Early learning and the development of filial preferences in the chick.

Newly hatched domestic chicks (Gallus gallus domesticus) rapidly form a social preference for a conspicuous stimulus to which they are exposed. The learning process involved is known as filial imprinting. When chicks are exposed to an audio-visual compound stimulus, both auditory and visual learning are enhanced. The enhancement of visual imprinting is virtually abolished when chicks are exposed separately to the auditory element, either before or after training with the audio-visual compound. Simultaneous exposure to the two elements of the compound is superior to sequential exposure in achieving the enhancement of visual learning. These results are unlike Pavlovian conditioning, but are consistent with an interpretation of imprinting as a form of within-event learning, where links are formed between the representations of the elements of the compound, that can be weakened by separate exposure to an element. Apart from imprinting, chicks may show a developing predisposition to approach stimuli resembling conspecifics. The predisposition emerges in dark-reared chicks given some non-specific experience during a sensitive period, and is expressed as a relatively general preference for stimuli with a head and neck region. In the natural situation, the animal's response may be biased by the predisposition, and through imprinting it then learns the characteristics of individuals.