Left or Right?

Do you play the piano or the violin?—-and are you left- or right- handed?

Those two questions are more related than you might think.

Autistic persons are more likely to be left-handed, Daniel Geschwind, a UCLA expert in what is known as neurobehavioral genetics, notes in an article about the genetics of left-handedness. Among MIT professors, musicians, and architects (Leonardo daVinci among them), there is a slightly higher percentage of left-handers than in the general population. The brains of those who are left-handed develop more “freely” in utero:

In most people, experts say, the left hemisphere of the brain specializes in tasks that are performed in sequence, such as reading and speaking; the right does more holistic processing, like that needed for visual perception. Most people have a dominant left hemisphere, and since each hemisphere controls the opposite side of the body, most of the population is right-handed.

For years, many psychologists assumed that lefties’ brains were reversed, with language capacity concentrated in the right side of the organ. Subsequent work shows that is sometimes the case — but not always.

A large body of research shows the majority of right-handers follow the typical pattern, using the left hemisphere for language. Left-handers’ brains appear less predictable: About half have language abilities concentrated in the left, 10 percent in the right, and 40 percent make use of various regions on both sides.

Many animals are right or left-pawed, or -footed or -flippered. Mice, for example, will consistently use either the right or left paw to press a lever. Unlike humans, however, most species are divided 50-50.

(I guess birds wouldn’t be left- or right- winged?)

My mother-in-law is left-handed—-but can write with both hands, due to being taught (forced) to do so by the nuns in Catholic school (and her writing is pretty much the same, with either hand). My grandfather (on my mom’s side) was ambidextrous. Charlie has been taught to use his right hand to eat with and to use the computer mouse. He definitely has a lot of trouble holding a pencil to write and his letters are loopy and imprecise; he learned to play the piano first with his right hand, and then started to play with his left hand easily. Playing with both hands (and reading music on both the treble and bass clefs) has taken him months to learn. University of Toledo psychologist Stephen Christman, while studying handedness and preference for musical instruments, suggests that it is not so much whether a person is right- or left-handed, but whether they favor using one hand or both that is of interest, and I’ve wondered if Charlie is a “mixed hander”:

People who were very strongly right- or left-handed preferred keyboards and drums, while those who were more ambidextrous gravitated toward strings.

“I realized that maybe what’s important is not left or right but strongly one-handed or mixed,” he says.

There is some evidence, he says, that mixed-handers have a wider connecting pathway — called the corpus callosum — between the right and left hemispheres. Having a wider connection seems to make it harder to do more than one thing at a time — playing a different rhythm with each hand, for example.

Christman has found that strong right- or left-handers, on the other hand, are more likely to hold to set beliefs, such as creationism. He speculates that communication between hemispheres helps people revise beliefs.

I’m right-handed myself and enjoy playing the piano and typing—-and I just took out my viola from the back of a closet.

Photos courtesy of Marcoeusebio (viola) and j-fin (sheet music) via Flickr.