During their training, neuroscientists learn an amazing rule of thumb:including left-handed people in brain research is wrong. In other words, neuroscience ignores lefties most of the time! Why such exclusion? Is this an error?
Lyam Bailey is a PhD candidate in psychology and neuroscience at Dalhousie University (Canada). The person concerned, interviewed in an article published by Vice on July 10, 2020, indicates that a large portion of left-handed people are frustrated. The reason lies in the too small amount of studies in which these people can participate.
Indeed, left-handed people are overwhelmingly excluded from brain research protocols. And yet, left-handed people represent about 10% of the population . Moreover, not only are left-handed people excluded from neuroscience research on language or motor skills, but the latter are also excluded from research on brain imaging, in particular those involving brain scans.
As Emma Karlsson, postdoctoral researcher in psychology and cognitive neuroscience at Bangor University (Wales), explains, this exclusion is part of the ground rules learned by students.
It turns out that researchers prefer to work on topics that can be compared to each other. The objective is to be able to make averages by group and thus be able to draw conclusions on the overall functioning of the brain. But the fact is that left-handed people's brains work differently, at least when it comes to certain tasks. It is particularly a question of lateralization, which can for example be relating to the processing of language or motor skills.
As a reminder, two hemispheres make up the brain. However, the anatomy between these two hemispheres is not completely identical . For example, at the level of language, one of the two hemispheres takes on most of the work. In the case of right-handers, most language processing takes place in the left hemisphere of the brain. On the other hand, left-handers use both hemispheres at the same time or only the right.
For Emma Karlsson, this is a mistake. The interested party believes that including left-handed people could allow us to learn more about how the brain works. For example, we could better understand the division of labor by the left and right hemispheres and learn more about the genetic aspect of brain asymmetries.
