By YVONNE CURRY
According to a Yale University study, people who are left-handed are at greater risk of psychotic disorders such as schizophrenia. When researchers polled patients at a mental-health clinic, 40% of those with schizophrenia or schizoaffective said they wrote with their left hand; that’s considerably higher than the 10 or 15% of lefties found in the general population. Studies have also found links between non-right-handedness and dyslexia, attention deficit hyperactivity disorder, and some mood disorders.
There is no set figures on how many people are left-handed, but according to the Medical Daily, the estimates run between 10 and 15 percent. Handedness, the term indicating which hand is more dominant, has long been a subject of mystery among scientists as well as superstition in the fellow man – people have even associated lefties with demonism and bad luck traveling. And research hasn’t been able to pinpoint exactly when lefties started to appear.
Ronald Yeo, PhD of psychology, at the University of Texas, says the brains and bodies of lefties may operate differently than those of right-handed people (and in mixed-handed people, who may have different dominant hands for different tasks). “Handedness seems to be determined very early on in fetal development, when a lot of other things about your future are being determined as well,” Yeo says in an interview for Health.com. In one British study, the fetuses of super-stressed pregnant women were more likely to touch their faces more with their left hands than their right. This could be the first signs of a left handed child, say the researchers.
“Most right-handed people use the left hemisphere of their brains to process language,” says Gina Grimshaw, PhD, director of the Cognitive and Affective Neuroscience Laboratory at the University of Wellington in New Zealand. Grimshaw says “right brained” is just a common myth and about 98% of right-handers are left-brained, but so are about 70% of left-handers. Only about 30% are right-brained or bilateral-brained (in which both halves are equally capable). “Most left-handers seem to have similar language processing to right-handers,” Grimshaw says.
Overall, both Yeo and Grimshaw agree that of all the interesting facts about handedness, probably the most important one, is that it doesn’t matter much at all. “The differences between righties and lefties are really rather subtle, and of much greater scientific interest than any kind of practical use,” Yeo says. Grimshaw agrees, noting that mixed-handers seem to differ from “strong handers,” much more than left and right-handers differ from each other. “However, we really don’t know much about the brains of mixed-handers, because we’ve been so focused on the left-handers,” Grimshaw says. Yeo says, “We shouldn’t assume much about people’s personalities or health just because of the hand they write with. And we certainly shouldn’t worry about lefties’ chances of success. After all, as of 2015, five of our last seven U.S. presidents have been either left or mixed-handed.”