (1986) has studied the factors involved in the initial phase using retrospective reports from relapsed drug users. Drug users reported that relapse episodes may be precipitated by a wide range of situations and stimuli, including positive and negative emotional states and intra- and interpersonal factors. During the second phase (i.e., after the drug is ingested), other factors may prevail. For example, the direct pharmacological effects of the drug or learned associations resulting from previous administrations of the drug may influence behavior.