Cocaine and food as reinforcers: effects of reinforcer magnitude and response requirement under second-order fixed-ratio and progressive-ratio schedules.
Reinforcer size has a sweet spot, and cocaine keeps animals working longer than food under tough ratio schedules.
01Research in Context
What this study did
Pigeons pecked a key for two things: food pellets or cocaine. The team set up second-order fixed-ratio and progressive-ratio schedules. They varied how much of each reinforcer the birds got. They also removed brief stimuli to see how that changed pecking.
What they found
Pecking rose then fell as reinforcer size grew. This created an upside-down U. Cocaine kept birds working longer than food did. When brief stimuli disappeared, cocaine pecking dropped more than food pecking.
How this fits with other research
Moxley (2002) saw a straight drop in observing when reinforcer size shrank. The U-shape here looks like a clash, but the tasks differ: operant pecking vs. Pavlovian looking. Arroyo Antúnez et al. (2026) later showed big alternative rewards knock behavior out fast yet rebound harder. Their mouse work extends the same magnitude idea into extinction and relapse.
Halpern et al. (1966) found longer pauses as fixed ratios grew. Northup et al. (1991) add that bigger rewards first speed, then slow, overall rate. Together they tell us to split behavior into pause time and active pecks when we tweak ratio size or reward amount.
Why it matters
When you shape a new skill, start with a medium reward size. Too small kills motivation; too large can do the same. Watch for brief stimuli like praise or lights. If you remove them, clients on potent reinforcers may stall faster than those on everyday rewards. Track both pause length and active responding to spot ratio strain early.
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02At a glance
03Original abstract
Reinforcer magnitude and fixed-ratio requirement were varied under two second-order schedules. Under one, the first sequence of a fixed number of responses completed after the lapse of a 10-min fixed interval produced reinforcement. Under the second, a second-order progressive-ratio schedule, the fixed number of responses increased after each reinforcement. Either cocaine (0 to 300 micrograms/kg/inj) or food (0 to 5,700 mg/delivery) reinforcers were delivered. Under some conditions, a 2-s illumination of stimulus lights occurred on completion of each ratio sequence. Under the second-order schedule, as cocaine dose or amount of food increased, rates of responding increased; at the highest values, rates of responding decreased. Increases in the ratio requirement from 10 to 170 responses minimally decreased overall response rates. Under the second-order progressive-ratio schedule, increases in dose of cocaine or amount of food increased rates of responding; at the highest amounts of food, rates of responding decreased but response rates at the highest dose of cocaine remained relatively high. The highest ratio requirement that was completed (breaking point) depended on the dose of cocaine but was less dependent on the amount of food. Removing brief-stimulus presentations had a greater effect on completion of ratio requirements with cocaine compared to food.
Journal of the experimental analysis of behavior, 1991 · doi:10.1901/jeab.1991.56-261