Effects of cocaine on performance under fixed-interval schedules with a small tandem ratio requirement.
Cocaine tolerance spreads evenly across fixed-interval and fixed-ratio parts, so schedule structure—not response style—sets the fade speed.
01Research in Context
What this study did
Scientists gave rats repeated cocaine shots while they worked under a two-part schedule.
The schedule was a fixed-interval with a tiny fixed-ratio tag: wait 5 min, then emit 2 responses to cash in food.
They tracked how fast tolerance grew in each part to see if response pattern shaped the drug fade.
What they found
Tolerance showed up the same in both the wait part and the ratio part.
Because the response patterns differ—slow pausing vs quick bursts—the fade can’t be pinned on pattern alone.
Instead, the schedule parameter itself drives how fast cocaine loses its punch.
How this fits with other research
Locurto et al. (1980) already showed that ratio size flips cocaine from helpful to harmful.
Harris et al. (1978) proved an animal’s past schedule sets its baseline rate, which then decides if amphetamine speeds or slows responding.
McIntyre et al. (2002) later argued stimulants tweak rate, not the inner clock.
Together these papers build one line: schedule history sets the baseline, and the baseline governs how any stimulant—cocaine or amphetamine—will act.
Why it matters
If you run a tandem schedule with clients, know that drug or medication tolerance will grow evenly across parts.
You can’t count on different response styles to protect one component.
Watch the overall schedule parameter, not the pausing or bursting shape, when you judge how fast effects will fade.
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02At a glance
03Original abstract
Daily administration of cocaine often results in the development of tolerance to its effects on responding maintained by fixed-ratio schedules. Such effects have been observed to be greater when the ratio value is small, whereas less or no tolerance has been observed at large ratio values. Similar schedule-parameter-dependent tolerance, however, has not been observed with fixed-interval schedules arranging comparable interreinforcement intervals. This experiment examined the possibility that differences in rate and temporal patterning between the two types of schedule are responsible for the differences in observed patterns of tolerance. Five pigeons were trained to key peck on a three-component multiple (tandem fixed-interval fixed-ratio) schedule. The interval values were 10, 30, and 120 s; the tandem ratio was held constant at five responses. Performance appeared more like that observed under fixed-ratio schedules than fixed-interval schedules. Effects of various doses of cocaine given weekly were then determined for each pigeon. A dose that reduced responding was administered prior to each session for 50 days. A reassessment of effects of the range of doses revealed tolerance. The degree of tolerance was similar across components of the multiple schedule. Next, the saline vehicle was administered prior to each session for 50 days to assess the persistence of tolerance. Tolerance diminished in all subjects. Overall, the results suggested that schedule-parameter-dependent tolerance does not depend on the temporal pattern of responding engendered by fixed-ratio schedules.
Journal of the experimental analysis of behavior, 2004 · doi:10.1901/jeab.2004.82-293