In the 1970’s, a neuropsychologist named Roger Sperry, together with his student Michael Gazzaniga, began testing patients to find out what aspects of the human mind are processed in each hemisphere of the brain. This pioneering work ultimately won Sperry the Nobel Prize in 1981, and Michael Gazzaniga went on to become the father of cognitive neuroscience. But it also seeded the now popular “right brain vs. left brain” myth.
Early Medical Procedures
In the 1960s, neurosurgeons performed surgeries that severed the routes through which abnormal neuronal activity can transfer from one side of the brain to the other, along with the corpus callosum. The neurosurgeons called these new operations commissurotomies, and they found that these procedures successfully curbed the spread of seizures in a number of severely epileptic patients. Their success came from being able to fully sever the communication between the two halves of the brain.
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We don’t do this surgery very often anymore because the drugs available for curbing epilepsy are much better than they were in the ’60s, and less invasive surgical procedures have also been developed. Around this time, a neuropsychologist named Roger Sperry, together with his student Michael Gazzaniga, began testing these so-called split-brain patients to find out what aspects of the human mind are processed in each hemisphere of the brain. This pioneering work ultimately won Sperry the Nobel Prize in 1981, and Michael Gazzaniga went on to become the father of cognitive neuroscience. But it also seeded the left-logical, right-creative brain myth.
How to Talk to One Half a Brain
Once neurosurgeons began performing commissurotomies, they started producing patients with left and right hemispheres that could no longer exchange information, so this means that what their left brain knows, their right brain might not, and vice versa. Realizing this was the case, Sperry, Gazzaniga, and other investigators began devising novel ways to query one-half of the brain at a time.
For example, using the fact that what is in our left visual field is only seen by the right hemisphere, they would show the right hemisphere a series of images very briefly, and then they would ask the patient to respond in some way. The tricky thing about these split-brain patients is that they compensate for the fact that their two hemispheres operate independently by moving their heads so that anything they see or hear enters both sides of the brain. If you met one, you’d hardly notice that anything is amiss.
So, in order to talk to one hemisphere without the other interfering, the psychologists studying the patients had to devise a clever apparatus that limits the information that each hemisphere receives.
They could, for example, have the patient looking straight ahead, and then flash a word to the left or the right and thereby control which hemisphere sees the word. Or they can put up a screen so that the patient can’t see her hands, and then present a set of objects to one hand or the other. With this apparatus, the psychologists could then get information from one or the other hemisphere.
Every time you talk with someone, you’re relying on the left hemisphere of your brain to keep up with and make sense of the exchange. So when the split-brain patients were asked what they saw with their right hemisphere, often they would simply say “I don’t know” or “Nothing,” since the talkative left hemisphere didn’t have access to what the right hemisphere was seeing.
But then, if they were asked to choose from a set of alternatives, say by pointing to a picture of something that’s associated with the thing that their right brain saw, or to pick up an object that matches the word with their left hand, they themselves would be completely surprised when their own left hand instinctively reached out and made a choice or responded to a command. In fact, they often felt as though they were just guessing.
So, for instance, when the command “rub” was presented to the right hemisphere, the patient began to rub his head with his left hand. Or when the word “walk” was shown, the patient would push her chair away from the testing table and begin to get up. And here’s what’s really fascinating. When the patient was asked why he or she performed that particular action, the left brain, which dominates speech, spontaneously made up a story to explain the behavior.
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So the patient who rubbed his head was asked what command his right brain had been shown, and he responded by saying itch. But remember, the command was “rub”—but itch makes sense. And when the woman who began to get up from the table was asked why she was leaving, she responded by saying, “Oh, I need to get a drink.” She didn’t realize that her right hemisphere had seen the command to walk.
Introducing “The Interpreter”
Michael Gazzaniga was the first to suggest that in between these patients’ actions and their responses, there’s a part of their brains that interprets what they’re doing. He called this storytelling function of the brain the interpreter, and he localized it to the left hemisphere along with language.
Another term for this type of interpretation, this justification of an action without enough information to know for sure why it was done, is confabulation. The American Psychiatric Association’s official Diagnostic and Statistical Manual of Mental Disorders defines confabulation as the recitation of imaginary events to fill in gaps of memory, or, in the case of the left hemisphere in split-brain patients, gaps in knowledge. As my former mentor at the University of Toronto, Morris Moscovitch, describes it, confabulation can be thought of as honest lying.
Now, Gazzaniga found that confabulation in split-brain patients occurred when the left-sided interpreter was forced to justify an action without information from the right hemisphere of the brain for why it happened. This means that when the left brain didn’t know what the right brain was doing, it simply made up a story after the fact in order to explain the decision.
And it was a story that the patient really believed to be true. These instances of confabulation in patients with commissurotomies give us pretty fascinating insights into how our own intact brains function. And by querying one hemisphere or the other independently, these patients have provided us with lots of information about what types of cognitive processes and information are localized in each of the two hemispheres in most people.
