Matching law analysis of rats' alcohol self-administration in a free-operant choice procedure

The generalized matching law quantitatively describes the relation between relative response allocation and relative reinforcement allocation in a choice situation and has accounted well for drug-maintained choice behavior. Earlier studies applying the generalized matching law to alcohol-maintained choice, however, have produced somewhat atypical findings (e.g. poor fits, negative sensitivity values). These findings may be the result of the procedures used in the earlier alcohol studies (e.g. two-bottle choice procedure, variations in relative concentration of alcohol, volume consumed as dependent variable). This experiment examined the applicability of the generalized matching law to alcohol self-administration using procedures more similar to those typically used with other reinforcers. A free-operant choice procedure arranging concurrent variable-interval schedules of alcohol reinforcement was used to vary rates of alcohol deliveries produced by two response options. Results showed that the generalized matching law provided a good description of changes in the relative allocation of behavior with changes in the relative rate of alcohol delivery. Thus, the atypical results in earlier studies were likely a result of the procedures used. These results suggest that the parameters of the generalized matching law may provide useful quantitative measures of the impact biological and environmental variables on alcohol-associated choice behavior.