We have only one brain each, but our brains are neatly split down the middle into two hemispheres. Normally, these hemispheres are able to communicate with each other via a “bridge” called the corpus callosum. In the 1950s, severing this bridge was a radical surgery sometimes performed on patients with severe epilepsy that could not be treated in any other way. Neurobiologist and neuropsychologist Roger Sperry started studying the psychological effects of this treatment and came to the startling conclusion that the two halves of the brain “think” very differently.

Sperry and his colleagues discovered that the right brain takes sensory input from the left side of the body and the left brain gets its sensory input from the right side of the body. Simply by having test subjects receive sensory input from one eye and then the other, the researchers were able to learn how the two sides of the brain interpret sensory input.

Basically, the left side of the brain is the logic centre while the emotions are processed in the right hemisphere. Normally, the two halves of the brain work together, but when the bridge between them is severed, they behave interdependently of one another.  For example, when a word, such as “book” is shown to the left eye of a test subject with a severed corpus callosum, they don’t see anything at all because words and language are the province of the left hemisphere of the brain.

Sperry’s experiments captured the public imagination and for a time, especially during the “consciousness expanding” era of the late ’60s and early ’70s, the right brain was seen as the “holy grail” of intuition and expanded awareness. The diagram below shows some of the attributes of the left and right brains as they seen then.

Not all researchers saw it quite that way, though, and for nearly two decades, split brain theory was left to academic researchers such as Michael Gazzaniga, who worked under Sperry as an undergraduate and later expanded on his work. Then, in December of 1996, Harvard trained neuroanatomist Jill Bolte Taylor was given the “opportunity” to study her own right brain in action when a blood vessel in her left brain exploded and over the course of 4 hours, virtually destroyed that entire hemisphere. She became, as she said after her recovery, “an infant in a woman’s body.” Even more extraordinary, though, was her spiritual transformation. A trained scientist with no interest in metaphysics, she discovered that:

I am an energy being connected to the energy all around me through the consciousness of my right hemisphere. We are energy beings connected to one another through the consciousness of our right hemispheres as one human family. And right here, right now, all we are brothers and sisters on this planet, here to make the world a better place. And in this moment we are perfect. We are whole. And we are beautiful.

The quote above is from Jill Bolte Taylor’s TED talk in 2008.

Taylor’s road to recovery is as remarkable as her experience of  left brain death. Needless to say, she had no personal desire to return to her old way of perceiving the world, but wanted to share her revelation with the world. After a blood clot the size of a golf ball was removed from the left side of her brain, she began an eight year journey back into the little “I am” of her ego.

Jill Bolte Taylor and others argue that our Western conditioning leads us to lean towards the limited vision of the left brain. At the same time, they see its value for survival and communication. The key, they say, is to restore balance between the hemispheres and see both the big picture and be able to make a positive contribution to the world.

As is true with most theories, the split brain theory is controversial and Taylor has her detractors. Nevertheless, it’s hard to argue with her more important message: “The more time we spend choosing to run the deep inner peace circuitry of our right hemispheres, the more peace we will project into the world and the more peaceful our planet will be. And I thought that was an idea worth spreading.”