Ubiquity of schedule-induced polydipsia.

Spaced feeding of individual food pellets to food-deprived rats induced excessive drinking after pellet delivery if water was continuously available. When access to water was restricted to a portion of the inter-pellet interval, and competition from food-reinforced bar pressing was removed, excessive drinking occurred whenever drinking was possible. This finding extends the generality of accounts of excessive behavior that implicate induction by apparently unrelated scheduling characteristics of the environment.