Imprinting: The Interaction of Learned and Innate Behavior

Julian Jaynes, Dissertation Abstracts International, 1978, 38, 7, 3458.

Excerpt: In the anatomical development of the embryo, there exist precise critical periods in which specific tissues are susceptible to environmental influences acting at that time but at no other, the fate and future of the tissue being fixed thereafter (9). It is now apparent that similar critical periods exist in behavioral development also—specific stages in ontogeny during which certain types of behavior normally are shaped with fate and molded for life, environmental influences losing effect after that time. Among insects, for example, interrace compatibility (3), host preferences in parasites (10), even color and morphology (2, 5) have, in some instances, been found to originate exclusively under environmental control during certain periods of early life. Recently, the behavioral growth of dogs has been sectioned into critical periods in which certain types of adjustments, such as emotional behavior and social responses, are thought to be fixed for the rest of life (7). And in man, the notion of discrete stages in psychosexual development and of the lasting effects of fixation at one period or another, has been found helpful in interpreting some clinical syndromes

The present study examines the critical period for filial responses in precocial birds, and the influence, on retention, of the age at which a neonate experience occurs. Previous experiments in this series (4) have revealed that domestic chicks will approach and follow an irregularly moving object shortly after exposure to it, and that this response, with no reward in the ordinary sense, increases in frequency upon further practice. Although the object to which the bird is trained can be accurately discriminated from others in a simultaneous presentation, considerable generalization occurs to strange objects during the neonatal period when such objects are presented alone