Conventional wisdom has it that some people are right-brained, meaning they tend to be creative, intuitive, and emotional, while others are left-brained, meaning they tend to be logical, analytical, and methodical. But once again conventional wisdom has vastly oversimplified and overstated the situation. (There’s a reason why conventional wisdom tends to function this way, but that’s another blog post.)
It’s true that the two hemispheres of the brain function differently. Much of what we know about the differences between the two hemispheres is the result of research conducted in the 1960s on patients with split brains. Normally the two hemispheres are in ongoing communication with each other via the bridge of fibers called the corpus callosum. But the corpus callosum was surgically severed in some epilepsy patients in a last-ditch attempt to relieve their symptoms.
Michael Gazzaniga, Roger Sperry, and two other researchers conducted the testing on these individuals that revealed some of the effects—many of them quite surprising—of cutting off communication between the hemispheres. Later on, Gazzaniga conducted additional research with Joseph LeDoux.
To me, the most interesting thing they discovered is what happens as a result of visual information no longer being passed from one hemisphere to another. Language is primarily a function of the left hemisphere. So although the right hemisphere could recognize an image not shown to the left hemisphere, it couldn’t communicate about it verbally. David Eagleman summarizes these experiments in his book Incognito. Remember that brain wiring is contralateral, which means that the right hemisphere processes information from the left visual field and controls the movements of the left hand—and vice versa for the left hemisphere.
In 1978, researchers Michael Gazzaniga and Joseph LeDoux flashed a picture of a chicken claw to the left hemisphere of a split-brain patient and a picture of a snowy winter scene to his right hemisphere. The patient was then asked to point at cards that represented what he had just seen. His right hand pointed to a card with a chicken, and his left hand pointed to a card with a snow shovel.
The experimenters asked him why he was pointing to the shovel. Recall that his left hemisphere (the one with the capacity for language), had information only about a chicken, and nothing else. But the left hemisphere, without missing a beat, fabricated a story: “Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.”
When one part of the brain makes a choice, other parts can quickly invent a story to explain why. If you show the command “Walk” to the right hemisphere (the one without language), the patient will get up and start walking. If you stop him and ask why he’s leaving, his left hemisphere, cooking up an answer, will say something like “I was going to get a drink of water.”
The chicken/shovel experiment led Gazzaniga and LeDoux to conclude that the left hemisphere acts as an “interpreter,” watching the actions and behaviors of the body and assigning a coherent narrative to these events. And the left hemisphere works this way even in normal, intact brains.
One important thing to remember is that for people with intact brains, the two hemispheres remain in constant communication with each other. We are whole-brained people who use both parts of our brain all the time, including during the creative process and in the course of logical problem-solving.
Although this, too, is an oversimplification, it’s closer to the mark to say that if we did not have language or discernment, our creative ideas would be useless and possibly incoherent. And if we did not have emotion and imagination, we would have no context for decision making.
Not only is neither hemisphere “better” than the other, you may be surprised at the conclusion Gazzaniga has reached about which hemisphere is more “conscious” and which hemisphere is more literal.
After many years of fascinating research on the split brain, it appears that the inventing and interpreting left hemisphere has a conscious experience very different from that of the truthful, literal right brain. Although both hemispheres can be viewed as conscious, the left brain’s consciousness far surpasses that of the right. Which raises another set of questions that should keep us busy for the next 30 years or so.
I’m looking forward to the results of that additional research!
Both of my hemispheres are spinning, but my poor body doesn’t know which way it should spin!