Is it true that left-handed people are smarter than right-handed people?
—Matthew Robison, Concord, N.H.
Chris McManus, professor of psychology and medical education at University College London, responds:
If by intelligent you mean someone who performs better on IQ tests, the simple answer is no. Studies in the U.K., U.S. and Australia have revealed that left-handed people differ from right-handers by only one IQ point, which is not noteworthy.
Left-handedness is, however, much more common among individuals with severe learning difficulties, such as mental retardation. A slightly higher proportion of left-handers have dyslexia or a stutter. Other problems, such as a higher rate of accidents reported in left-handers, mostly result from a world designed for the convenience of right-handers, with many tools not made for left-handed use. Although some people claim that a higher percentage of left-handers are exceptionally bright, large research studies do not support this idea.
If by smarter you mean more talented in certain areas, left-handers may have an advantage. Left-handers’ brains are structured differently from right-handers’ in ways that can allow them to process language, spatial relations and emotions in more diverse and potentially creative ways. Also, a slightly larger number of left-handers than right-handers are especially gifted in music and math. A study of musicians in professional orchestras found a significantly greater proportion of talented left-handers, even among those who played instruments that seem designed for right-handers, such as violins. Similarly, studies of adolescents who took tests to assess mathematical giftedness found many more left-handers in the population. The fact that mathematicians are often musical may not be a coincidence.
For other talents and skills, the benefits of being left-handed are less clear. In one-on-one competitive sports, being in the minority can be a tactical advantage. For instance, most right-handed tennis players have little experience playing left-handers, whereas left-handers have plenty of experience playing right-handers. Sports arenas can also be asymmetric, which may give left-handers an advantage. In baseball, for instance, a left-handed hitter is closer to first base after striking the ball than a right-handed batter is.
Whatever the advantages, handedness seems to be genetic. With 10 percent of people preferring their left hand, there must be some selective advantage, or else the genes would probably not survive.