Book T of C
Chap T of C
Several different theorists—starting with Kinsbourne in the 1970s—suggested the two hemispheres might act as a "push/pull" control system, similar to an accelerator and a brake, with the left hemisphere (mostly in the prefrontal area behind the eyes) contributing to approach tendencies and the right hemisphere (mostly in the area of the amygdala) contributing to avoidance tendencies.
How is the brain like a "control system" for approach and avoidance?
What can most people demonstrate to themselves in the mirror?
In most people, the right hemisphere is more expressive of emotion. Consequently, most people are more expressive on the left side of the, controlled by the right half of the brain. People usually sneer or wink on the left rather than the right. If you hold a piece of cardboard over half your face and look in the mirror, you might find that the right half of your face looks relatively expressionless compared to the left. When you experiment with happy and sad expressions, the left half of your face will show more emotion, if you are typical.
Can normal people learn to activate one or another hemisphere, so that the entire hemisphere is more dominant than the other one, in mental activity? This comes dangerously close to "pop psychology." In the best-selling book Drawing on the Right Side of the Brain (1993) a California art teacher named Betty Edwards claimed to be able to train people to use their right hemispheres to produce art by forcing right-handed people to use their left hands while making sketches. The book produced a small industry of workshops based on the idea, which was widely and uncritically accepted. To me, it is a fine example of a "fun idea" and therefore quite likely to be untrue or, at best, oversimplified and misleading.
In the case of the woman who could "switch on" either hemisphere, what skills were associated with activity of each side?
However, there are some well-documented cases of people who are able to control levels of hemispheric activity. Gott, Hughes and Whipple (1984), writing in the scholarly journal Neuropsychologia, described a normal woman with intact hemispheric connections who could "turn on" one hemisphere or the other at will. They provided evidence from biological and behavioral tests to show that when she "made her switch" the focus of her brain activity went from one hemisphere to the other.
The subject was a 31-year-old right-handed female. From an early age she noticed two distinct patterns of mood and activity in herself. At the age of 16 she learned to control the states so she could switch them voluntarily. The woman called one of the states "me" and the other "it." Left hemisphere activity correlated with "me." "Me" was used for logical discussions, planning, writing, arithmetic, playing Scrabble, reading for information, or confronting new people and situations. The patient called this her "business woman" side.
The other state, called "it," was correlated with right hemisphere activity. The woman referred to this as her "gardening" personality. During this state she was more likely to be relaxed, comfortable, or in sexual moods. When "it" was dominant she improved her ability at drawing, sports, and playing music. She improved at spatial tasks such as map reading and felt more at ease socializing with friends. The researchers verified the performance differences with laboratory tests.
Which ideas about right-brain and left-brain activity are well-supported by research evidence, and which are not?
The foregoing case history was documented with precise brain measurement techniques. However, many of the commonly accepted ideas about right- brain and left-brain differences are pop psychology, not well-documented science. The best-supported distinctions about right and left hemisphere specialization have already been mentioned. About 95% of right-handed people have language in the left hemisphere. It is also true that the right hemisphere contributes more to emotional expression and spatial processing (such as reading maps). That's about it! Most of the other speculations that appear in popular sources (for example, that the right brain is "artistic" or holistic while the left brain is "analytic" or drab and ordinary) are not supported by precise, replicated experiments.
As long ago as 1978 the topic of hemispheric specialization was being denounced as "fad of the year" (Goleman, 1978). Michael Corballis of the University of Auckland wrote an article titled "Laterality and myth" in 1980. Ten years later he was reviewing a book titled "The rise and fall of hemispheric specialization." Corballis lamented the fact that the idea of hemispheric specialization was still widely accepted (Corballis, 1990). He did not like the book, incidentally. He wrote "the best thing about it is the title."
I wrote Corballis in 1998 to see if he had changed his views:
Dear Dr. Corballis:
I enjoyed your article "Laterality and Myth" in 1980 plus your review of "The rise and fall of hemispheric specialization" in 1990, in which you lamented the fact that the idea of hemispheric specialization was still widely accepted. (You wrote, "The best thing about it is the title.") Are you on a ten-year cycle, planning another review for 2000?
On a more serious note, do you have a sentence or two I can share with my introductory psychology students regarding your current views of lateralization? One still sees the old mid-70s-ish "right brain/left brain" stuff in ads and pop psychology sources. I am curious about whether your thinking has changed, given the flood of brain scanning data in the 1990s, and if you have established a different position regarding the issue.
When students ask me about it, I usually say that left hemisphere specialization for language is well established, particularly in right-handed people with no left-handed relatives, and that right-hemisphere superiority in emotional expression and spatial processing can be supported by replicable experiments and neuropsychology data, but beyond that much is exaggerated. I would value any corrections if you think I am misleading my students. [Personal communication, July 21, 1998]
Dr. Corballis responded, in part:
How did Dr. Corballis summarize the well-documented differences in hemispheric specialization?
Your message makes me realize, with horror, that I do seem to be on a ten-year cycle! I entirely agree with your assessment: language is in the left hemisphere, dammit, and emotional and spatial skills do seem to have a right-hemispheric bias.
Dr. Corballis also sent a pre-publication draft of a chapter (indeed scheduled for publication in 2000 as part of his ten year cycle) in which he detailed the mythology about lateralization. He noted that claims about superiority of the right or left brain for various types of mental processing go back to the mid-1800s and are continually changing. In his summary he wrote:
...The supposed creative, intuitive skills of the right hemisphere are far from proven and are based more on speculation and the power of myth than on any incontrovertible scientific evidence.
Maybe the problem with hemispheric specialization is not that it is a complete lie but that it tends to be exaggerated, overemphasized, and simplified...all at once. That irritates professionals like Corballis who are constantly seeing references to "right and left brain thinking" in the media.
What "nonsense" about the right hemisphere is widely circulated on the web?
Students can perform an internet search for "right hemisphere thinking" and they will see hundreds of web sites devoted to this topic. When I looked, every one of them was completely gullible about the idea of right-hemisphere thinking. Many were attempting to make money by offering training courses designed to encourage right-brained thinking. I literally could not find a single web site that offered a skeptical or cautious viewpoint on this topic! But now you know better. It is nonsense according to real experts in the field.
What does the author predict for the future, as brain scanning improves?
Talk of hemispheric specialization is not going away any time soon. Tools for locating centers of brain activity are increasingly powerful. Brain scanning techniques like functional MRI are capable of pinpointing tiny islands of activity in the brain. Inevitably, many psychological functions will be found to involve one hemisphere more than the other. Trained musicians are said to use the left hemisphere relatively more for judgment of relative pitch, for example. Object recognition is said to be better on the right. Guided visual search is better on the left, and so forth. Eventually there will be a catalog of thousands of skills that are better on the left or the right, or the front or the back, or in one lobe or another.
What is the apparent truth about specialized areas in the brain?
One might conclude that there is some truth to the idea of superior skills in the right or left hemisphere, but this is a far cry from "right brain/left brain thinking." We might speak just as logically of "front vs. back" thinking, because some tasks will be performed well in the frontal lobes, others in the occipital lobe at the back of the brain. How about "mid-brain thinking" for tasks performed well by the parietal lobe?
The truth is that the brain is full of specialized areas that are activated by particular tasks. In normal thinking, including intuition and artistic activity, areas from various locations in the brain are activated at the same time, and they work together.
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Copyright © 2007 Russ Dewey