Perception of odor blending mixtures in the newborn rabbit

In adult mammals, the processing of complex odor mixtures is elemental or configural. Here, we challenged these processes in newborn rabbits, in evaluating their perception of a binary odor mixture for which perceptual blending occurs in humans. This model of newborn animal was interesting since general questions remain on how odor cues are processed in immature organisms, and since rabbit pups present abilities of rapid odor learning. In the present study, we first demonstrated (Exp. 1) that rabbit pups rapidly acquired the odor of the binary mixture through associative conditioning (when the mammary pheromone was used as unconditioned stimulus). Then, we compared how they responded to the mixture, its components and the mammary pheromone, after they had learned the mixture or one of its constituents. After they had learned the odor of the mixture, they responded to its odor and the odor of its constituents (Exp. 2). However, after they had learned one constituent's odor, they responded to this odor but not to the mixture's odor (Exp. 3). The response to the mixture appeared nevertheless when pups successively acquired the odor of the two components (Exp. 4). Therefore, both elemental and configural processing of the mixture seem to be displayed by rabbit pups, suggesting that neonatal perception of a simple odor mixture may involve more than the perception of its constituents.