Experiential canalization of behavioral development: results

In exploring the possible experiential canalization of development, it was found that the mallard duck embryo's contact call plays a canalizing role in species-specific perceptual development. When mallard ducklings were prevented from hearing the contact call, they were susceptible to developinga preference for an extraspecific maternal call over the mallard maternal call. Exposure to the contact call prevented the ducklings from developing a preference for the extraspecific maternal call. Thus, normally occurring experience, in concert with genetic and other activities, can canalize behavioral development. Canalizing influences account for developmental stability, so that what we think of as normal or typical for a species repeats itself generation after generation. In order for evolution to occur, through genetic mutation or otherwise, the canalizing influences associated with normal development must be overcome. Canalization is thus a conservative feature of development that prevents evolution from occurring in a ready fashion. My preced ing article (Gottlieb, 199 la)established the theoretical framework for examining the possibility that normally occurring experience can canalize behavioral development. The present article presents empirical evidence for the experiential canalization of species-specific maternal attachment. The present hypothesis is that normally occurring experience helps to achieve species-specific development by making the developing organism unresponsive to extraspecific influences. For example, if the mallard duck (Anas platyrhynchos) embryo is devocalized, the usually highly selective response to the mallard maternal call is weakened: After hatching, the duckling is as responsive to a chicken (Galfus gallus) maternal call as to a mallard maternal call in a simultaneous-choice test (Gottlieb, 1978). Exposing otherwise devocalized embryos to a recording of mallard embryo contact vocalizations causes them to show the usual preference for the mallard call versus the chicken call in the postnatal test (Gottlieb, 1985). Exposure to other types of sibling vocalizations in embryo, or exposure to the contact call after hatching, is ineffective, so the kind of experience and the timing of the experience are highly specific. If the experiential canalization hypothesis is correct, embryonic devocalization should make the mallard embryo and hatchling more susceptible to exposure to an extraspecific maternal call, assuming that the contact vocalization is acting as a canalizing or buffering experience. With the necessary control groups, five experimental conditions are necessary to test the canalization hypothesis, as indicated in Table 1. In Table 1, X indicates the predicted preference and X—-X indicates prediction of no preference. The two most critical