Why are most left-handers ambidextrous

News portal - Ruhr University Bochum

One thing has always been clear: left-handed people are less common than right-handed people. But how many people really prefer the left hand has only now been clarified: the left-handed rate is 10.6 percent. This was the result of the world's largest study on this subject, in which a research team from the Universities of St. Andrews, Athens, Oxford, Bristol and Bochum evaluated studies on the handedness of a total of more than two million people. The results are published in Psychological Bulletin April 2, 2020.

The severity of the criteria influences the quota

For the current study, the researchers, to whom private lecturer Dr. Sebastian Ocklenburg from the Faculty of Psychology at RUB performed five meta-analyzes, which included the data from a total of 2,396,170 people who had to perform various manual tasks in studies. "How often left and right-handed people are in each case also depends on how strict the criteria are that the authors apply," explains Sebastian Ocklenburg.

If the strictest criteria are used, 9.34 percent of the test subjects are left-handed. If less strict criteria are used, 18.1 percent are not right-handed. "The best overall estimate is 10.6 percent left-handedness," said Ocklenburg.

Writing isn't everything

Usually the handedness is made dependent on which hand someone writes with. In the current study, however, the research team took into account the fact that around nine percent of people use different hands for different tasks. That made for more accurate results. "According to the data, the proportion of people who use different hands for different tasks is almost as large as the proportion of left-handed people," emphasizes author Dr. Silvia Paracchini from the St. Andrews School of Medicine.