Functional cerebral asymmetries are a universal phenomenon
(Rogers and Andrew, 2002). Theories trying to explain the
ontogenetic events leading to adult lateralised brain patterns in
humans and other animals can be broadly labelled either genetic
or epigenetic. While genetic theories propose that the intergenerational
transmission of cerebral asymmetries is directly
controlled by genetic factors (McManus, 2002), epigenetic theories
assume that the initial neural pattern is largely symmetric
(Previc, 1991). However, it develops into an asymmetric
form by lateralised factors interfering during ontogeny. Avian
visual lateralisation is currently the best example available for
an explanation of the development of asymmetrical brain functions
that stresses the interaction of genetic and epigenetic
factors.