A parametric evaluation of the hedonic and motoric effects of drugs: pimozide and amphetamine.
Pimozide cuts both movement and reward value, while amphetamine boosts reward before it boosts movement—use this lens when meds change client work rates.
01Research in Context
What this study did
The team gave rats two drugs: pimozide and amphetamine.
They watched how fast the rats pressed a lever for food.
They also checked how much of the pressing was truly for the food reward.
What they found
Pimozide slowed the rats down and made food less rewarding.
Amphetamine sped the rats up and made food more rewarding.
Higher doses changed both speed and reward value, but in different ways.
How this fits with other research
Goldman et al. (1979) saw d-amphetamine hurt learning more than simple pecking.
The new study adds detail: the drug boosts reward strength, but only if the animal can still move.
WALLER et al. (1962) found amphetamine raised suppressed pecking.
Our study shows that rise could come from stronger reward, not just more motor drive.
Northup et al. (1991) later used progressive-ratio schedules and saw cocaine push harder than food.
Our dose-response curves help explain why: stimulants steepen the reward curve before motor limits kick in.
Why it matters
When a client on antipsychotics works less, you can now ask: is the drug dulling the reward or slowing the body?
Check both rate and breakpoint. If rate drops but breakpoint holds, motor side effects may be the main culprit.
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02At a glance
03Original abstract
This study uses a curve-fitting approach to evaluate the effects of drugs on reinforced responding in rats. The subjects obtained reinforcement according to a series of five different variable-interval schedules (a five-component multiple schedule). For each rat, pimozide, a neuroleptic, decreased response rate, and the decrease was associated with (1) a decrease in the estimated asymptotic response rate and (2) an increase in the rate of reinforcement necessary for half-asymptotic responding. That is, pimozide decreased the proportion of responding maintained by a given rate of reinforcement. In contrast, intermediate doses of amphetamine increased response rate and increased the proportion of responding maintained by a given rate of reinforcement. It was proposed that the response rate asymptote indexes motor capacity, and the rate of reinforcement necessary for half-asymptotic responding indexes reinforcement efficacy; accordingly, pimozide decreased motor capacity and reinforcement strength and amphetamine increased reinforcement strength.
Journal of the experimental analysis of behavior, 1983 · doi:10.1901/jeab.1983.40-113