Behavior of rats under fixed consecutive number schedules: effects of drugs of abuse.
Drugs of abuse break accurate response chains, so watch for extra, mistimed steps when clients begin new meds.
01Research in Context
What this study did
Scientists gave rats a fixed consecutive number schedule. The rats had to press a lever a set number of times before a final press paid off.
They then injected the rats with drugs of abuse: morphine, cocaine, amphetamine, and phencyclidine. They watched how the drugs changed the lever-press runs.
What they found
Every drug made the rats mess up the run. The animals added extra presses, so the chain broke and fewer runs earned food.
Morphine caused the biggest, most reliable drop. Simple schedules showed the damage sooner than multiple schedules.
How this fits with other research
HEFFERLINE et al. (1963) first used fixed-number schedules in rats and saw drug-specific fingerprints. Keel et al. (1997) built on that work with the tougher fixed consecutive number rule.
Goldman et al. (1979) worked with monkeys on response chains. Both papers show abused drugs wreck sequence accuracy, but the monkey study found learning phases more fragile than steady performance. The rat data now say the same thing.
ZIMMERMAELLIOTT et al. (1962) saw amphetamine briefly scramble spaced responding, yet the rats relearned. Keel et al. (1997) show the disruption sticks under consecutive-response tasks. The gap highlights how schedule type sets how long the damage lasts.
Why it matters
If a client starts new medication, tighten your task analysis. Break long response chains into smaller chunks and give extra practice. Watch for extra, out-of-place responses—those “short runs” in rats look like extra taps, repeated words, or stalled steps in humans. Morphine-type drugs aren’t the only threat; any sedative or stimulant can do it. Probe learning early and often so you can adjust before the skill falls apart.
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02At a glance
03Original abstract
Four rats responded under a simple fixed consecutive number schedule in which eight or more consecutive responses on the run lever, followed by a single response on the reinforcement lever, produced the food reinforcer. Under this simple schedule, dose-response curves were determined for diazepam, morphine, pentobarbital, and phencyclidine. The rats were then trained to respond under a multiple fixed consecutive number schedule in which a discriminative stimulus signaled when the response requirement on the run lever had been completed in one of the two fixed consecutive number component schedules. Under control conditions, the percentage of reinforced runs under the multiple-schedule component with the discriminative stimulus added was much higher than the percentage of reinforced runs under the multiple-schedule component without the discriminative stimulus. All of the drugs decreased the percentage of reinforced runs under each of the fixed consecutive number schedules by increasing the conditional probability of short run lengths. This effect was most consistently produced by morphine. The drugs produced few differences in responding between the multiple fixed consecutive number components. Responding under the simple fixed consecutive number schedule, however, was affected at lower doses of the drugs than was responding under the same fixed consecutive number schedule when it was a component of the multiple schedule. This result may be due to the difference in schedule context or, perhaps, to the order of the experiments.
Journal of the experimental analysis of behavior, 1997 · doi:10.1901/jeab.1997.68-117