Brain hemisphericity

Beyond the world of learning styles, there are some popular beliefs that are downright misconceptions. We have heard the New Age myth that we only use 10% of our brains, which has no basis at all in neuroscience or psychology, but is often repeated by motivational speakers and authors of self-help books – speakers and writers with no research credentials or background in psychology or cognitive science. Even more pervasive is the right/left brain myth, which is even heard in educational circles. This popular belief has no basis in cognitive science.

First, these are two hemispheres of the same brain, not a “left brain” and “right brain.” There are some differences in functions of the left and right hemispheres of the brain, but it is not at all like the popular “left/right brain” urban legend; the reality is much more complicated. There is no evidence that the left hemisphere is predominantly analytical or that the right hemisphere is predominantly holistic and intuitive. Nor is it true that language, math, music, and other abilities are localized to just the left or right hemispheres. Rather, they are distributed throughout the entire brain. We think of music as “right brained” but both hemispheres are involved. For example, part of the left hemisphere processes musical sequences (tones, notes), while the right hemisphere processes affective aspects of music. We think of math and geometry as “left brained” but various aspects of math and geometry are divided between both hemispheres.

For a majority of the population, the grammatical functions of language are largely localized in the left hemisphere. But for some people, these functions are allocated to the right hemisphere, or are distributed among both hemispheres (no one knows why this is so). Language, however, consists of much more than grammar. Other important components of language are the lexicon (vocabulary) and semantics (word meanings, and in connection with that, our knowledge of the world) – these kinds of information are spread throughout the brain. Some aspects of language are localized to the right hemisphere, such as the interpretation of pragmatic information (various types of contextual and non-grammatical information), and possibly, some aspects of grammar.

There is no evidence for a strict dichotomy between left-brained and right-brained people. Some people can be strong in both verbal and musical skills (supposedly left and right brained skills); others can be strong in verbal skills but weak in math skills (both supposedly left brain skills). Nor is there evidence that each hemisphere works in a fundamentally different way (analytical versus holistic information processing, for example), as various skills like language, math and music are spread across both hemispheres. Each of these intellectual domains is a complicated set of neural networks. Language, for example, can be thought of as a large super-network, consisting of smaller networks for syntax, phonology, semantics, pragmatics, and others, and each of these in turn being composed of smaller sub-networks. Whether such modules are more analytical or holistic in terms of how information is processed has more to do with how these modules are configured (e.g., how many neurons), how they are connected to other modules, and the kinds of information that they deal with, not their location in a specific hemisphere of the brain. Thus, the pop psychology “left / right brain” characterizations that one hears of in the media and popular sources are a gross distortion of real psychology, and have no basis in cognitive science.

One other neurological myth that is occasionally heard has to do with the corpus callosum, a bunch of neurons between the left and right hemispheres that allow for cross-talk between the hemispheres. It has been reported that women have more connections in this area, i.e., have a larger corpus callosum, and as a result, are better at communication skills and multi-tasking. This was based on an older study that was not well done, and was later discredited by other studies. Women may have better skills in those areas, but it is not due to a larger corpus callosum, and one must keep in mind that humans in general are not good at multi-tasking as we think we are. For example, various studies have shown that driving while engaged in other activities that require one’s attention, such as talking on a cell phone, cause distraction, leading to more car accidents (driving and talking even with hands-free cell phones or speaker phones are just as dangerous). While women are generally better drivers, they too cannot multi-task well between driving and talking on a cell phone.

1 See also

For more on pop psychology myths, one may refer to the well written and readable book by Lilienfeld et al. (2010).

• Lilienfeld, S. O., Jynn, S. J. Ruscio, J., & Beyerstein, B. L. (2010). 50 Great Myths of Popular Psychology. West Sussex, UK: Wiley Blackwell.