The nature–nurture problem revisited: in most vertebrates, early experience of certain odors, interwoven with genetically anchored developmental processes, produces lasting, often irreversible odor recognition, preferences, or avoidance. Such behavioral development often occurs during more or less defined critical windows in time. The development of responses to odors often precedes that of odor production. Neonates already orient towards odors, while many pheromones are not produced until adulthood. Even before hatching or birth, the journey of chemical communication starts in the egg or the uterus. Knowing how chemical communication and chemosensory responses to food or danger develop is essential in areas such as animal husbandry or human behavior.

Fish

Young fish are attracted to conspecific odors without prior experience. Examples are European eels, Anguilla anguilla (Pesaro et al., 1981), Arctic charr, Salvelinus alpinus (Olsén, 1987, 1990), and Atlantic salmon (Salmo salar). Kin recognition depends on early experience, as in Arctic charr. Fish reared with siblings later preferred water scented by unfamiliar siblings to water scented by non-siblings. By contrast, fish reared singly did not discriminate between water from siblings and water from non-siblings, even though they preferred sibling water to unscented tap water.