Long-term prereward suppression in monkeys unaccompanied by cardiovascular conditioning.
A tone that predicts free food can shut down monkey lever pressing for months while heart rate stays flat.
01Research in Context
What this study did
The team gave monkeys free food after a tone or light. They watched if the warning slowed the animals’ lever pressing.
Heart rate and blood pressure were tracked too. The study ran for months to see if the drop in responses lasted.
What they found
The pre-food cue cut lever pressing almost to zero. The quiet spell stayed for the whole study.
Heart rate and blood pressure did not change. Behavior dropped without any sign of autonomic conditioning.
How this fits with other research
Baron et al. (1968) also used monkeys and got the opposite heart result. Their shock-predictive cue raised blood pressure while it suppressed behavior. The new study shows free-food cues can suppress behavior without touching the heart.
Elder et al. (1973) found people could lower blood pressure on purpose with operant feedback. The monkey data say the heart is not always part of the package when cues control behavior.
Dardano (1972) showed monkeys shift choices when free food odds change. Kelly (1973) adds that even a sure free-food signal can freeze ongoing work for months.
Why it matters
You now know that signals for free reinforcement can stop operant behavior without any heart change. Check if “free” items in your setting—staff attention, iPads, snacks—are accidental cues that pause the tasks you want. You can test this by inserting a brief signal before those freebies and measuring responses before and after.
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02At a glance
03Original abstract
In Experiment I, a 3-min tone that preceded a free pellet of food suppressed variable-interval performances maintained by the same type of pellets, but failed to elicit conditioned changes in the heart rates and blood pressures of two rhesus monkeys. Initially severe, the prereward suppression became temporally discriminated to progressively later portions of the tone, and was maintained at an attenuated level for over four months. The suppression was apparently not caused by interfering autonomic respondents, nor was it superstitiously conditioned, since 21 of the initial 25 tone-food pairings took place outside of baseline sessions. In Experiment II, a 1-min light, paired with four free pellets of food, suppressed the variable-interval responding of a second pair of similarly trained monkeys. An interresponse-time analysis showed that in one subject, mild prereward suppression of responding developed through two stages. On early trials, response rate slowed by 10% throughout the prefood interval. On later trials, the animal suppressed by pausing for a like portion of the interval, most often near the end, but otherwise responded normally during the prefood signal.
Journal of the experimental analysis of behavior, 1973 · doi:10.1901/jeab.1973.20-93