They’ve been vilified throughout history as gauche, sinister and wrong-headed. So what is the truth about lefties? It turns out there is little consensus among scientists about what causes handedness or what it means to be a southpaw. Some researchers believe the trait comes down to genetics. Others propose that environmental factors or brain trauma at birth might be at the root of the behaviour. We spoke to some of the few scientists digging into the causes and effects of being a lefty in a right-handed world:
Dr. Pamela Bryden is a professor of kinesiology at Wilfrid Laurier University in Waterloo. She's found that lefties were definitely more flexible and adaptable when she measured their abilities to perform tasks with their non-dominant hand.
Dr. Amar Klar is a geneticist at the National Cancer Institute in Maryland. Dr. Klar decided to study left-handedness by heading to a shopping mall to study the hair whorls on the tops of shoppers' heads. That study led him to believe that most people inherit a single dominant gene for right-handedness, but without that gene, a person has a 50 per cent chance of being a left-hander.
Dr. Chris McManus is a professor of psychology at University College London and author of Right Hand, Left Hand: The Origins of Asymetry in Brains, Bodies, Atoms and Cultures. He believes there is a gene for right-handedness. But he thinks an evolutionary quirk occurred tens of thousands of years ago that caused a gene mutation, which Dr. McManus calls the "chance gene". It cancels the bias to the right, so those who inherit it have a 50-50-chance of ending up lefties.
Dr. Ira Perelle is a professor in the department of psychology at Mercy College in New York. He believes there are at least three possible causes for left-handedness, including the possibility that at a very young age, a child can learn the behaviour.
