Food deprivation and food-delay effects on the development of adjunctive drinking.

Twelve rats were food-deprived to 90% or 70% of their free-feeding weights. Food pellets were then delivered every 60 s (Fixed Time 60-s schedule), and the development of adjunctive drinking was measured by the water consumed and the number of licks. For "master" rats, each lick was followed by 10-s delays in food delivery. Yoked control rats received food at the same time as their master rats and independently of their own behavior. At 70% deprivation, both master and control rats developed similar levels of schedule-induced licking, but the master rats drank less water. At 90% deprivation, master animals showed little drinking and licking, but the development of adjunctive drinking was not completely prevented. Drinking by yoked control rats did not differ as a function of deprivation level. In showing that lick-dependent delays in food delivery reduce the asymptotic development of adjunctive drinking as a function of the rats' level of food deprivation, these results support the view that environmental influences on schedule-induced drinking are modulated by motivational factors.