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Does Being a Lefty Affect Health, Creativity -- and Sexuality?

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Sept. 8, 2000 -- The desks in grade school, the notebooks, the penmanship lessons. For those who are left-handed, life is an adaptive process that begins early. Says one friend, "Teachers tell you, 'Use the hand you eat with.' I did! But they kept wanting me to use my right hand."

Lefties grow up feeling different, and eventually treasure their uniqueness. Browse the Internet and you will find hundreds of famous lefty names: Leonardo da Vinci, Ringo Starr, Babe Ruth, Albert Einstein. A whole tennis tournament: Martina Navratilova, Monica Seles, John McEnroe, Jimmy Connors. Even Jack the Ripper was a leftie. Who knew?

What causes us to be left- or right-handed? And do lefties really have a greater risk of certain disorders and diseases, as some studies have shown? Are lefties more creative? Can being left-handed even influence sexual orientation -- as a new study suggests?

Or are lefties wired very much like the rest of us and at no greater risk of anything simply because they favor the left hand, as Paul Satz, PhD, chief of the neuropsychology program at UCLA's Neuropsychiatric Institute, tells WebMD.

The debate goes on. Case in point: In the August issue of the journal Psychological Bulletin, researchers report finding a "significant" relationship between handedness and sexual orientation. Compared with heterosexual participants, gays had 39% greater odds of being non-right-handed, writes study author Martin L. Lalumière, a researcher in the Centre for Addiction and Mental Health at the University of Toronto.

Handedness is observed quite early in development. Left-handedness is more common in men than in women, and tests of fetuses (using ultrasound) show 92% sucking their right thumbs, a figure that mirrors prevalence in the adult population, writes Lalumière.

What causes us to be left- or right-handed, however, is undecided. Here are the theories:

  • Genes. Much research points to a genetic influence, yet studies of twins have complicated that theory. Whereas identical twins have identical genes, an analysis of 13 identical and fraternal twin studies -- ranging from 1933 to 1985 -- showed that only 76% (of the expected 100%) of identical twins are both left-handed.
  • Too much fetal testosterone. One theory suggests that high levels of testosterone in the uterus -- possibly caused by stress during pregnancy -- damage or slow the development of the normally dominant left half of the brain, causing some functions to shift to the right half of the brain, which governs visual-spatial, creative abilities like math, music, art, and architecture. Lefties were considered at higher risk of immune diseases, since high testosterone levels can inhibit immune system development. This theory has largely been disproven.
  • Developmental instability in the uterus. Some researchers now think that something indeed happens to change the fetus' "ecological environment" during pregnancy, something that governs handedness and brain organization in general. Although they have not yet figured out the mechanism, they feel that the fetus' vulnerability to environmental stressors -- things that cause disease, like bacteria, pollutants, and stress during pregnancy, as well as genetic mutations -- can cause this instability.

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