Lateralization of brain hemispheres

By: Bella Dalba

            On occasion, theories that develop within the confines of the scientific community emerge out of the proverbial darkness, and are subsequently incorporated into popular culture. The idea of black holes or quantum leaps plays a metaphorical role that is only loosely tethered to their original scientific meanings. In psychology, the theory that some people are more “right-brained” while others are more “left-brained” is based on the lateralization of brain function.

This misconception is employed as the foundation for a myriad of personality assessment tests, self-motivation books, and team-building exercises. Popular culture would have you believe that logical, methodical and analytical people are left-brain dominant, while the creative, subjective, and artistic types are distinctly right-brained. Like many popular psychology myths, this too grew out of observations about the human brain that were dramatically distorted and exaggerated.

The roots of the left/right story lie in a small series of operations in the 1960s and 1970s. Roger W. Sperry, a Nobel-laureate neuroscientist at the California Institute of Technology, and a team of associate doctors sought a treatment for severe epilepsy. Sixteen patients suffering from this affliction agreed to undergo surgery in which the corpus callosum, the main nerve bundle that joins the two halves of the brain, would be severed. Once released from the hospital, Sperry and his team began observing their cognitive functioning. Many of the split-brain patients found themselves unable to name objects that were processed by the right side of the brain, but were able to name objects that were processed by the left. Based on this information, Sperry hypothesized that language was controlled by the left side of the brain, setting the precedent for a “definitive” correlation between ability and a specific brain lobe.

As previously stated, laboratory findings do not always make their way into popular culture, and this supposedly groundbreaking psychoanalysis provided an unfortunate opportunity for misinterpretation of what was, in essence, a limited set of experiments. In 1973, the New York Times Magazine published an article titled, “We Are Left-Brained or Right-Brained,” which began: “Two very different persons inhabit our heads...One of them is verbal, analytic, dominant. The other is artistic.” TIME featured the left/right story two years later. Harvard Business Review and Psychology Today followed soon thereafter. Never mind that Sperry himself cautioned that “experimentally observed polarity in right-left cognitive style is an idea in general with which it is very easy to run wild.”

Later research has shown that the brain is not nearly as dichotomous as once thought. For example, recently published findings indicated that abilities in subjects such as math are actually strongest when both halves of the brain work together. Today, neuroscientists know that the two sides of the brain work together to perform a wide variety of tasks and that the two hemispheres communicate through the corpus callosum.

"No matter how lateralized the brain can get, the two sides still work together," science writer Carl Zimmer explained in an article for Discover magazine. "The pop psychology notion of a left brain and a right brain doesn’t capture their intimate working relationship. The left hemisphere specializes in picking out the sounds that form words and working out the syntax of the words, for example, but it does not have a monopoly on language processing. The right hemisphere is actually more sensitive to the emotional features of language, tuning in to the slow rhythms of speech that carry intonation and stress."

In one study by researchers at the University of Utah, more 1,000 participants had their brains analyzed in order to determine if they preferred using one side over the other. The study revealed that, while activity was sometimes higher in certain important regions, both sides of the brain were essentially equal in their activity on average.

Needless to say, the left-right perception has been completely discredited. However, a new theory evolved from the chaotic misinterpretations: the potential division between top and bottom sections. This frequently overlooked anatomical division of the brain is slowly becoming recognized. Depending on the extent to which a person uses the top and bottom parts, four possible cognitive modes emerge. These modes reflect the amount that a person likes to devise complex and detailed plans and likes to understand events in depth. Separately, the top synthesizes plans and thoroughly revises them when/if expected events do not occur, while the bottom classifies and interprets what is perceived.

Based on decades of research, the theory holds that this distinction can help explain why individuals vary in their thought and behavior patterns. Interaction between each particular section is the key to solving the differentiations, not merely studying their individual functions. This contemporary approach avoids the pitfalls of the left brain/right brain theory, as the characterizations are based in cataloged research, and it is emphasized that the two sections work in conjunction with each other -- it is the relative balance of how much reliance is placed on the one of the two sections that determines each cognitive mode.

Despite the solidarity of the research, this notion still remains a theory: however, if there is one indisputable fact, it is that we, as a species, are continually inclined to try to understand whatever matter we encounter, even something as complex as the brain.