Reinforcer magnitude attenuates: apomorphine's effects on operant pecking.
Smaller reinforcers make apomorphine side effects stronger — motivation level is a drug dial.
01Research in Context
What this study did
Scientists gave pigeons apomorphine and watched how hard they pecked a key for food.
The birds earned either one pellet or four pellets after each correct response.
They wanted to see if the size of the food reward changed how the drug acted.
What they found
The drug pushed two birds to peck faster and slowed two birds down.
When the reward was only one pellet, the drug’s punch was stronger.
The pecking looked like a side-effect of the drug, not a way to get food.
How this fits with other research
Bacon et al. (1998) saw the same push-pull pattern with morphine and hungry pigeons.
They changed hunger level; W et al. changed pellet size — both show motivation tames drugs.
Oliver et al. (2018) later used the same one-pellet trick to bring back old problem behavior.
Weinsztok et al. (2022) flipped it for kids: bigger rewards kept DRA alive when staff slipped.
Same lever — reward size — works from pigeon lab to clinic.
Why it matters
If a client’s medication suddenly changes, check the reinforcer size first.
A smaller reward can make side effects bite harder.
Keep rewards generous during med shifts and you may spare yourself new problem behavior.
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02At a glance
03Original abstract
When given to pigeons, the direct-acting dopamine agonist apomorphine elicits pecking. The response has been likened to foraging pecking because it bears remarkable similarity to foraging behavior, and it is enhanced by food deprivation. On the other hand, other data suggest the response is not related to foraging behavior and may even interfere with food ingestion. Although elicited pecking interferes with food capture, it may selectively alter procurement phases of feeding, which can be isolated in operant preparations. To explore the relation between operant and elicited pecking, we provided pigeons the opportunity to earn different reinforcer magnitudes during experimental sessions. During signaled components, each of 4 pigeons could earn 2-, 4-, or 8-s access to grain for a single peck made at the end of a 5-min interval. In general, responding increased as a function of reinforcer magnitude. Apomorphine increased pecking for 2 pigeons and decreased pecking for the other 2. In both cases, apomorphine was more potent under the component providing the smallest reinforcer magnitude. Analysis of the pattern of pecking across the interval indicated that behavior lost its temporal organization as dose increased. Because apomorphine-induced pecking varied inversely with reinforcer magnitude, we conclude that elicited pecks are not functionally related to food procurement. The data are consistent with the literature on behavioral resistance to change and suggest that the effects of apomorphine may be modulated by prevailing stimulus-reinforcer relationships.
Journal of the experimental analysis of behavior, 2012 · doi:10.1901/jeab.2012.98-273