Food and amphetamine self-administration by baboons: effects of alternatives.
Cutting food access pushed baboons toward amphetamine, showing that reinforcer substitution follows economic rules.
01Research in Context
What this study did
Scientists let baboons choose between food pellets and amphetamine water. They tightened pellet access and raised the lever presses needed for each pellet. The team watched how often the animals worked for food versus the drug.
The study used single-case design. Each baboon served as its own control across conditions.
What they found
When pellets were easy to get, the baboons mostly ate and ignored the drug. When pellet access was cut, the same animals switched and drank more amphetamine. The drug stepped in as a substitute only when food became scarce.
Raising the lever presses needed for pellets lowered food intake for every animal. Fluid intake went up for some but not all, showing individual differences.
How this fits with other research
Pigott (1987) looked like a contradiction. Food satiation versus deprivation did not change total PCP intake in monkeys. The key difference is the drug: PCP versus amphetamine. PCP may not substitute for food the way amphetamine does.
Bromley et al. (1998) and Dykens et al. (1991) used similar lab set-ups with cocaine. They showed that consumption tracks unit price and that ratio size shapes tolerance. These papers support the same economic rule: cost changes behavior, whether the reinforcer is food or drug.
Au-Yeung et al. (2015) extends the idea to humans. Tokens kept kids working longer than food during extinction, just as amphetamine kept baboons working when food was tight. Conditioned or drug reinforcers can fill the gap when primary food is limited.
Why it matters
If you limit one reinforcer, clients may seek another—sometimes a harmful one. Make sure powerful backups are available before you tighten access to food, tokens, or breaks. Watch for individual swings; some clients swap reinforcers quickly, others do not. Use lean schedules only when you have safe substitutes ready.
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02At a glance
03Original abstract
The effects of the availability of an alternative reinforcer on responding maintained by food pellets or fluid solutions were examined in 6 adult male baboons (Papio cynocephalus anubis). During daily 23-hr experimental sessions, baboons had concurrent access to both food pellets and fluid, with responding maintained under fixed-ratio schedules of reinforcement that varied between the two commodities. The fixed-ratio requirement, or cost, for pellets was increased when (a) no fluid, (b) a dilute dextrose vehicle, (c) 0.002 mg/kg d-amphetamine, or (d) 0.004 mg/kg d-amphetamine was available. When given nonrestricted concurrent access to food pellets and amphetamine at minimal cost (FR 2), baboons self-administered sufficient amphetamine to decrease pellet intake. Increasing the response requirement for pellets decreased pellet intake at a similar rate regardless of the available fluid and increased fluid intake in a variable manner among baboons such that there were no statistically significant increases in fluid intake. In contrast, when access to pellets was restricted to 70% of maximal intake under nonrestricted conditions, increasing pellet cost decreased pellet intake and increased fluid intake more rapidly when the high amphetamine dose was available. Thus, amphetamine was more effective as an economic substitute for pellets when access to pellets was restricted. The response cost for vehicle and both amphetamine concentrations was increased when baboons had nonrestricted and restricted access to pellets. Increasing the response requirement for fluid delivery decreased intake of all three fluids similarly under both pellet-access conditions. The results indicate that substitution between commodities with minimal commonalities can be studied under controlled laboratory conditions and is dependent upon reinforcement schedule and commodity restrictions.
Journal of the experimental analysis of behavior, 1997 · doi:10.1901/jeab.1997.68-47