Hemispheric Lateralization

Hemispheric Lateralization Prenatally

Hemispheric lateralization is observable from a relatively early prenatal stage, with asymmetry being evident from around 21 weeks’ gestation. The Geschwind–Galaburda theory, developed in the 1980s, suggested that prenatal exposure to hormones, and testosterone in particular, influences the development of the cerebral hemispheres. They suggested that each hemisphere matures at different rates and that this development is influenced by the levels of testosterone in the body, causing a delay in left hemisphere development and a more rapid development of the right hemisphere. It is argued that this can explain why sex differences are sometimes observed in the hemispheric lateralization of adults, with males tending to be more strongly lateralized and females tending to be more bilateral.

Hemispheric Lateralization Through Childhood

A number of different research labs have looked at how hemispheric lateralization develops through childhood, and generally the findings have been quite consistent. Younger children tend to be more bilateral, although right hemispheric superiority for the processing of emotional faces in children has been found as early as 5 years. This hemispheric lateralization for the processing of emotional faces then continues to develop and increase through to around 10–12 years of age, at [Page 1042]which point relatively adult-like patterns of lateralization can be observed. Further, this increasing strength of lateralization for the processing of emotive faces is correlated with the increasing ability of children to process emotive information, such as discriminating between different expressions of facial emotion. Therefore, children with more strongly lateralized brains may be more effective at processing emotional stimuli.

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