The neural mechanisms of learning and memory, particularly imprinting in the domestic chick. The young of many species, when exposed to a conspicuous object, rapidly learn the object's characteristics and subsequently narrow their social preferences to it. This learning process is called imprinting, the study of which has yielded important insights into the nature of learning and memory. A part of the chick forebrain (the IMM) has been identified as critical for imprinting. The available evidence indicates that the IMM is a site of memory for features of the imprinting stimulus. Currently, learning-specific changes in the IMM are being studied using behavioural, biochemical, electrophysiological and immunocytochemical techniques.