Second‐order schedules and the analysis of human drug‐seeking behavior

Behavior maintained by drug injections can be enhanced by using simple schedules as components of more complex second‐order schedules. Under second‐order schedules, completion of the component schedule, rather than an individual response, produces the drug injection according to another schedule. Each component schedule terminates with the brief presentation of a stimulus that has been associated with drug injection. Research over the past 30 years using these procedures with monkeys and human subjects has allowed an evaluation of the role of conditioned environmental stimuli in the acquisition, maintenance, extinction, and reinstatement of drug‐‐seeking behavior. These results have provided a cross‐validation of human and animal models of drug abuse which would not have been possible using simple schedules of reinforcement.