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Left vs. Right: What Your Brain Hemispheres Are Really Up To

Right brain left brain

In the 1980’s, brain researchers viewed the two sides of the brain as dichotomously opposed: the right hemisphere was seen as a gestalt processor, good at “seeing the big picture,” while the left hemisphere was attributed with detail processing skills. Other views at that time attributed the left hemisphere with being more logical and analytical while the right hemisphere was considered more intuitive.[i]

Some went so far as asserting that men and women exhibited different right vs. left preferences: men were attributed with stronger left hemisphere skills and women better right hemisphere skills. Although this male-female distinction was never empirically verified through research, the somewhat “pop-psychology” view that the right hemisphere is important for skills like music and art, predominated. In fact, there were books written instructing individuals on how to “draw with the right hemisphere” or how to “teach to the right hemisphere”.[ii]

It now appears that some of these notions need to be revised.  A current view is that, for the majority of us, the right hemisphere is a pattern recognizer that may develop before the left. From this perspective, the right hemisphere enables a child to attend to and appreciate the gist of a sensory experience within each cognitive domain. For example, in acquisition of mathematical concepts, the right hemisphere may enable a young child to appreciate quantities in terms of more vs. less prior to assigning numerical values to the quantities (which would involve left hemisphere skills). There is research demonstrating that babies can discern a group of dots in terms of general aspects of quantity.[iii]

Patricia Kuhl at University of Washington in Seattle has shown that typically developing infants show an interest in human voices over other environmental sounds like a car horn or doorbell, and direct their attention to human voice when it conveys information that is interesting.[iv] Ultimately this may lead to an understanding of how the melody of a voice is used to convey a person’s intent.  In other words, recent research suggests that the right hemisphere may be best at processing patterns like voice contour, facial expression, aspects of size and quantity, gestalt aspects of the world which, from a developmental perspective, represent the way children begin to learn about cognitive areas like music, art, mathematics or language.

Considering the cognitive domain of music, for example, the right hemisphere appears to have a fundamental preference for recognizing melody, which allows a young infant to be interested in and ultimately reproduce early nursery songs. In the realm of visual processing, the right hemisphere has been shown to be better at perceiving the form or outline of an object than the details contained within the object.[v]. And, similarly, although many people regard the left hemisphere as dominant for language, newer research has shown that the right hemisphere is superior at processing information like vocal inflection (prosody), and perhaps going directly from word to meaning, especially in very familiar phrases like idiomatic expressions (eg., “it is raining cats and dogs”) while the left hemisphere is more important for processing aspects of language that depend on analyzing the specific sequence of the sounds and words which are essential for understanding grammatical form of language and perceiving internal details of words.[vi]

Several neuroscientists have accordingly revised and expanded the early right-left dichotomy to see the right hemisphere as preferential in processing form, structure, and perhaps, direct links to emotion,[vii]  while the left hemisphere handles complex, rapidly changing stimuli, in which discerning the specific sequential order is critical to perception (as in speech perception, for example, where one must discern and order very rapidly changing complex acoustic events very quickly.)[viii]

Another revision to the older view of right versus left hemisphere complements the view that the right hemisphere is preferential for pattern analysis, and comes from developmental neuroscience which has reported research that supports the contention that for most cognitive skills the right hemisphere matures before the left.[ix] This certainly seems to the case when one looks at the early stages of neuronal development and migration in the fetal brain,[x] and also the building of early axonal superhighways, as well as the research on myelination.[xi] In fact, it may be that when this typical right to left maturation does not occur, developmental neurological abnormalities result. For example, there is some early research evidence that Autism Spectrum Disorders may represent one example of developmental deviations in this typical right-to-left developmental hierarchy.[xii]

Although it may seem somewhat of a stretch from the early research in this area, one can observe how this organization might be reflected in early childhood development in the stages children pass through in the gradual mastery of skills. For example, when a child first begins to enjoy music, the observant adult notices that the child moves his or her whole body to the musical rhythm. For nursery songs, like “Twinkle Twinkle Little Star” the child often begins by humming the melodies. In both cases, this may represent right hemisphere processing.

In most cases, it will be a few years before the child will be able to read musical symbols which would presumably involve more left hemisphere skill. We do have research that shows that when three month old babies are first listening to oral language, the right hemisphere is much more active than the left.[xiii] Patricia Kuhl has shown that mothers instinctively seem to match their speech to babies’ early developing perceptual preferences by exaggerating melodic inflection with young babies, probably reflecting their intuitive knowledge that they need to exaggerate the language cues (intonational contour and vocal inflection) that the right hemisphere seems to process preferentially while deemphasizing the production of the speech sounds themselves (left hemisphere preferences).[xiv]
 

[i] Deutsch, Georg and Sally P. Springer. Left Brain, Right Brain: Perspectives From Cognitive Neuroscience . W.H. Feeman and Company/Worth Publishers. 2001.
[ii] Edwards, Betty. Drawing on the Right Side of the Brain. Penguin Putnam Press. 1999.
[iii] Xu, Fei et al. (2005) Number sense in human infants. Developmental Science. Vol. 8. 2005.
[iv] Kuhl, Patricia. Early Language Acquisition: Cracking the Speech Code. Nature Reviews Neuroscience. Vol 5. 2005.
[v] Devinsky, Orrin and Mark D’Esposito. Neurology of Cognitive and Behavioral Disorders. Oxford University Press. 2004.
[vi] Hickok, Gregory and David Poeppel. The Cortical Organization of Speech Processing. Nature Reviews Neuroscience. 2007.
[vii]Cahill, L. et al. Sex-Related Hemispheric Lateralization of Amygdala Function in Emotionally Influenced Memory: An fMRI Investigation. Learning and Memory. Vol. 11: 261-266. 2004
[viii] Tallal, Paula. Improving Language and Liteacy is a Matter of Time. Nature Reviews Neuroscience Vol. 5. 2004.
[ix] Huttenlocher, Peter. Morphometric Study of Human Cerebral Cortex Development. Neuropsychologia. Vol. 28. 1990.
[x] Galaburda, Albert et al. From Genes to Behavior in Developmental Dyslexia. Nature Neuroscience  Vol 9. 2006.
[xi] Herbert, Martha et al. Brain Asymmetries in Autism and Developmental Language Disorder: A Nested Whole-Brain Analysis. Brain: A Journal of Neurology.2004.
[xii] Herbert, Martha et al. Ibid.
[xiii] Hickock, Gregory and David Poeppel. Ibid.
[xiv] Kuhl, Patricia. Ibid.

Related Reading:

A Gymnast, a Cursor and a Monkey Named Aurora

7 Amazing Discoveries from Brain Research

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