A quantitative interresponse-time analysis of DRL performance differentiates similar effects of the antidepressant desipramine and the novel anxiolytic gepirone.
Check IRT shapes, not just rates, to see if a drug really improves DRL timing or just spreads responses out.
01Research in Context
What this study did
The team ran a 72-second DRL schedule. Animals had to wait at least 72 s between presses to earn food.
Two drugs were tested: the antidepressant desipramine and the new anxiolytic gepirone. The computer recorded every pause between responses so the researchers could see exactly how timing changed.
What they found
Desipramine made the animals press more slowly and smoothly. The pauses shifted as a tidy group toward the 72-s target.
Gepirone also raised reinforcement, but it did so by scattering the pauses. The timing pattern looked more random, not a clean shift.
How this fits with other research
Brinker et al. (1975) showed that, without drugs, pigeons can line their pauses up almost perfectly to any DRL value. The new study adds that drugs can mimic that good performance in two very different ways.
Hart et al. (1974) found that tightening the DRL requirement cuts responding and boosts wheel running. The present paper keeps the requirement fixed and shows that drugs, not schedule changes, can also reshape the same pause distribution.
Langford et al. (2021) gave an anxiolytic and saw less pausing when conditions got worse. Here, gepirone (another anxiolytic) changed pause shape rather than pause length, revealing another lever by which anti-anxiety drugs can alter timing.
Why it matters
When a client on medication suddenly starts earning more DRL reinforcers, do not assume the med simply "slowed them down." Plot the interresponse times. A smooth shift means true timing improvement; a scattered blob means the drug is just making responding irregular. That picture tells you whether to keep, adjust, or fade the med.
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Join Free →Print the last session’s IRT histogram; if the peak moved cleanly to the DRL value, keep the med dose—if the bars just flattened, call the prescriber.
02At a glance
03Original abstract
We describe an interresponse-time analysis of performance on a differential-reinforcement-of-low-rate 72-s schedule. This analysis compares the obtained interresponse-time distribution of individual rats to a corresponding random interresponse-time distribution. The random interresponse-time distribution is a negative exponential probability function; it predicts the relative distribution of interresponse times if the rat emitted the same number of responses randomly (i.e., with a constant probability) with respect to time. The analysis provides quantitative measures of peak location and dispersion of the interresponse times toward random performance. In Experiment 1, an unexpected outcome of this analysis was that the rats would have obtained more reinforcers had they responded at the same rate but randomly. Based on the interresponse-time analysis in Experiment 1, it was shown that rats trained on the differential-reinforcement-of-low-rate 72-s schedule could increase the number of reinforcers obtained in two ways: first, by a coherent shift of the interresponse-time distribution toward longer durations and, second, by dispersal of the interresponse times toward a random interresponse-time distribution. Experiment 2 applied the analysis described in Experiment 1 to the effects of desipramine and gepirone. Both drugs decreased response rate and increased reinforcement rate, but their effects on the distribution of interresponse times were different. The increase in reinforcement rate observed with desipramine was accompanied by a coherent shift of the reinforcement rate observed with gepirone was accompanied by dispersal of the interresponse-time distribution toward the random negative exponential prediction.
Journal of the experimental analysis of behavior, 1991 · doi:10.1901/jeab.1991.56-173