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The literature was searched for information about the local rates of responding and reinforcement during concurrent schedules. The local rates of reinforcement obtained from the two components of a concurrent schedule were equal when a long-duration changeover delay was used and when many sessions were conducted, except when the two components provided different simple schedules. The local rates of responding were equal under some conditions, but they differed when one component provided a ratio and the other an interval schedule. Across schedules, local rates of reinforcement changed with changes in the schedule of reinforcement. Local rates of responding did not change with changes in change-over-delay duration but did with changes in the changeover ratio and with changes in the programmed rates of reinforcement. The results generally conform to the Equalizing and Melioration Principles and help to clarify current statements of the Matching Law. The results also suggest that changes in the local rates of responding and reinforcement may be orderly across schedules.

Male Fischer 344 rats were examined for an age-dependent sensitivity to the anticonflict and central nervous system (CNS) depressant effects of diazepam. A conflict paradigm was used to measure the ability of single intravenous injections of diazepam to attenuate punishment-induced suppression of behavior and to elicit CNS depression in young, mature, and senescent rats. Senescent rats had the lowest behaviorally active threshold dose. However, diazepam at the behaviorally active threshold dose produced a simultaneous increase in punished and unpunished responding in all three age groups. Punished responding was increased more and over a wider dose range in the young and mature rats than in the senescent rats. Sensitivity to the CNS depressant effects of diazepam was over four times greater in the senescent rats than in the other two age groups. In summary, the results indicate that the behavioral effects of diazepam vary with dosage and age of the rat. The male Fischer 344 rat may be a useful animal model for exploring how diazepam elicits age-related behavioral effects in humans.

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