Instrumental learning for a thermal reinforcer in 1-day-old rats.

One-day-old rats in a cool environment (25 degrees C) quickly acquired an instrumental response when rewarded with a 20-s warming of the platform (from 25 degrees C to 36 degrees C) on which they lay. The instrumental response, turning the head to one side, was learned within 30 min after the thermal contingency began and extinguished when the contingency was reversed. This experiment demonstrates rapid operant learning by neonates in a task that does not contain a Pavlovian stimulus-reinforcer contingency. The novel experimental method has wide applicability in psychology and neuroscience.