Hey, I’m Dave. And I’m Joel.
Let’s talk about brains.
At the fictional Hogwarts school for witchcraft and wizardry in the Harry Potter series, students
are sorted into different houses by a magic hat based on their personalities. Similarly,
in elementary school, a teacher may have declared one side of your brain stronger than the other
based on your personality. If you’re a creative or artistic type, you would have been identified
as right-brained. If you’re an analytical or mathematical type, you would have been
identified as left-brained.
You might have even used this picture of your brain to choose a college or a career. And
while we each have a unique set of talents and abilities, there’s no such thing as
being right-brained or left-brained.
Not in the way your school teacher explained it to you, anyway. And if there were such
a thing, almost all of us would be left brained. The left cerebral hemisphere controls the
right side of the body, and about 90 percent of people prefer to write with their right
hand, indicating left brain motor dominance. Moreover, language skills are left lateralized,
or largely controlled by the left hemisphere, in over 90 percent of people. That includes
78 percent of people who are not right-handed.
Does this mean that the remaining few with language in the right hemisphere are “right-brained?”
More likely, these individuals have, on average, the same skills and talents as the other 90
percent of us “left-brained” folks. The place in the brain where language is localized
just happens to be different.
The left cerebral hemisphere is to the “right brained” poet or novelist as the hamstrings
and quadriceps are to a competitive sprinter. Because the ability to understand and produce
language is focused in the left side of the brain in almost everyone, caricaturing these
creative types as using their right brain more than their left brain is just plain silly.
Similarly, visual-spatial abilities are localized to the right cerebral hemisphere, a skill
that is absolutely critical for “left-brained” talents like science or engineering. The ability
to interpret algebraic equations in terms of geometric curves is the specialty of the
right brain.
So where did this right/left mythology come from? As we mentioned, some skills are indeed
strongly lateralized to one hemisphere of the brain. But much of our obsession with
the brain’s left and right cerebral hemispheres may have started with studies of split brain
patients in the ‘50s. During this time, people who suffered multiple seizures a day
underwent intense surgery to treat their epilepsy.
To calm the electrical storms that ravaged these patients’ brains, the nerve fibers
connecting the left and right hemispheres of the brain were cut. These fibers are collectively
known as the corpus callosum. As a once bright highway of information goes quiet, consciousness
changes in profound ways, and the specialties of each cerebral hemisphere are more easily
disentangled.
Once the corpus callosum is severed on the operating table, the new split brain patient
appears astonishingly normal at first glance. But careful experiments reveal that this person
is really two persons, two streams of consciousness in one body. These experiments, performed
by Nobel laureate Roger Sperry, found clever ways of feeding information to only one side
of the body (and, therefore, only the cerebral hemisphere controlling that side of the body).
In one experiment, the right hemisphere was shown an image of a snow scene while the left
hemisphere was shown a picture of a chicken. The right hemisphere was then instructed to
select an image of an object to match the presented scene. After selecting an appropriate
object—a snow shovel—the split brain patient is asked to justify this selection. Remember,
only the left hemisphere, which saw the chicken, can speak. Because only the left hemisphere
can speak, the patient would give a response such as ‘I can use this to shovel out the
chicken coop.’
So why did the left hemisphere give this answer? Not being able to see the snow scene, the
left hemisphere doesn't know that the shovel was selected to shovel snow. Thus, this separate
stream of consciousness invents a new reason involving the chicken scene that it can see.
The right hemisphere cannot speak, but it can point to words like “yes” or “no”
to answer a question. Neurologist V. S. Ramachandran tells the story of a split brain patient who
is asked whether he believes in God. The right hemisphere pointed to “yes” while the
left hemisphere declared “no.” Each hemisphere, it seems, maintains independent beliefs and
personalities, challenging the notion that we are each an indivisible “self.”
But this does not justify the pop psychology concept of “left-brained” or “right-brained.”
The two hemispheres are different, yet brain imaging technologies like functional magnetic
resonance imaging, or fMRI, suggest that, on average, we use both sides of our brain
equally. We are all “brain-ambidextrous.”
So if there was ever a left-brained and a right-brained person, it would be the two
personalities co-habitating the skull of a split brain patient. For the rest of us, these
labels are as fictional as Harry Potter.
Oh, and that thing about only using ten percent of your brain? You can throw that one in the
garbage, too.