Lateralization in Its Many Forms, and Its Evolution and Development

Lateralization of the central nervous system and side biases in behavior are much more common than once thought and it now seems that they are so widespread that it may be symmetry, rather than asymmetry, that demands an explanation. This chapter discusses examples of lateralization in vertebrates and invertebrates. It summarizes research on the development of lateralization in two model species and presents a gene-environment perspective, including the influence of hormones on the development of lateralization. It then considers evidence indicating why lateralization evolved, and does so from the perspective of both the lateralized individual and the lateralized population. After discussion about the likelihood that preferred use of one limb (hand) over the other is an unreliable indicator of the presence/absence of hemispheric specialization (viz., absence of handedness does not necessarily mean absence of hemispheric lateralization), association between brain lateralization, limb preference and temperament is given some special attention.