A hallmark of human brain function is cerebral lateralization and specialization. This specialization necessitates an efficient interhemispheric communication system. No other mammal possesses the degree of localization of function seen in the human. Only the human brain has the intellectual and computational capabilities necessary to study how neural systems both generate and respond to the intense information demands of the environment.

At first glance the anatomical brain appears largely symmetrical. More careful analysis reveals “typical counterclockwise hemispheric torque,” which is reflected in the fact that the left parieto-occipital region is wider and extends further posteriorly than the right. On the right side the frontal lobe is larger than the left and extends further anteriorly (Glicksohn and Myslobodsky, 1993). This difference is called petalia (Hadziselimovic and Cus, 1966). Fiber bundles interconnect the left and right sides. It must be assumed that these bundles play a role in the behavioral specializations that are reflected in the laterality of behavior.