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.
More research is needed to establish a link between ADHD and
mixed-handedness. However, some evidence suggests that ADHD is associated with
a weaker functioning of the right side of the brain. Mixed-handedness may also
be related to that side of the brain.
The study authors say their findings could help teachers and health
professionals develop methods to identify children who may have problems with
learning, language, or behavior issues in the future. “Mixed-handedness,
particularly in the presence of difficulties, could aid in the recognition of
children who are at risk,” Alina Rodriguez, PhD, and colleagues write in the
They caution, however, that the results do not mean that all mixed-handed
kids will have problems at school or develop ADHD. Mixed-handedness is rare,
and the number of children in their study with this trait was small.