Appetitive learning in 1-day-old rat pups.

One-day-old rat pups learned to probe upward into a terry-cloth-covered paddle when they were rewarded with small infusions of milk into their mouths. In the presence of two paddles, discriminable on the basis of odor and position in the test container, the pups learned to probe into the paddle that provided them with milk. These experiments demonstrate (i) that milk may serve as a reinforcer to deprived rat pups and (ii) that pups as young as 1 day are capable of appetitive learning.