Left vs. Right

Left-handers have long been a source of intrigue for researchers. Over the past several years, there have been numerous studies on what causes people to be left- or right-handed and whether there are differences in skills and intelligence.

A Wall Street Journal article in December 2011 cited research that whether someone is left or right-handed is due more to environmental rather than genetic factors. The article noted that mothers who were older or exposed to high stress levels while pregnant were more likely to have left-handed children. Babies born at a lower weight also had a higher incidence of being left-handed.

Dr. Alan Searleman of St. Lawrence University in New York, who researches left-handedness, found that left-handers have higher IQs and a more extensive vocabulary than right-handers. But more studies have shown there is no difference in intelligence between left- and right-handed individuals, although researchers at Harvard University discovered that left-handers earn 10 percent less than right-handers, the Wall Street Journal reported.

Other more recent studies also discussed in the Wall Street Journal have discovered that left-handed people have an increased risk of psychiatric and brain development disorders, including bipolar disorder, dyslexia, schizophrenia and attention deficit hyperactivity disorder, or ADHD. According to researchers, left-handers, who comprise about 10 percent of the population, make up 20 percent of those individuals with schizophrenia.

Why there should be any difference between left- and right-handers is not clear - but a 2006 study by Australian National University supports previous research showing that left-handers process certain functions, including language, using both hemispheres of the brain. Right-handers primarily use the left hemisphere for this activity.

Further studies show that compared to right-handers, left-handers are better at divergent thinking, and therefore, more creative; have an advantage at certain sports, including tennis and baseball; and are faster at processing multiple stimuli.

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