Predispositions and learning: behavioural dissociations in the chick

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In young domestic chicks, Gallus gallus domesticus, the formation of filial preferences involves at least two processes: a learning process through which chicks come to recognize the features of certain stimuli to which they are exposed and a predisposition to approach stimuli resembling conspecifics. The predisposition becomes manifest as an increasing preference for a rotating, stuffed adult fowl over a rotating red box. This change over time occurs even in chicks that have been trained by exposure to the red box. The present experiment confirmed the latter result, and also showed that preferences did not change over time when they were measured in tests involving the familiar red box and a novel, striped blue box. Furthermore, when chicks were trained with the red box after a sensitive period for the development of the predisposition had elapsed, preferences did not change with time of testing, but were determined by learning only. The results rule out an interpretation of earlier findings in terms of stimulus-dependent differential forgetting. They suggest that the mechanism underlying learning is separable from the mechanism underlying the predisposition.