Auditory lateralisation: shifts in ear use during attachment in the domestic chick

Chicks were imprinted to the sound of a cluck, by differing durations of exposure in the dark on the first day of life. At test, when the chicks were placed centrally in an arena lit only by infra-red, those receiving two or three hours of exposure turned their right ear towards a source of clucks, just before approach to the source, but used their left ear instead after five or six hours exposure; after four hours there was no clear bias. This shift was not due to differences in age nor in time of day, but was a direct consequence of lengthening prior exposure. As learning about (and/or attaching to) the cluck progresses, there thus appears to be a shift from predominant use of the left hemisphere in listening and responding to the cluck. There is other evidence that the left hemisphere may be particularly involved in the chick in initial selection of important cues, while the right hemisphere elaborates relatively unselected records.