In his keynote address at the 2004 Democratic National Convention, then-Illinois State Senator Barack Obama declared that “there is not a liberal America and a conservative America; there is the United States of America.” Obama argued that the liberal-conservative dichotomy is a Procrustean bed: an erroneous belief that the political differences between Americans overwhelm the similarities that unite them.
The myth that people are either right- or left-brained is a similar Procrustean bed because it espouses a simplistic dichotomy that distorts a more complicated reality. Psychology and neuroscience have shown repeatedly that there is not a right brain and a left brain; there are the united hemispheres of the brain. Those who would have you believe otherwise are misinformed, neuroprofiteers (more on them in a future post), or both.
The myth holds that there are two types of people in the world. One type includes people who look like engineer stereotypes: they think analytically, prefer careful, deliberate planning, and take a reasoned, logical approach to life. The other type includes people who look like poet stereotypes: they think creatively, act spontaneously, and have a carefree, open-minded perspective about things.
Unfortunately for this typology, decades of scientific research on human personality paint a different picture: personality is comprised of five dimensions (John, Naumann, & Soto, 2008). Unlike the myth, these dimensions, called The Big Five, do not suggest a dichotomous typology. This research suggests that there are plenty of analytical thinkers who act spontaneously; traits like these are not anti-correlated.
But the myth goes even further. It states not only that there are two types of people in the world, but also that this typology is caused by differences in brain function. According to the myth, analytical people rely more on the left hemisphere of their brain whereas creative people make greater use of the right hemisphere of their brain.
This hypothesis supposes that the left and right hemispheres serve different functions or operate on information in dissimilar ways. Though some hemispheric differences in brain function and information processing exist (Toga & Thompson, 2003), the existing evidence does not support the drastic personality dichotomy suggested by the myth (Hines, 1987).
A Joint Effort
The two hemispheres are always working together to allow us to act, think, and feel. For example, each hand is controlled by the motor cortex in the opposite hemisphere (i.e., the right motor cortex works the left hand). Similarly, the somatosensory cortex in each hemisphere processes touch from one hand. To a large extent, brain symmetry reflects body symmetry and supports the use of a bilateral body.
Coordination between the right and left side of the brain is possible because the two hemispheres are united by a thick bundle of neurons called the corpus callosum. These neurons ensure that information flows freely from one side of the brain to the other. The left hemisphere is never incommunicado from the right hemisphere. (However, the corpus callosum can be removed surgically; one such split-brain patient is shown in this video).
Inter-hemispheric collaboration is even necessary to support abilities that are thought to use one hemisphere exclusively. For example, though language is often associated with the left hemisphere, neuroimaging studies show that both hemispheres are likely to be involved in language processing (Vigneau et al., 2006). Even a person who loses the left hemisphere during childhood can acquire good language abilities (Smith & Sugar, 1975).
- People are not right- or left-brained
- Psychology shows that personality is composed of five dimensions that are inconsitent with the typology proposed by the myth
- Neuroscience shows that the brain hemispheres work together, performing similar tasks and sharing information to allow us to act, think, and feel
- Individuals and organizations who evangelize otherwise are misinformed and/or want to profit from people’s misunderstanding of neuroscience
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