and Negus, in press). Animal models of self-administration (versus human models) have several advantages for medications development. For example, drugs that are not approved for use in humans can be evaluated; the effects of new treatment medications on patterns of drug self-administration can be evaluated quantitatively under controlled experimental conditions; social factors such as peer pressure or expectancy do not complicate interpretation of data; and accurate baseline measures of the daily dose and patterns of drug self-administration can be determined before, during, and after administration of the treatment medication. Additionally, the safety of the medication can be evaluated continually. Thus, the use of animal models for those aspects of medications development is parallel in importance to the earlier reliance on animal models of drug self-administration for evaluation of the abuse liability of new drugs. To the extent possible, however, these laboratory models should be employed across species to include humans.

A major contribution of behavioral research has been an understanding of the ways in which basic principles of learning and conditioning can be used to modify drug-taking behavior. These principles have been precisely defined so that they can be studied and replicated across conditions and species.

For example, research on drug effect expectancies suggests that learned beliefs and attitudes may serve as risk factors for the initiation and use of drugs (Brown, 1993). Further, epidemiological research has pointed to the importance of social modeling and attitudes as having strong impacts on drug use and abuse. Research on learning and conditioning has led to successful treatment models for drug abusers, including relapse prevention, community reinforcement, and focused techniques such as extinction training, relaxation training, contingency management, and job skills training. Two well-studied behavioral interventions are discussed below: contingency management and relapse prevention.

Contingency management research is based on the fact that, although drugs are potent reinforcers, there are non-drug reinforcers that can compete with drug use (see discussion of behavioral economics, below). Manipulation of the environment can shift the focus toward or away from drug reinforcers (e.g., Azrin et al., 1966; Barrett and Witkin, 1986). In the laboratory, monkeys will choose saccharine over phencyclidine if they are required to work substantially harder for the drug (Carroll and Rodefer, 1993). Research with humans has shown that experienced cocaine users will choose money or tokens over cocaine when the appropriate quantity and quality of alternative reinforcers are available (Foltin and Fischman,