Jan. 25, 2010 -- Young children who can eat, write, and perhaps throw a ball with both hands are more likely to develop learning, language, and mental health problems than children who are strictly right- or left-handed, according to a new report in the journal Pediatrics.
The ability to write and perform other tasks with both hands is called mixed-handedness. About one in every 100 people is mixed-handed, or ambidextrous. What makes a person ambidextrous is somewhat of a mystery, but the ability has been linked to the hemispheres of the brain.
The brain is split into two halves: The left side, or left hemisphere, and the right side, or right hemisphere. Studies have shown that when people naturally gravitate toward using their right hand, the left hemisphere of the brain is more dominant. In mixed-handed people, it appears to be less clear that one side of the brain is more dominant over the other.
For the current study, researchers from the Imperial College London and other European institutions evaluated nearly 8,000 Finnish children, including 87 mixed-handed children, to determine if mixed-handedness was associated with any potential difficulties in school.
When the children were 8 years old, their parents and teachers answered questions regarding their behavior, ability to learn and speak words, and school performance. The teachers disclosed if the child had any reading, writing, or math difficulties and graded each child’s academic performance as below average, average, or above average.
When the children turned 16, they completed a survey regarding how well they thought they did in math and language compared to their classmates. Their parents filled out a behavior-related questionnaire used to identify attention deficit hyperactivity disorder (ADHD) symptoms.
The questionnaires showed that mixed-handed 7- and 8-year-olds are twice as likely as their right-handed classmates to perform poorly in school.
Mixed-handed children aged 7 and 8 were twice as like as right-handed children to have language problems such as dyslexia. (This finding upholds previous research linking mixed-handedness with dyslexia.)
Mixed-handed children were twice as likely to develop symptoms of ADHD later in their teenage years, about age 15 or 16.
Mixed-handed children were more likely to have more severe ADHD symptoms than right-handed children.