Neuroscientists learn a key rule early in training: exclude left-handed participants from studies. As a result, brain research largely overlooks left-handers. But why this exclusion, and is it justified?
Lyam Bailey, a PhD candidate in psychology and neuroscience at Dalhousie University in Canada, addressed this in a Vice article on July 10, 2020. Many left-handers express frustration over the scarcity of studies open to them.
Left-handers, who comprise about 10% of the population, are routinely excluded from neuroscience protocols—not just those on language or motor skills, but also brain imaging studies like fMRI scans.
Emma Karlsson, a postdoctoral researcher in psychology and cognitive neuroscience at Bangor University in Wales, notes that this exclusion is a fundamental rule taught to students.
Researchers seek comparable data to compute group averages and draw conclusions about brain function. Left-handers' brains, however, differ in key areas like lateralization for language processing and motor tasks.
The brain's two hemispheres aren't perfectly symmetrical. In right-handers, language processing predominantly occurs in the left hemisphere. Left-handers, by contrast, often engage both hemispheres or primarily the right.
Karlsson argues this approach is flawed. Including left-handers could deepen our understanding of hemispheric division of labor and the genetics of brain asymmetries.
