Study Debunks Left-Brain, Right-Brain Theory

Tuesday, August 20, 2013

A new study has found no evidence to support that some people display "right-brained" or "left-brained" personality traits. Jeff Anderson, neuro-radiologist at the University of Utah and lead author of the study that just came out in PLOS ONE, explains the findings and what it changes about our understanding of how we think.

Comments [8]

Lateralized brain regions subserve functions such as language and visuospatial processing. It has been conjectured that individuals may be left-brain dominant or right-brain dominant based on personality and cognitive style, but neuroimaging data has not provided clear evidence whether such phenotypic differences in the strength of left-dominant or right-dominant networks exist. We evaluated whether strongly lateralized connections covaried within the same individuals. Data were analyzed from publicly available resting state scans for 1011 individuals between the ages of 7 and 29. For each subject, functional lateralization was measured for each pair of 7266 regions covering the gray matter at 5-mm resolution as a difference in correlation before and after inverting images across the midsagittal plane. The difference in gray matter density between homotopic coordinates was used as a regressor to reduce the effect of structural asymmetries on functional lateralization. Nine left- and 11 right-lateralized hubs were identified as peaks in the degree map from the graph of significantly lateralized connections. The left-lateralized hubs included regions from the default mode network (medial prefrontal cortex, posterior cingulate cortex, and temporoparietal junction) and language regions (e.g., Broca Area and Wernicke Area), whereas the right-lateralized hubs included regions from the attention control network (e.g., lateral intraparietal sulcus, anterior insula, area MT, and frontal eye fields). Left- and right-lateralized hubs formed two separable networks of mutually lateralized regions. Connections involving only left- or only right-lateralized hubs showed positive correlation across subjects, but only for connections sharing a node. Lateralization of brain connections appears to be a local rather than global property of brain networks, and our data are not consistent with a whole-brain phenotype of greater “left-brained” or greater “right-brained” network strength across individuals. Small increases in lateralization with age were seen, but no differences in gender were observed.

Aug. 20 2013 02:08 PM
Tiffany from New York

I write with my right hand, but paint, draw, cut, and throw pottery primarily left-handed. I've always assumed this was a left-brain, right-brain thing, and made complete sense. But if the brain-side story is nonsense, then why would I have these preferences? As far as I know, I was taught all these things by right-handed people.

Aug. 20 2013 11:46 AM
John A

Clearly, culture has absorbed the old L/R label, and needs an equally easy to follow guide if a replacement is needed via science.

Aug. 20 2013 11:43 AM
Tony from Canarsie

I've long thought this left brain/right brain idea was way too pat and simplistic. I also recall almost that every artist I've known who owned a copy of the bestseller "Drawing From The Right Side of the Brain" also owned several of the con artist Carlo Castaneda's inane tomes.

Aug. 20 2013 11:42 AM
fuva from harlemworld

Ok, but laypeople will never get why the left/right brain theory is mythical if neuroscientists can't EXPLAIN...IN PLAIN ENGLISH...WHY.

Aug. 20 2013 11:39 AM
Michael from Ridgewood

I completely agree with JT and the caller. Enjoying listening to Brian trying to figure out himself what's so interesting about "debunking" bad public understanding of current science. We've known for a long time it,s not that simple. See the RSAnimate video The Dvided Brain!

Aug. 20 2013 11:38 AM
art525 from Park Slope

Of course not having heard this yet I can't really comment on it. Howver being left handed and being an artist I have foound a disproportionate number of artists are left handed. The percentage of the population that is left handed is about 10% but when I was in art school I would always ask in my classes how many were left handed and it was at least 50% on average. ANd things like understanding perspective seem to come naturally to us withoutr training. Keep in mind too that Leonardo da Vinci, Michleangelo, Holbein and possible Rembrandt are said to have been left handed. And speaking of Leonardo, we know that his journals were kept in mirror writing and every time I ask a left hander if they can mirror write they either can. If they aren't familiar with it I will demonstrate and they re able to instantly pick it up and do it. Right handers can't. So there are certainly distinct differences.

Aug. 20 2013 10:06 AM
JT from NJ

Ugh. No "debunking" here, just feeding the vox populi maw with oversimplification.

Firstly, the terminology "personality trait" is a misnomer to describe the variables in these studies. The investigators are attempting to identify lateralized networks underlying distinct behaviors. (Handedness is not a personality trait, for instance.)

The oversimplified and sensationalist notion of "right brain" and "left brain" personality goes back to the mid-late '60s and early '70s when pop culture (similar in flavor to the recent Marina Abramovic PR brain wave stunt in your studio, by the way, among others) co-opted results coming out of Roger Sperry's lab at Cal Tech and later studies performed by generations of his students, in subjects (monkeys and humans) that were not "intact," ie. human commissurotomy patients who had undergone surgical dissection of their anterior/posterior commissures and corpus callosums in an attempt to stop the spread of epileptic seizures. In the intact brain, however, the working assumption among neuroscientists is that the networks communicate across hemispheres, and so the whole notion of left-right brain in a "normal" person is not significance in real-time. Plus, as fMRI is a recent technology, these results and the conclusions drawn from them are far from conclusive. And how they are interpreted is equally, if not more, important.

Aug. 20 2013 09:45 AM

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