Comparable Rates of Responding and Reinforcement Do Not Eliminate the Differential Effects of Ethanol on Response Chain Acquisition and Performance

Ethanol and other drugs commonly disrupt responding under repeated acquisition and performance baselines, with responding in the former condition being more sensitive to such disruption than the latter. The present study was conducted to determine if differential drug effects would occur when baseline rates of responding were comparable in the two baseline conditions. The acute effects of ethanol (0, 0.4, and 0.8 g/kg) were examined in healthy adult volunteers responding under a multiple schedule of repeated acquisition and performance of 10-response sequences. A 1-sec delay occurred after each response to keep rates of responding comparable in the acquisition and performance conditions. This delay also reduced differences in reinforcement rates between the two components. Nevertheless, responding in the acquisition condition was still more sensitive to the disruptive effects of ethanol than responding in the performance component. This differential sensitivity to ethanol was most evident in measures of accuracy of responding (e.g., percentage of errors). These findings suggest that differences in overall rates of responding and reinforcement in the repeated acquisition and performance conditions contribute little, if anything, to the differential drug effects observed on those baselines.