Behavioral economics of concurrent ethanol-sucrose and sucrose reinforcement in the rat: effects of altering variable-ratio requirements.
Ethanol demand in rats stays stubbornly high even when response requirements climb, and ethanol readily substitutes for sucrose when sucrose gets expensive.
01Research in Context
What this study did
The team let rats choose between two levers. One lever gave ethanol mixed with sugar. The other gave plain sugar.
They kept raising the number of presses needed for each lever. They wanted to see how hard the rats would work for each drink.
What they found
Rats barely cut their ethanol-sugar drinking even when the cost jumped. Plain sugar drinking dropped fast.
When plain sugar became expensive, rats switched to the ethanol-sugar lever. Ethanol acted like a backup reinforcer.
How this fits with other research
Vaughan (1985) saw the same swap in monkeys. When sweet saccharin got cheaper, the animals chose it over PCP. Both studies show drug intake falls if a sweet alternative is easy to get.
Cryan et al. (1996) looks like a contradiction at first. They raised bar-press costs for food and water and found the two went down together—no substitution. The difference is commodities: food and water are daily needs, so rats treat them as a package. Ethanol and sugar are luxuries, so rats can trade one for the other.
Kearns (2025) folds all these rat drug-choice studies into one story. The review says price, income, and reinforcer type usually predict choice, but exceptions like the ethanol-sugar swap warn us that drugs can still hold their value.
Why it matters
For your clients, this means a powerful backup reinforcer can edge out a problem behavior, but only if the backup is truly easier to get. If the client’s "ethanol" is screen time or junk food, raise its cost (effort, wait time) while making the healthy option cheap and fast. Watch for stubborn behaviors that stay inelastic—those need extra layers like response blocking or satiation.
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02At a glance
03Original abstract
These experiments examined the own-price and cross-price elasticities of a drug (ethanol mixed with 10% sucrose) and a nondrug (10% sucrose) reinforcer. Rats were presented with ethanol-sucrose and sucrose, both available on concurrent independent variable-ratio (VR) 8 schedules of reinforcement. In Experiment 1, the variable ratio for the ethanol mix was systematically raised to 10, 12, 14, 16, 20, and 30, while the variable ratio for sucrose remained at 8. Five of the 6 rats increased ethanol-reinforced responding at some of the increments and defended baseline levels of ethanol intake. However, the rats eventually ceased ethanol-reinforced responding at the highest variable ratios. Sucrose-reinforced responding was not systematically affected by the changes in variable ratio for ethanol mix. In Experiment 2, the variable ratio for sucrose was systematically increased while the ethanol-sucrose response requirement remained constant. The rats decreased sucrose-reinforced responding and increased ethanol-sucrose-reinforced responding, resulting in a two- to 10-fold increase in ethanol intake. Experiment 3 examined the substitutability of qualitatively identical reinforcers: 10% sucrose versus 10% sucrose. Increases in variable-ratio requirements at the preferred lever resulted in a switch in lever preference. Experiment 4 examined whether 10% ethanol mix substituted for 5% ethanol mix, with increasing variable-ratio requirements of the 5% ethanol. All rats eventually responded predominantly for the 10% ethanol mix, but total amount of ethanol consumed per session did not systematically change. In Experiment 5, the variable-ratio requirements for both ethanol and sucrose were simultaneously raised to VR 120; 7 of 8 rats increased ethanol-reinforced responding while decreasing sucrose-reinforced responding. These data suggest that, within this ethanol-induction procedure and within certain parameters, demand for ethanol-sucrose was relatively inelastic, and sucrose consumption was independent of ethanol-sucrose consumption. Demand for sucrose, on the other hand, was relatively elastic, and ethanol-sucrose readily substituted for it. The results are discussed in terms of applying a behavioral economic approach to relationships between drug and nondrug reinforcers.
Journal of the experimental analysis of behavior, 1995 · doi:10.1901/jeab.1995.64-331