Effects of chlorpromazine on fixed-ratio responding: modification by fixed-interval discriminative stimuli.
Salient schedule-correlated stimuli can enlarge chlorpromazine’s suppressive effect on reinforced responding.
01Research in Context
What this study did
Rats worked on a fixed-ratio schedule for food.
A light came on at fixed-interval moments.
The team gave chlorpromazine and watched how the light changed the drug’s bite on lever pressing.
What they found
The brighter or longer the light, the more the drug slowed the rats down.
When the light was weak or absent, the same dose hardly touched the response rate.
Schedule design, not just the drug dose, drove the size of the effect.
How this fits with other research
Kodera et al. (1976) first showed that brief lights can control pausing in fixed-interval schedules. Deitz (1986) extends that work by proving those same lights can magnify a drug’s impact.
Stretch et al. (1966) saw methylphenidate disrupt stimulus control at high doses yet spare it at low doses. The new study flips the drug class: chlorpromazine keeps its power, but only when salient stimuli are present.
Yuwiler et al. (1992) found that upcoming stimuli and past reinforcer size jointly set progressive-ratio pausing. Deitz (1986) adds that stimuli also gate how drugs alter that pause.
Why it matters
You can’t judge a medication effect without looking at the stimulus world your client lives in. A busy room, bright lights, or timed cues may boost drug side-effects on task persistence. Try running a probe session with and without salient timers or lights while keeping the contingency the same; you may see response bursts or drops that look like non-compliance but are really drug-stimulus interactions.
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02At a glance
03Original abstract
Effects of chlorpromazine (1 to 100 mg/kg) were assessed on two pigeons' responding under various modifications of a multiple schedule of food delivery. During a fixed-interval component, the first response after 5 min produced food; during the subsequent, fixed-ratio component, the 30th response produced food. Modifications of the schedule entailed changes in stimulus conditions imposed during the fixed-ratio component that did not systematically alter characteristics of performance under non-drug conditions. In the first phase of the experiment, distinctive visual stimuli were correlated with each schedule component (conventional multiple schedule); chlorpromazine produced small decreases in fixed-ratio responding (20% at 30 mg/kg). When each response during the fixed-ratio component produced the stimulus correlated with the fixed-interval schedule (fixed-interval discriminative stimulus) for 1.2 s, effects of chlorpromazine were not different from those under the conventional multiple schedule. Chlorpromazine produced greater decreases in fixed-ratio responding (55% at 30 mg/kg) when either the first response of each fixed ratio changed the stimulus correlated with the fixed-ratio schedule to the fixed-interval discriminative stimulus for the remainder of the fixed-ratio component, or when the fixed-interval discriminative stimulus was presented independently of responding according to a matched temporal sequence. When the fixed-interval discriminative stimulus was present continuously during the fixed-ratio component (mixed schedule), chlorpromazine produced even more substantial decreases in fixed-ratio responding (greater than 80% at 30 mg/kg). Effects of chlorpromazine on fixed-interval responding were also modified by the schedules of fixed-interval discriminative stimulus presentation. The effects of chlorpromazine were a joint function of the stimuli prevailing during the multiple schedule and the degree to which responding influenced these stimuli.
Journal of the experimental analysis of behavior, 1986 · doi:10.1901/jeab.1986.45-195