Behavior controlled by scheduled injections of cocaine in squirrel and rhesus monkeys.
Cocaine can keep primates working on FI and FR schedules, but FI patterns resist dose changes better than FR.
01Research in Context
What this study did
Scientists gave squirrel and rhesus monkeys cocaine on fixed-ratio and fixed-interval schedules.
They watched if the drug could keep the animals pressing a lever in the same steady patterns that food produces.
What they found
Cocaine kept the monkeys working in the usual FR and FI patterns.
FI patterns stayed steady even when the cocaine dose changed; FR patterns wobbled more.
How this fits with other research
Dykens et al. (1991) later showed that small FR schedules make tolerance grow faster, while big FR schedules leave stronger after-effects.
Bromley et al. (1998) found the same FR cocaine effect in oral self-dosing and proved that monkeys "buy" cocaine like shoppers: higher unit price means less consumption.
Kanter et al. (2010) moved from monkeys to pigeons and showed that daily cocaine makes locomotion speed up for weeks, even after the drug stops.
Why it matters
The study tells you that schedule type, not just the drug, controls behavior. FI schedules buffer against dose changes, so if you ever model drug-maintained behavior, use FI when you need steady responding and FR when you want to see disruption.
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02At a glance
03Original abstract
Rates and patterns of key-press responding maintained under schedules in which responding resulted in intravenous injections of cocaine were studied in squirrel monkeys and rhesus monkeys. Each injection was followed by a 60- or 100-sec timeout period. Schedule-controlled behavior was obtained at appropriate cocaine doses in each species. Under FR 10 or FR 30 schedules, performance was characterized by high rates of responding (usually more than one response per second) in each ratio. Under FI 5-min schedules, performance was characterized by an initial pause, followed by acceleration of responding to a final rate that was maintained until the end of the interval. Under multiple fixed-ratio fixed-interval schedules, rates and patterns of responding appropriate to each schedule component were maintained. Responding seldom occurred during timeout periods under any schedule studied. At doses of cocaine above or below those that maintained characteristic schedule-controlled behavior, rates of responding were relatively low and patterns of responding were irregular. Characteristic fixed-interval responding was maintained over a wider range of cocaine doses than characteristic fixed-ratio responding. Complex patterns of responding controlled by discriminative stimuli under fixed-ratio or fixed-interval schedules can be maintained by cocaine injections in squirrel monkeys and rhesus monkeys.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-93