The acquisition of an appetite.

Unlike older animals, weanling-age rats do not seek water to drink when they are dehydrated, despite the fact that a physiological sensitivity to dehydration is present very soon after birth. We demonstrate here that the appetitive behaviors needed to approach and obtain water become linked to dehydration only as a result of specific postnatal learning experience. Preventing early experience with dehydration retards the developmental emergence of dehydration-induced, water-oriented behavior in young rats. But a single pairing of water with dehydration can establish an appetitive response. These findings reveal a critical role of early learning in the development of goal-oriented behavior. Such a learning process is potentially characteristic of other behavioral systems, from the most basic appetites to complex motives.