Simultaneous changes in behaviour and in lateralization during the development of male and female domestic chicks

Abstract

Chicks reared by a broody hen under semi-natural conditions showed sharp changes in behaviour at ages when there are sharp changes in lateralization of function in the central nervous system. On day 8 of life sustained examination of mobile objects (other than the mother) appeared suddenly and peaked. Day 8 was also the day when there was unique bias towards control of response by the visual systems fed by the right eye (‘right eye system’). On day 10 for the first time chicks began to move independently of the mother, going out of sight and further from her. On day 10 there was also a shift towards control by the left eye system, which has special interest in spatial relations of stimuli and greater ability to orient by environmental features. Female chicks remained closer to the mother, which may reflect lesser specialization of the left eye system than in male chicks. Obvious and functionally important changes in behaviour during development therefore appear to be closely linked with shifts in which eye system controls behaviour.