A Pheromone That Rapidly Promotes Learning in the Newborn

Abstract

Mammalian neonates depend on their mother's food supply and use a defined sequence of actions to find her mammary area. Their behavior is initially uncertain and demanding but rapidly becomes optimal. Efficient learning is thus operating in newborns. For instance, European rabbit (Oryctolagus cuniculus) pups localize the nipples through typical orocephalic movements. These movements are released by the mammary pheromone secreted in milk or by prenatally learned odor cues. During daily nursing, they also learn odors associated with the mother, supposedly with sucking as the main reinforcer. We here investigate the role of the mammary pheromone as an enforcer of early olfactory learning in newborn rabbits. In testing more than 950 pups, we show that the mammary pheromone promotes learning of neutral odorants paired with the pheromone in single and short trials. The pheromone-induced learning is efficient from birth and supports successive acquisition of distinct odorants. This reveals that a mammalian pheromone can function as a "cognitive organizer" that promotes early learning of relevant environmental cues.