Tolerance to and residual effects of cocaine in squirrel monkeys depend on reinforcement-schedule parameter.
Reinforcement-schedule parameters directly control both the development of drug tolerance and the persistence of residual behavioral effects.
01Research in Context
What this study did
Scientists gave squirrel monkeys cocaine before food sessions. The monkeys worked on fixed-ratio schedules that required 10, 30, or 100 lever presses for each food pellet.
The team watched how fast tolerance appeared and how long behavior stayed suppressed after each dose. They wanted to see if the work requirement changed the drug’s impact.
What they found
Small ratios led to quick tolerance. Monkeys on FR 10 kept pressing even after many cocaine shots.
Large ratios showed the opposite. Responding stayed low for days after the same dose. The schedule size controlled both tolerance speed and lingering suppression.
How this fits with other research
Gardner et al. (1976) first showed that cocaine can reinforce monkey behavior on fixed-ratio and fixed-interval schedules. Dykens et al. (1991) build on that by proving the ratio number itself shapes how fast tolerance grows.
Bromley et al. (1998) later extended the idea to oral cocaine in rhesus monkeys. They found that consumption follows unit price: higher lever costs reduce intake just like higher prices reduce shopping. The two studies align—schedule parameters set the value of the drug reinforcer.
Kanter et al. (2010) looked at pigeons, not monkeys, and measured locomotion instead of lever pressing. Still, both papers show residual effects: sensitization lingered weeks after cocaine ended, matching the long suppression seen under large fixed ratios.
Why it matters
Your client’s work requirement is a hidden variable. A child on FR 5 may adapt quickly to a new med, while a child on FR 50 may show lingering side effects. Start new drugs under lean schedules, then thin gradually. Watch responding the next day—if it stays low, the ratio may be too steep for the current dose.
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Join Free →Track post-dose responding across two ratio sizes; keep the leaner schedule if behavior stays suppressed under the denser one.
02At a glance
03Original abstract
Lever pressing by 4 squirrel monkeys was maintained under a three-component multiple fixed-ratio schedule of food presentation; components differed with respect to ratio size. For each monkey, acute administration of cocaine (0.03 to 1.3 mg/kg, i.m.) produced dose-dependent decreases in overall response rate in each component. During repeated daily administration of 1.0 mg/kg of cocaine, tolerance developed to the rate-decreasing effects under each of the ratio contingencies, but developed to a greater extent and was evident in earlier parts of sessions for performance under the smaller ratios. Response rates of 2 monkeys increased above nondrug control levels despite the putative reinforcer not being consumed during the session. When saline or a smaller dose of cocaine was substituted for 1.0 mg/kg, response rates often were suppressed below nondrug control-level responding. This suppressive effect was observed in each monkey and was more likely to be observed and/or to be of greater magnitude in large-ratio components for 3 of the 4 monkeys. When saline was administered chronically at the end of the chronic-drug phase, response rates remained suppressed in the large-ratio component for 2 of the monkeys. There was, therefore, a schedule-dependent dissociation between behavioral tolerance and the residual effects: Tolerance was greater when small ratios were arranged, whereas the residual effects were more pronounced when larger ratios were arranged.
Journal of the experimental analysis of behavior, 1991 · doi:10.1901/jeab.1991.56-345