Factors Influencing Development of Lateralization

The influence of experience in early life on the later expression of lateralized brain structure and behaviour has long been known although it is presently given less attention than is the genetic determination of lateralization. The aim of this paper is to show that research on two animal models, the chick and the rat, has revealed that the expression of some types of lateralization is entirely dependent on certain kinds of stimulation of the developing animal, as well as on the hormonal condition of the animal at the time of that experience. Thus a range of phenotypes, from symmetrical to strongly asymmetrical, may develop in response to early life events involving, in particular, parent-offspring interactions.