Instinct

An instinct is a stereotyped, species-typical behavior that appears fully functional the first time it is performed, without the need for learning. Such behaviors are usually triggered by a particular stimulus or cue, and are not readily modified by subsequent experience. For instance, a kangaroo rat instantly performs an automatic escape jump maneuver when it hears the sound of a striking rattlesnake, even if it has never encountered a snake before. Clearly, instinctive behaviors play an important role in survival, but our understanding of the forces that promote and guide their development in living animals is in fact quite limited.

Imprinting

In another classic study of instinctive behavior, ethologist Konrad Lorenz showed that baby ducks and geese, which are observed to closely follow their mother on their early forays away from the nest, could also be induced to follow a substitute. The baby birds would form an attachment to whatever individual was present as they opened their eyes and moved about after hatching, regardless of that individual's species identity. Young birds that had thus imprinted on Lorenz followed him everywhere as they matured, and as adults, these birds were observed to court humans, in preference to members of their own species.

Lorenz concluded that imprinting represented a kind of preprogrammed learning, guided by a mechanism that under normal circumstances would not be corrupted by individuals of the wrong species. In the natural situation, imprinting would facilitate the babies' social attachment to their mother, which later allows them to recognize appropriate mating partners.

Critical periods

Bird song is a largely species-specific behavior performed by males in their efforts to establish and maintain their territories and to attract females. Many songbirds develop their mature songs through a process involving a critical period when, as a nestling, the bird hears the song of its father. The juvenile bird does not sing until the following spring, when it begins to match its immature song to the one it heard from its father during its critical period. If the nestling is prevented from hearing adult song during the critical period, it will never develop a species-typical song. Evidently, there is also a strongly instinctive aspect to what may be learned during the critical period; most birds cannot produce every song heard during that time, but appear to be selective toward songs that are produced by other members of their species.