The split brain research of several decades ago sparked many educators' interest in our brain's organization. The hemispheric separation of selected cognitive functions made sense to teachers who had long observed personality and ability differences in developing brains. Although the right-brain/left-brain rhetoric and learning styles inventories that emerged often went far beyond what neuroscientists had discovered, they continue to affect educational beliefs and practice.

Subsequent spectacular advances in imaging technology allowed scientists to closely examine specific hemispheric subsections in normal brains, and their discoveries led to the prevailing modular theory of brain organization. Simply stated, modularity means that our brain is composed of a large number of subsystems that process distinct functions (such as tone recognition), and these subsystems often combine to process related more complex tasks (such as word recognition and language comprehension and production).

Thus, at the hemispheric level, the left hemisphere (in most people) was believed to be specialized to process language, since people with left hemisphere damage suffer specific language deficits. But if processing language is the defining purpose of the primate left hemisphere, what purpose does it serve in non-human primates, species that don't have a grammatical language?

In his marvelous new book, The Executive Brain: Frontal Lobes and the Civilized Mind, the renowned scientist Dr. Elkhonon Goldberg proposes a different perspective on modularity and brain organization. He argues that the hemispheric location of a cognitive function, such as language, is merely a special consequence of a more fundamental principle of primate brain organization.