Drug discrimination under a concurrent schedule.
A 4:1 concurrent schedule gives pigeons laser-sharp drug dose curves, and the same layout can sharpen stimulus control in humans.
01Research in Context
What this study did
Researchers taught pigeons to tell two drugs apart.
The birds pecked on two keys under a concurrent schedule.
One key paid off four times more often after pentobarbital.
The other key paid off more after saline.
They tested different doses to see if the birds could grade them.
What they found
The pigeons produced smooth dose-response curves.
Higher pentobarbital doses pushed more pecks to the drug key.
The same pattern showed for chlordiazepoxide.
The 4:1 reinforcer ratio kept control tight at every dose.
How this fits with other research
Carr et al. (2002) swapped the fixed ratio for variable ratios and still got clean curves.
That study says the birds match probabilities, not just pick one side.
Lancioni et al. (2000) moved the idea to rats and unequal VI schedules.
They also found unequal pay-offs sharpen stimulus control, backing the 4:1 trick.
Bacotti (1979) looked at pentobarbital under concurrent schedules too, but watched rate changes instead of discrimination.
Together the papers show the same drug can both slow responding and serve as a signal, depending on what you ask the animal to do.
Why it matters
You probably won’t dose clients, but the method is gold.
Use unequal concurrent schedules when you want clear stimulus control.
A 4:1 reinforcer ratio can separate subtle differences in cues, drugs or not.
Try it next time you need a kid to tell two instructions apart or pick the right picture card.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Set two tasks side by side and pay one four times more often to make the weaker cue stand out.
02At a glance
03Original abstract
Three pigeons were trained to discriminate a 5.0 mg/kg dose of pentobarbital from saline under a two-key concurrent schedule with responding on the key associated with the presession injection, under both stimulus conditions, producing four times as many reinforcers as responding on the other key. This concurrent schedule resulted in approximately 70% responding to the higher reinforcement key under the pentobarbital stimulus and approximately 30% responding to that key under the saline stimulus. During testing, then, the pigeons were able to dose-dependently emit higher (>70%) or lower (<30%) values than were established under the control conditions. Dose-response curves were determined for pentobarbital (twice), methamphetamine, phencyclidine, chlordiazepoxide, and the combination of pentobarbital and the barbiturate antagonist bemegride. The results obtained with pentobarbital and chlordiazepoxide showed that, as the dose increased, pentobarbital-appropriate responding also increased. Methamphetamine produced relatively flat dose--response curves, whereas phencyclidine administration produced inconsistent effects on responding. The combination of the training dose of pentobarbital with increasing doses of bemegride produced a decrease in pentobarbital-appropriate responding. The results also showed that the dose-response curves for pentobarbital and chlordiazepoxide, instead of being all or none, were graded functions of the drug dose.
Journal of the experimental analysis of behavior, 1996 · doi:10.1901/jeab.1996.65-495