Concurrent nonindependent fixed-ratio schedules of alcohol self-administration: Effects of schedule size on choice

Choice dynamics in concurrent ratio schedules of reinforcement

The generalized matching law predicts performance on concurrent schedules when variable-interval schedules are programmed but is trivially applicable when independent ratio schedules are used. Responding usually is exclusive to the schedule with the lowest response requirement. Determining a method to program concurrent ratio schedules such that matching analyses can be usefully employed would extend the generality of matching research and lead to new avenues of research. In the present experiments, ratio schedules were programmed dependently such that responses to either of the two options progressed the requirement on both schedules. Responding is not exclusive because the probability of reinforcement increases on both schedules as responses are allocated to either schedule. In Experiment 1, performance on concurrent variable-ratio schedules was assessed, and reinforcer ratios were varied across conditions to investigate changes in sensitivity. Additionally, the length of a changeover delay was manipulated. In Experiment 2, performance was compared under concurrently available, dependently programmed variable-ratio and fixed-ratio schedules. Performance was well described by the generalized matching law. Increases in the changeover delay decreased sensitivity, whereas sensitivity was higher when variable-ratio schedules were employed, compared with fixed-ratio schedules. Concurrent ratio schedules can be a viable approach to studying functional differences between ratio and interval schedules.

Equal response rates maintained by concurrent drug and nondrug reinforcers: a design for treatment evaluation

During daily 3-h sessions, four rhesus monkeys had concurrent access to 16% alcohol (w/v) and saccharin. A response occurred when a monkey made mouth contact with the metal spout and thereby completed a drinkometer circuit. The liquids were available under concurrent nonindependent fixed-ratio 32 schedules. With these schedules, responses on the right spout decremented both the right and left fixed-ratio counters and vice versa. Responding was well maintained by both alcohol and saccharin. Increases in saccharin concentration produced increases in saccharin responding to the point that saccharin responding exceeded alcohol responding. Responses per saccharin delivery were also a direct function of the saccharin concentration. In contrast, responses per alcohol delivery generally decreased as the saccharin concentration became greater. Changeover or switching responses were also a direct function of the saccharin concentration. Relative reinforcing effects of each combination of liquid pairs were measured for each monkey. For all monkeys, it was possible to establish equal rates of responding for both reinforcers and frequent switching between reinforcers. The balanced responding can serve as a baseline for the evaluation of potential treatments that may alter relative reinforcing effects.

Addiction as a BAD, a Behavioral Allocation Disorder

Addiction is continued drug use despite its harm. As one always has alternatives, addiction can be construed as a decision to allocate behavior to drug use. While decision making is commonly discussed and studied as if it resulted from deliberative, evaluative processes, such processes are actually only rarely involved in behavior allocation. These deliberative processes are too slow, effortful and inefficient to guide behavior other than when necessary. Rather, most actions are guided by faster, more automatic processes, often labeled habits. Habits are mostly adaptive, and result from repeated reinforcement leading to over-learned behavior. Habitual behavior occurs rapidly in response to particular contexts, and the behavior occurring first is that which occurs, i.e., the behavior that is decided upon. Thus, as drug use becomes habitual, drug use is likely to be chosen over other available activities in that particular context. However, while drug use becoming habitual is necessary for addiction to develop, it is not sufficient. Typically, constraints limit even habitual drug use to safer levels. These constraints might include limiting occasions for use; and, almost always, constraints on amount consumed. However, in a minority of individuals, drug use is not sufficiently constrained and addiction develops. This review discusses the nature of these constraints, and how they might fail. These failures do not result from abnormal learning processes, but rather unfortunate interactions between a person and their environment over time. These accumulate in the maladaptive allocation of behavior to drug use. This Behavior Allocation Disorder (BAD) can be reversed; occasionally easily when the environment significantly changes, but more often by the arduous application of deliberative processes generally absent from decision making. These deliberative processes must continue until new more adaptive habits become the most probable behavior in the contexts encountered. As alternatives to drug use become the most probable behavior, relapse risk diminishes.