One of the first things that anatomy students learn is that the brain is divided down the center. In most people, one half, or hemisphere, plays a dominant role. Handedness has long been a crude measure of hemispheric dominance, because each side of the brain controls the opposite side of the body. Right-handers, for instance, are likely to have dominant left hemispheres. Today researchers are realizing that studying ambidextrous children (who have no dominant hand) could yield insights into the consequences of an unusually symmetrical brain.

A team of European researchers recently assessed nearly 8,000 Finnish children and showed that mixed-handed children are at increased risk for linguistic, scholastic and attention-related difficulties. At age eight, mixed-handed kids were about twice as likely to have language and academic difficulties as their peers. By the time the children were 16, they also were twice as likely to have symptoms of ADHD—and their symptoms were more severe than those of right- or left-handed students.

Ambidexterity is not causing these problems. Rather “handedness is really a very crude measure of how the brain is working,” says Alina Rodriguez, a clinical psychologist at King’s College London and the study’s lead author. In typical brains, language is rooted in the left hemisphere, and net­works that control attention are anchored in the right—but brains without a dominant hemisphere may be working and communicating differently.

Consistent with this theory, a 2008 study by scientists at the University of California, Los Angeles, found anomalies in cross-hemisphere communication in children with ADHD. On tasks that should be the domain of the left hemisphere—such as linguistic processing—children with ADHD seemed to be getting too much input from their right hemispheres. Rodriguez is quick to point out, however, that mixed handedness does not, by itself, indicate a malfunctioning brain and is “just one risk factor among many others.”

So why do some kids have overly symmetrical brains? The answer may lie in epigenetics—the mechanism by which environmental influences affect gene expression. In 2008 Rodriguez found that women who experienced stressful life events or depression during pregnancy were more likely to give birth to children who became mixed handed, adding evidence to the idea that the experiences of a mom-to-be affect her fetus’s brain development. [For more about prenatal influences on mental health, see “Infected with Insanity,” by Melinda Wenner; Scientific American Mind, April/May 2008.] That means that handedness, Rodriguez says, “can be used with other markers to predict who’s going to have problems with behavior” and give parents, teachers and doctors the opportunity to intervene at the first sign of trouble.

This article was originally published with the title Ambidexterity and ADHD.

5 Comments

1. 1. helen carlson 12:41 PM 8/7/10

   I am 57 years old and definately ADD. I consider myself to be "other handed" I do just as many things right handed as I do left handed and dare not mix them up i.e. spatula left hand, bowling left hand, writing right hand, tennis left hand, remote control right hand. As a small child when anyone saw me handle my spoon or fork with my left hand, it was immediately corrected to my right hand. I have always thought I was propably suppose to be left handed and forced to be right handed. Has anyone researched this aspect?

   Reply | Report Abuse | Link to this

2. 2. douglasPeter 11:20 PM 8/9/10

   the article didnt explain the genetics that show if you have the right handed gene, your left hemisphere will be dominant, but lacking this gene the hemispheres will compete for dominance or organize differently..
   
   Lacking this gene you have a 50/50 chance of becoming left handed..My whole family is this way and yet half of us are right handed. The behavior is clear..I wouldnt identify it with ADHD but more like mild dyslexia.
   
   The research was done by Geshwind of the original brain lateralization work, and also leftie..of the Geshwind-Warneke team.

   Reply | Report Abuse | Link to this

3. 3. douglasPeter 11:22 PM 8/9/10

   PS its definitely. also a sign of your mental organization, and the lefty can be converted to right handed much easier than the righty to left, because of the tendency to ambi they usually have anyway.

   Reply | Report Abuse | Link to this

4. 4. ambidextrous man 10:21 AM 8/11/10

   Ambidexterity is great to do, be its twice as strong as 1 handed and twice as fast to do Ive been ambidextrous 19/49 years its so much easier being 2handed in life

   Reply | Report Abuse | Link to this

5. 5. Spin-oza 01:42 PM 8/15/10

   Well... for what it's worth... 2 of my 3 children are either left handed or ambidexterous... and both of these 2 have ADD +/- HD. No such tendencies with the righty. I am overtly right handed and was allegedly very hyperactive as a very young child, but no history of ADD... but that was before it was on everyone's radar.
   
   Pharmacotherapy has been instrumental for both of these children at certain stages of their maturation. Which raises all sorts of questions regarding the "creativity" of the ADD brain flitering in and out of mundane normalcy... on a much more restrained scale versus an autistic "savant".
   
   One of evolutions paths was to compartmentalize function in our limited bony cranium and it appears the ADHD brain tends to be less specialized in a hemispheric sense. Whether this is on-balance "pathologic" is entirely an open question and would hinge on the severity of the effect ... inhibiting one's ability to function in a sociologic context.
   
   It is an interesting corrolation that gives neuroscience additional insight on the vast network of synaptic traffic that makes us exactly who we are.

   Reply | Report Abuse | Link to this