Patterns of ethanol consumption as a function of schedule of ethanol access

The present experiment demonstrated that patterns of ethanol consumption can be controlled by altering the schedule of ethanol availability. Thirty-two male albino rats, maintained at 80% of their ad libitum weight, were first exposed to 10 base-line sessions in which access to either 8 or 32% ethanol was unrestricted. Each subject was then exposed to one of four restricted access schedules for 30 sessions. During each 23-hr session, the ethanol access period was held constant at 20 min while the time between ethanol access periods was either 70, 160, 340 or 700 min. After restricted access, all subjects were returned to unrestricted access for 10 sessions. Water was continually available throughout the experiment. When ethanol access periods occurred every 70 or 160 min, animals at both concentrations consumed more ethanol (grams per kilogram) than during the initial period of unrestricted access. When the time between ethanol access periods was 340 or 700 min, animals consumed an equal amount or half as much, respectively, as during unrestricted access. Analysis of responding revealed that the mean amount of ethanol consumed per bout was greater during restricted than during unrestricted access. The longer the time between access periods the greater the amount consumed per bout. Upon return to unrestricted access, total daily consumption increased, but the amount consumed per bout decreased to base-line level

The effect of signaled reinforcement availability on concurrent performances in humans

During Phase I, three female human subjects pressed a button for monetary reinforcement in two-component concurrent variable-interval schedules. Five different reinforcement frequencies were used in component A, whereas the reinforcement frequency in component B was held constant. Absolute rates of responding conformed to equations proposed by Herrnstein to describe concurent performances, and the ratios of the response rates and the times spent in the two components conformed to the matching law. During Phase II, the availability of reinforcement in component A was signaled by the illumination of a lamp. This resulted in suppression of response rates in component A and elevation of response rates in component B, these changes being reflected in a distortion of the matching relationship which took the form of a bias in favor of component B