Monday, January 25, 2010
Researchers say that ambidextrous children are at greater risk of difficulties at school, language problems, and disorders such as attention-deficit hyperactivity disorder (ADHD) than those who are left-handed or right-handed. Dr Alina Rodriguez, from the School of Public Health at Imperial College, London, and a team of researchers from various European universities studied nearly 8,000 children from the north of Finland; 87 of these were ambidextrous (mixed-handed). Parents, teachers and the children themselves assessed language skills, academic achievement and behaviour. At ages 7 and 8, the ambidextrous children had double the rate of language problems and were twice as likely to have problems at school. At age 15 and 16, the proportion of those with ADHD symptoms was twice as many in the ambidextrous group, and their ADHD symptoms tended to be worse. Ambidextrous children in the study also had a higher rate of language problems.
The number of people who are ambidextrous is unclear, with estimates ranging from 1% to 5%. Scientists do not know why some people use both hands when the majority of people prefer to use one predominantly. The theory is that there is something different in the brains of ambidextrous people, although Rodriguez says that more work in the area is needed.
A person who prefers using their right hand will have a more dominant left hemisphere of the brain, which is the part of the brain for language skills. Rodriguez and her researchers have suggested that the right hemisphere of the brain of an ambidextrous child is weaker compared to that of a right-handed child, increasing their susceptible to problems with attention. Previous suggestions about the causes of ADHD include the possibility that a person’s right hemisphere has weaker function. Earlier studies have drawn links between dyslexia and being ambidextrous, and other studies are looking at the part that differences between the two sides of the brain play in language skills and psychosis.
Rodriguez emphasised that the research, published in the journal Pediatrics in the United States, did not show that all ambidextrous children would have such problems, pointing out that most of the children in the survey did not develop them. “Our study suggests that handedness is really a marker for atypical foetal brain development — showing that the brain is working in a different way to the norm”, she said, adding that other studies have shown atypical brain development to be associated with extraordinary creativeness. She also suggested that the results may assist schools and health care workers in targeting children at risk of problems.