Efficiency and persistence of licking in rats.

Thirsty rats tested in 60-min sessions licked an empty spout for access to a water spout. We raised the behavioral price of the water lick by requiring more licks at the empty spout per lick at the water spout. At relatively high prices the rats made relatively few water licks but licked more efficiently, getting more water per lick. Controls showed that the rise in efficiency with price was not attributable to two variables previously confounded with price: the total number of water licks, and the temporal pattern of access. At a higher price the rats also licked more persistently, making more extra water licks before the shutter could occlude the spout. However, yoked controls showed that the greater persistence resulted not from price, but from the relatively stringent pattern of access that accompanied the higher price. Extra water licks diminished as the session progressed, apparently from satiety, not fatigue. The results have implications for behavioral ecology, behavioral economics, motivation, and the methodology of reward.