Researchers now, however, are recognizing the scientific importance of understanding why people use one hand or the other to write, eat or toss a ball.
Handedness, as the dominance of one hand over the other is called, provides a window into the way our brains are wired, experts say and it may help shed light on disorders related to brain development, like dyslexia, schizophrenia and attention deficit hyperactivity disorder, or ADHD, which are more common in left-handed people.
Other recent research suggests that mixed-handedness—using different hands for daily tasks and not having a dominant one—may be even more strongly linked than left-handedness to ADHD and possibly other conditions.
About 10% of people are left-handed, according to expert estimates. Another 1% of the population is mixed-handed.
What causes people not to favour their right hand is only partly due to genetics—even identical twins, who have 100% of the same genes, don't always share handedness.
More important, researchers say, are environmental factors—especially stress—in the womb.
Babies born to older mothers or at a lower birth weight are more likely to be lefties, for example and mothers who were exposed to unusually high levels of stress during pregnancy are more likely to give birth to a left-handed child.
A review of research, published in 2009 in the journal Neuropsychologia, estimated that about 25% of the variability in handedness is due to genetics.
On average there is no significant difference in IQ between righties and lefties, studies show, belying popular perceptions.
There is some evidence that lefties are better at divergent thinking, or starting from existing knowledge to develop new concepts, which is considered an element of creativity.
Oddly, left-handed people have salaries that on average are about 10% lower than righties, according to recent research performed at Harvard University that analyzed large income data bases, although findings of some earlier studies were mixed.
Left-handedness appears to be associated with a greater risk for a number of psychiatric and developmental disorders.
While lefties make up about 10% of the overall population, about 20% of people with schizophrenia are lefties, for example.
Links between left-handedness and dyslexia, ADHD and some mood disorders have also been reported in research studies.
Posts
No comments:
Post a Comment