The increase of approach responses toward a bitter substance during early life is enhanced by stimulation with familiar, pre-exposed odors.

At the same time, olfaction modulates the acceptance of aversive flavors. Odors tend to be associated to contextual stimuli (such as warmth) this, in turn, enables the pups to recognize when to withdraw or approach. This sense allows newborns to develop different behaviors that will allow them to survive. Olfaction is of major importance during early stages of life in altricial species.

It is hypothesized that under the natural condition of breast-feeding, infants become familiar with the flavors consumed by their mothers, and such experiences may impact on later food and flavor acceptability and choice. They also suggest that experience with a flavor in milk alters the infant's responsiveness to that flavor during subsequent feedings. These data support the hypothesis that flavors, either consumed by the mother and transmitted to her milk or added to formula, are detected by the infant and serve to modulate feeding. This differential responsiveness to the vanilla-flavored formula was absent following these two exposures to vanilla, however. In a second test that encompassed an entire feeding, they spent more time feeding initially when the formula was flavored with vanilla. In a short-term preference test, experimentally naive infants sucked more vigorously when feeding the vanilla-flavored formula. Consistent with these findings, the bottle-fed infants' responses to vanilla-flavored formula were altered relative to their responses to the unflavored formula. Following nursing mothers' consumption of vanilla flavor, their infants breast-fed longer and consumed more milk as compared to when their mothers consumed the diluent alone.

The mammalian infant experiences a variety of flavors prior to weaning because volatile compounds, such as vanilla, are transferred from the mother's diet to her milk.

Vanilla milk