Demystify science | The consequences of the repressed leftrs

Each week, our journalist answers scientific questions from readers.

The question is topical, since August 13 was International Left Day, launched in 1976 by an American veteran, Dean R. Campbell.

The superior intelligence of left -handers is a myth, but there would be more geniuses and a greater proportion of certain neurological problems in left -handers, according to studies on the subject.

For the left -handers that we forced to write with the right hand, no study has measured the consequences that this could cause. But according to a German psychologist who wrote a book on the issue, they would more often have problems of memory, spelling, concentration and self -esteem.

“I have treated thousands of leftrs for three decades for three decades that have forced to write with the right hand,” says Barbara Sattler, author of the book The Converted Left-Handerwhich has just been published in English, 30 years after its publication in German. “In Germany, we started to question this practice in the 1980s, but it was only since the new millennium that it is officially discouraged in all regions. »»

Are you a left-hander who was forced to write with your right hand? Let us know your experience

M^me Sattler, whose left -handed help center is in Munich, has also set up training to help the occupational therapists.

“As they get older, the left-hander, whether or not he was forced to write with the right hand, has cognitive and physical limitations a little different from those of right-handers,” she illustrates.

M^me Sattler gave his 100 -hour training to almost a thousand caregivers.

Autism and deafness

As for neurocognitive differences between left-handers and right-handers, the Greek researcher Marietta Papadatou-Pastou is among those who worked the most on the subject. The neuropsychologist at the University of Athens notably compared left-handers and right-handers in terms of intelligence, but also the prevalence of autism, deafness, attention deficit (ADHD) and the severity of post-traumatic stress syndrome, among others. In each case, there was no gap between left -handers and right -handers.

This greater neurological variability, however, remains to be confirmed.

Barbara Sattler has not studied distinctions between left -handers and right -handers, but she believes that neurological differences must necessarily have effects. “In right -handers, 96 % of people use the left half of their brain to speak,” says M^me Sattler. In left -handers, this proportion is 72 %. It is difficult to understand the neurological impacts of this difference, but there are certainly. Some data seem to show that there is a greater prevalence of language disorders, for example dyslexia. But then again, it remains to be confirmed with other studies. »»

There is not much funding for studies on these issues, deplores Marietta Papadatou-Pastou. For example, there is no official definition of the terms “right -handed” and “left -handed”. Some researchers are based on patient declarations, others on the hand with which they write, and still others on the relative force of both hands.

Nevertheless, the Greek neuropsychologist managed to study the preference of mothers to rock their baby (usually the left hand), the link between the feet and hands in the left -handers (they have the left left foot) and the situation in cats and dogs (about the quarter are ambidextrous and right -handers are not more numerous than left -handed).

Do you have a scientific question? Write us