Developmental Analysis of Schedule-Induced Polydipsia

In a developmental analysis of schedule-induced polydipsia (SIP), 8 female, albino rats were exposed to either a FI-60-sec. or a VI-60-sec. reinforcement schedule with 4 Ss in each group. Results indicated that the adventitious reinforcement explanation for SIP is not tenable, since licks did not occur with equal probability in all periods of the interpellet interval during SIP development; lick bursts coming in contact with pellet deliveries were a result rather than a cause of SIP; and SIP developed more slowly on the VI than on the FI schedule.

Acquisition and Extinction of Schedule-Induced Polydipsic Consumption of Alcohol and Water

16 Charles River (cd) rats were trained to bar-press on an FI 60 schedule for varying number of days, half with water present and half with alcohol. Predictably, schedule-induced fluid consumption resulted. 10 days of extinction of bar-pressing followed. During FI 60 both groups bar-pressed approximately equally often but greater fluid consumption occurred in the group on water. During extinction, both groups showed reduced bar-pressing behavior. Whereas water consumption was extinguished in two days, alcohol consumption remained high and quite variable after bar-pressing had stopped. Results suggest that bar-pressing and fluid consumption are independent behaviors which finding argues against explanations of schedule-induced polydipsia based on adventitious reinforcement. For some rats, the termination of alcohol intake prior to the end of an FI 60 session without an associated cessation of bar-pressing suggested that schedule-induced polydipsia may have been a function of the aversiveness of the reinforcement schedule.