Psychologists have always assumed that the way emotions are organised in the brain is the same for all of us. But now a new study suggests that left-handers process emotion in the opposite side of the brain to right-handers — which could change the way we think about and treat mental disorders.
The research, carried out at The New School for Social Research in New York and published in PLoS One, looked into how neural activity was distributed for approach motivation — the emotional drive to approach or withdraw from physical and social stimuli. For decades, scientists have believed that approach motivation is processed mainly in the left hemisphere of the brain and withdraw motivation in the right hemisphere.
Using electroencepahlography (EEG) to compare brain activity of participants, the researchers investigated how approach motivation was processed by left-handers and right-handers. The results came as a surprise.
In right-handers, the brain activity was exactly as scientists had previously suspected. In left-handers, however, it was completely flipped: approach motivation was processed in the right hemisphere, not the left. Daniel Casasanto, one of the researchers, explains to Medical Daily:
"Approach motivation is computed by the hemisphere that controls the right hand in right-handers, and by the hemisphere that controls the left hand in left-handers. We don't think this is a coincidence. Neural circuits for motivation may be functionally related to circuits that control hand actions — emotion may be built upon neural circuits for action, in evolutionary or developmental time."
While it might not sound too big a deal, consider this: brain stimulation used to treat conditions like depression and anxiety disorders target specific hemispheres of the brain. Given these results, current treatments might be the exact opposite of useful for left-handers — they could actually be making them worse.
This is a preliminary study, of course, and doesn't show anything casual — but if future studies show the same results, differences in brain function with handedness could change the way we think about emotion for good. [PLoS One via Medical Daily]
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