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Our Working Brains
But the most striking thing about split-brain patients is that it’s really hard to tell, from interacting with them, that there’s anything amiss at all. The truth is that both sides of the brain spend far more time working together and sharing information than operating independently in the healthy brain. And even in the split-brain, the patient can compensate by moving their heads, for example, to ensure that both sides get the information they need to function.
The experiments that demonstrate independent actions of the two hemispheres in the split-brain patients have to be carefully crafted and controlled, because most of the time the patient will compensate for the cuts and just get the information each hemisphere needs by turning his or her head or making some other small behavioral adjustment.
Even just by looking at the brain’s connectome—the wiring diagram that illustrates the connections between different parts—it’s abundantly clear that the two sides of the brain are intimately connected. That’s why the left-right logical-creative argument is largely a myth: they work together and are both necessary for complex thought.
Busting the Modular Myth
When we try to map the lateralization of functions—that is, when we design experiments to find differences between the left and right sides of the brain—we quickly realize how difficult this can be. The idea that the brain is strictly modular, that different brain regions have different functions, is no longer accepted in neuroscience.
Instead, we talk about networks of circuits or regions that work together, and many of the circuits cross the line between the two hemispheres. What’s more, patients who have had half of their brains surgically removed demonstrate just how malleable lateralization can be. Removing half a brain is called a hemispherectomy, and it’s a last resort treatment for patients with a damaged hemisphere that is threatening or harming the rest of the brain.
This situation can happen, for example, if a person has a malformed hemisphere that’s taking up too much space and not functioning properly, like a child whose left hemisphere grew much faster than the right and is now pushing up against the skull and impairing the growth of the rest of the brain.
Needless to say, hemispherectomies are rare. They’re usually performed on children whose brains have a better chance of recovering function than those of adults, and it’s well established that lateralized functions in the healthy brain, like language, can be rewired into the other hemisphere, especially if the patient is very young.
This rewiring demonstrates one of the amazing super powers of the brain, the ability to repurpose cortical real estate for important functions when the regions that are supposed to carry them out are damaged.
This plasticity is seen both before a child develops the activity—for example, one born with just one hemisphere—and even after the function has begun to develop, as is the case in children who can already speak but then undergo a hemispherectomy of the left side. The remarkable thing about these patients is that they can go on to lead impressively normal lives.
So whether we’re talking about split-brain patients or children who have had a hemispherectomy, we see a reality that is very complex. We can’t just say the left hemisphere controls analytical functions and the right hemisphere controls the creative process—it’s just not that simple.
I’m an opera singer as well as a cognitive neuroscientist, And when I’m back in the studio, I’ve been told to enhance my creativity by engaging in warm-up exercises that tap into right brain functions, like movements involving the left side of the body, or writing a sentence with the left hand, or some similar activity. It’s really hard for me not to cringe in these moments, because the myth is so deeply ingrained and yet so utterly wrong.
It’s possible that some of these tools can enhance creativity, but that’s because they take you out of your comfort zone, or overturn stereotypic behaviors, or get your mind out of a rut—it’s not because they’re awakening your dormant right hemisphere. Your right hemisphere is chugging right along and exchanging messages with your left side all the time. And studies linking creativity to brain wiring have given us mixed results. Depending on how you measure and define it, some studies show that greater connectivity between the hemispheres enhances creativity, while others show the opposite.
The interpreter that we talked about a few moments ago is active in all of us. It explains our behavior by constructing stories from events we experience. It’s our inner voice or monologue, and it helps us understand our own choices and ourselves. For split-brain patients, the interpreter chooses to confabulate a meaning instead of admitting that it doesn’t have one. And research suggests that all of us might be prone to confabulating, and we won’t even know we’re doing it. None of us is immune, particularly when it comes to justifying the many instinctual or intuitive decisions that we’re forced to make every day.
Engaging my left arm in an acting exercise doesn’t mean that my right hemisphere is now dominating all the other processes that my brain is working on. It might help me become less inhibited and have other psychological effects, but it’s not going to suddenly make me pay more attention to prosody, for example, just because I’m engaging my right motor cortex.
The Collaboration Theory
Just as Michael Gazzaniga’s interpreter theory suggests, a part of our brain observes our behavior and constructs a plausible story that we then sell to ourselves as the truth. We relay that story to others, sometimes in surprisingly elaborate detail. And so, ironically, if this interpreter is primarily located in the left hemisphere, it just might be that much of our creativity comes from the construction of these left-sided stories.
So the bottom line is that the two hemispheres might divvy up some aspects of the workload, but they cooperate and collaborate much more than they compete. And while they each might have their strengths, most functions are dually represented in both sides. And, finally, there’s no evidence to support the notion that the left hemisphere is not intimately involved in the creative process. In fact, for many of us, it just might be driving the bus.