Biomedical subjects

J S Macdonall

Publications and source records attributed to J S Macdonall.

3 recordsLinked to original sources

PubMed1988

Concurrent variable-ratio schedules: Implications for the generalized matching law.

Rats' responses were reinforced on concurrent variable-ratio variable-ratio schedules in which responses on one lever incremented the ratio counter and responses on a second lever changed the schedule and correlated stimulus. The relative frequency of reinforcement was varied from .10 to .99. In one set of conditions, responding on the main lever incremented both ratio counters, but reinforcement required a response in the presence of the stimulus correlated with the ratio that had been completed. In a second set of conditions, responses on the main lever incremented only the ratio correlated with the stimulus that was currently present. When main-lever responses incremented both ratio counters, subjects distributed responding and time in a manner consistent with the generalized matching law. When responses on the main lever incremented only the schedule currently in effect, the rats responded almost exclusively on the schedule producing the higher frequency of reinforcement. These results extend the applicability of the generalized matching law to dependent ratio schedules.

Journal Article↗

PubMed1979

Increasing the rate of ethanol consumption in food- and water-satiated rats.

The effects of food satiation, ethanol concentration, and the schedule of ethanol availability on the rate of ethanol consumption were investigated in rats. In Experiment 1 separate groups were exposed to 6.2 or 12.5% w/v ethanol and unlimited access to food. The food and ethanol were available concurrently for one to three hours daily. After approximately 15 sessions unlimited food was available whenever ethanol was not available. The rate of ethanol consumption was positively related to ethanol concentration and negatively related to duration of ethanol availability. In Experiment 2 similar procedures were followed, except rats had unlimited access to food throughout the experiment. The results were similar to Experiment 1. In Experiment 3 separate groups were exposed to 6.2 and 12.5% w/v ethanol for one hour every other day; unlimited food was available throughout the experiment. The results were similar to the one-hour availability groups in Experiments 1 and 2. In all experiments ethanol consumption rates increased to levels above baseline and above the usual ethanol metabolic rate found in rats. The results demonstrated new combinations of ethanol availability and non-availability durations that were sufficient to significantly increase the rate of ethanol consumption.

Alcohol Drinking↗

PubMed1977

A molecular analysis of multiple schedule interactions: negative contrast.

The present experiments investigated the relationship between changes in the relative reinforced interresponse-time distributions and the occurrence of positive and negative contrast in multiple variable-interval-variable-interval and multiple variable-interval-extinction schedules of reinforcement. Experiment I demonstrated that changes in the interresponse-time distributions were consistently correlated with response-rate changes referred to as positive and negative contrast. Corresponding changes in the reinforced interresponse-time distributions suggested that negative contrast resulted as an inductive effect of selectively reinforcing long interresponse times in the altered component at the moment the baseline schedule was reintroduced. Experiment II demonstrated that the magnitude of the negative-contrast effect could be significantly decreased if the altered component schedule was modified in order to prevent the reinforcement of these interresponse times during the first few sessions of baseline recovery. The results supported a proposal that interresponse time-reinforcer relations may act as amplifiers or attenuators of negative contrast.

Journal Article↗