Alternative Non-drug Reinforcer Research Articles

Income alters choice between drug and an alternative nondrug reinforcer in monkeys.

Income alters choice between drug and an alternative nondrug reinforcer in monkeys.

Income alters choice between drug and an alternative nondrug reinforcer in monkeys.

Income alters choice between drug and an alternative nondrug reinforcer in monkeys.

Choice between cocaine and food by rhesus monkeys

The present experiment was designed to examine the effects of the conditions of food availability on choice between cocaine and food in rhesus monkeys. Monkeys (n = 3), maintained at approximately 90% of their free-feeding weights, were trained in a discrete-trials choice procedure and allowed to choose between intravenous injections of cocaine (0.03-1.0mg/kg/injection) and food delivery (4 pellets; 1g/pellet) during daily 7-h sessions. When food was available both within the session and by supplemental post-session feeding, the frequency of cocaine choice increased in a dose-related manner for all monkeys. When supplemental post-session feeding was eliminated (i.e. food was only available within the session) the cocaine dose-response function was shifted to the right and down relative to that found initially. However, changes in the frequency of cocaine choice did not vary consistently with changes in body weight. Thus, these results suggest that the reinforcing efficacy of cocaine can be modified by changing the conditions of availability of an alternative non-drug reinforcer.

Effects of increasing the magnitude of an alternative reinforcer on drug choice in a discrete-trials choice procedure

Rhesus monkeys were trained in a discrete-trials choice procedure and allowed to choose between food delivery (1-16 pellets; 1 g/pellet) and intravenous injections of cocaine (0.03-0.56 mg/kg/injection; N = 4) or procaine (1.0-10 mg/kg/injection; N = 4) during daily 3-h sessions. Injections were available as the alternative to food. When the amount of food available as the alternative to drug was held constant and dose of drug was varied, the frequency of drug choice and total drug intake increased in a dose-related fashion for both cocaine and procaine. For both drugs, when the amount of food available as the alternative to drug was increased and the dose of the drug was held constant, the frequency of drug choice and total drug intake decreased. Thus, increases in the magnitude of an alternative non-drug reinforcer decreased cocaine and procaine self-administration. Further, the results suggest that while increasing the magnitude of the alternative reinforcer decreased the potency of cocaine as a positive reinforcer, the reinforcing efficacy of procaine was decreased. Because drug use by humans typically occurs in a context in which other reinforcers are available, the present results are consistent with the hypothesis that drug self-administration by humans can be decreased by increasing the value of alternative positive reinforcers. In addition, these results suggest that the extent to which drug self-administration is sensitive to this manipulation varies across drugs.

MODIFYING DRUG‐REINFORCED BEHAVIOR BY ALTERING THE ECONOMIC CONDITIONS OF THE DRUG AND A NONDRUG REINFORCER

Six rhesus monkeys were trained to self-administer orally delivered phencyclidine (0.25 mg/mL) and saccharin (0.03% wt/vol) under concurrent fixed-ratio 16 schedules. In Condition 1 the fixed-ratio requirement for phencyclidine was changed from 16 to 4, 8, 16, 32, 64, 128 and 16 while the fixed-ratio requirement for saccharin deliveries remained constant at 16. In Condition 2 the fixed-ratio value for saccharin was systematically altered while the fixed-ratio requirement for phencyclidine remained at 16, and in Condition 3 the fixed-ratio requirements for both phencyclidine and saccharin were altered simultaneously. Water was then substituted for saccharin, and the series of fixed-ratio manipulations was replicated. The phencyclidine concentration was reduced to 0.125 mg/mL and Conditions 1 and 3 were repeated. When the fixed-ratio requirement for phencyclidine was increased and the fixed-ratio requirement for saccharin or water remained fixed at 16, phencyclidine deliveries decreased when saccharin (vs. water) was concurrently available. The magnitude of the decrease ranged from 20% to 90% (of the concurrent water condition) as the fixed-ratio requirement for phencyclidine increased from 4 to 128. When the fixed-ratio requirement for phencyclidine remained at 16 and the fixed-ratio requirements for concurrent saccharin or water varied between 4 and 128, phencyclidine deliveries decreased by 30% to 40% due to the concurrent availability of saccharin (vs. water). This decrease occurred only at the three lowest fixed-ratio values when saccharin intake was relatively high. When the fixed-ratio requirements for both phencyclidine and concurrent saccharin or water were varied simultaneously, phencyclidine deliveries were reduced from 20% to 45% when saccharin (vs. water) was concurrently present. There was little effect of reducing the phencyclidine concentration when the data were analyzed in terms of unit price (responses per milligram). Thus, changes in the fixed-ratio requirement or drug concentration were functionally similar, and unit price of phencyclidine was the variable that was influenced by the presence of concurrent saccharin. These data indicate that drug-reinforced behavior is substantially reduced when the environment is enriched with an alternative nondrug reinforcer. The economic context in which these substances are presented is an important determinant of drug-reinforced behavior.