Créditos de imagem: Robert Morin AFP.
There has been a belief that ambidextrous children, those who have shared dominance, who can do things like writing and playing ball games with both hands, are likely to have learning difficulties at school, and to suffer of attention deficits. That was the finding of scientists from Imperial College London, who also found them more likely to have difficulties with language. The study published in Paediatrics in 2009 was commented upon by the BBC.
That does not tie up with neurological prediction. Some 1% of people are of shared dominance, but many more may be of partial shared dominance, and it runs in families. In this Finnish study, of 8,000 children only 87 were selected because of pure mixed-handedness They were twice as likely as the right-handed to have difficulties with language and learning difficulties, as well as twice as likely to develop attention deficit and hyperactivity disorder at 15 or 16 years of age.
When they reached 15 or 16, mixed-handed adolescents who had been ambidextrous children were also at twice the risk of having symptoms of Attention Deficit Hyperactivity Disorder, as well as dyslexia. It may all come to subject selection; classical neurology and neuropsychology would predict that shared dominance may lead to a higher intelligence in tests like WAIS and WISC. Kids would have been exposed to more situations and developed more brain circuits. That is the reason why neurologists instruct the elderly to play snooker or ping-pong with the non-dominant hand to increase cognitive reserve and delay the onset of Alzheimer’s disease.
The left hemisphere of the brain is called dominant because classical thought worked with the paradigm that language was a more noble function than the emotions and time and spatial control located in the right hemisphere. There may be other explanations for the study results, as most of the mixed-handed children did not have any problems, and northern Finland is a highly specific part of the world, on the border with Lapland, and it may be the Santa Claus effect, too much cold, dark and indoor activity, with frequent alcoholism. The BBC paper veers into the realm of mental disease, which again indicates the prevalence of preconceived ideas, which are nowadays handled with the scientific facts of Theory of Mind, the brain circuit that is frankly bilateral, without the least respect of left-sided, verbal dominance. It is high time to recognize that ambidextrous children may be at a clear advantage.
Dr. Paulo Bittencourt