Tolerance to the effects of cocaine on performance under behavior-correlated reinforcement magnitude.
Cocaine's power to speed or slow pigeons' timed pecking fades with repeated use even when food keeps coming.
01Research in Context
What this study did
Pigeons pecked a key for food on an 8-minute fixed-interval schedule. The birds earned bigger food portions when they timed their pecks well.
Each day the birds got a cocaine shot before the session. Doses ranged from 0.3 to 10 mg/kg. The team ran this for weeks to see what changed.
What they found
Low cocaine doses sped the birds up. High doses slowed them down. This upside-down U shape stayed true day after day.
Over weeks the same dose stopped working. Birds pecked faster again even on high doses. Their timing patterns also returned to normal even though cocaine kept coming.
How this fits with other research
Finney et al. (1995) saw the same U-shaped curve in single sessions. Gabriels et al. (2001) now shows that curve flattens out after many days. The two papers link like a before-and-after photo.
Burgess et al. (1986) found that past training with mixed punishment schedules decides how morphine will act later. Gabriels et al. (2001) shows a similar idea: long drug history, not just the dose, controls final performance.
Together the work says both past contingencies and past drug days write the script for what a drug does today.
Why it matters
If you run medication-plus-behavior plans, remember that early success can fade as the body adapts. Track response patterns across weeks, not just days. When rate or timing drifts back toward baseline, the drug may not be failing; tolerance could be growing. Plan dose reviews and schedule tweaks at steady calendar points so the program stays ahead of the curve.
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02At a glance
03Original abstract
Four pigeons responded under a fixed-interval 8-min schedule of food delivery in which the amount of food delivered at the end of each interval depended on performance during the interval (i.e., a correlated schedule). Specifically, duration of access to grain was contingent upon the number of responses made during the first 4 min of the interval. This differential outcome did not affect response rates or patterning relative to performance under a simple fixed-interval 8-min schedule. Behavior under the correlated schedule was then investigated under doses of cocaine ranging from 0.3 to 10.0 mg/kg. A bitonic dose-response function was obtained for response rates and the time with head in the food hopper, whereas dose-dependent decreases were observed in the mathematical index of curvature (Fry, Kelleher, & Cook, 1960). The dose that produced the greatest increase in the head-in-hopper time was then administered prior to each session. Following repeated administration of cocaine, disruptions in response patterning were attenuated for all 4 pigeons; tolerance was also observed to the rate-increasing effects and increased head-in-hopper time for 2 pigeons after chronic cocaine administration. Tolerance therefore developed despite the fact that the initial effect of cocaine was to increase the amount of food obtained.
Journal of the experimental analysis of behavior, 2001 · doi:10.1901/jeab.2001.76-217