Drug effects on responding maintained by stimulus-reinforcer and response-reinforcer contingencies.
Pentobarbital can either raise or lower responding depending on whether the contingency is stimulus-based or response-based, while d-amphetamine usually lowers it either way.
01Research in Context
What this study did
Spealman et al. (1978) gave lab animals two kinds of reinforcement set-ups.
In one set-up, a light told the animal food was coming no matter what it did.
In the other set-up, the animal had to press a lever to get food.
The team then injected pentobarbital or d-amphetamine and watched response rates.
What they found
Pentobarbital sometimes sped responding and sometimes slowed it.
The direction depended on which set-up was in use.
D-amphetamine, in contrast, almost always slowed the animals down.
The drug did not matter which contingency was running.
How this fits with other research
One year earlier, Barber et al. (1977) saw the same flip-flop with pentobarbital.
They showed the flip depended on how fast the animal was already responding.
D et al. added a new rule: the type of contingency can also steer pentobarbital’s effect.
In 1979, V pushed the idea further by running two schedules at once.
V found pentobarbital still changed rates in opposite directions on each lever.
Together, the three papers say both baseline speed and schedule type guide drug effects.
Why it matters
If you ever consult on cases where clients take barbiturates or stimulants, remember this: behavior may speed up or slow down depending on the contingency you have in place. Check the reinforcement rule, not just the rate, before you blame or credit the drug.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Chart response rate before and after any med change, then note which contingency is active so you can spot drug-schedule interactions early.
02At a glance
03Original abstract
The effects of pentobarbital and d-amphetamine were assessed on key pecking by pigeons under conventional single-key multiple schedules and under two-key multiple schedules in which discriminative stimuli appeared on one key (stimulus key) while pecks on a second key (constant key) produced food. Pecks on the stimulus key had no scheduled consequences. A 60-second variable-interval schedule operated in one component of each multiple schedule: either extinction or a 60-second variable-time schedule operated in the alternate component. When the alternate-component schedule was extinction, a high rate of responding was maintained in the variable-interval component of the single-key schedule; responding on both keys was maintained in the variable-interval component of the two-key schedule. Pentobarbital increased responding in the variable-interval component of the single-key schedule and increased stimulus-key, but not constant-key responding in that component of the two-key schedule. When the alternate-component schedule was changed to variable time, responding declined in the variable-interval component of the single-key schedule; stimulus-key responding was no longer maintained under the two-key schedule. Pentobarbital decreased responding in the variable-interval component of both schedules. With an exception, d-amphetamine only decreased responding in the variable-interval component of the single- and two-key schedules both when the alternate-component schedule was extinction and when it was variable time. The results suggest that the effects of pentobarbital, but not d-amphetamine, depend on the nature of the contingency (stimulus-reinforcer, response-reinforcer) that maintains responding.
Journal of the experimental analysis of behavior, 1978 · doi:10.1901/jeab.1978.30-187