Over the past ten or so years, brain plasticity has become an extremely hot scientific trend and a huge commercial enterprise. From the parent who wants to give his or her newborn an enriched environment to promote superior brain growth to the aging adult who wants to stave off Alzheimer's disease, exercising, enriching, and training the brain has become a multimillion-dollar industry. Hundreds of brain promotion companies have sprouted up, such as The Baby Einstein Company, LLC, and hundreds of new books are published each year on brain enrichment. “Brain health,” “brain training,” and “brain fitness” are terms that are bandied about in the advertising world, suggestive of the possibility of improving and prolonging intellectual health. However, this “brain improvement” commercialism, although occasionally overstated, is not without some foundation in hard science: the discovery of brain plasticity.

The roots of the concept of “brain plasticity” can be traced toWilliam James's seminal work, The Principles of Psychology (1890), in which he clearly understood that behavior, habits, or instincts are governed by certain physiological limitations. He states, “Plasticity, … in the wide sense of the word, means the possession of a structure weak enough to yield to an influence, but strong enough not to yield all at once.… Organic matter, especially nervous tissue, seems endowed with a very extraordinary degree of plasticity of this sort; so that we may without hesitation lay down as our first proposition the following, that the phenomena of habit in living beings are due to the plasticity of the organic materials of which their bodies are composed” (p. 106).

When we look at our environment, we immediately detect and recognize they objects, buildings, and people surrounding us. Our perception of fine detail, lines, edges, color, movement, and depth are all important for building up representations of these objects, scenes, and people. This processing occurs rapidly and is achieved effortlessly by the visual system as we take in the world with both eyes. Imagine what it might be like to not have vision through two eyes – to be completely blind. We would have to use our remaining intact sensory systems to their fullest capacity in order to interact with the world. Our senses of touch, taste, smell, and hearing would become significantly more important to allow us to connect with and understand our world.

Now instead, consider what it might be like to lose vision in only one eye. With one completely nonfunctional eye and one intact eye, our visual system would still receive light input through the intact remaining eye. So, one might ask, how could having only one eye affect our ability to see? From a systems point of view, the physical light input to our visual system would be reduced by half compared to the intact binocular visual system.