A Handful of Scientific Facts About Lefties

— -- intro: Today is International Left-Handers Day. On the one hand, let’s celebrate the 10 percent or so of the population that favor their left hands for important tasks. On the other hand, this is the perfect time to toss out five little-known scientific facts about lefties.

quicklist: 1category:title: Lefties can throw a punchurl:text: When researchers at the University of Montpellier in France surveyed nine primitive societies in five separate continents, they found a higher percentage of lefties translated into more frequent violent encounters. Furthermore, lefties often had the upper hand in a fight because of the element of surprise. No one expects a punch to come out of left field.

This same sneak attack seems to cross over into a sports advantage, the researchers speculated, especially in sports like boxing, tennis and fencing where opponents go head-to-head.

quicklist:2category:title: Animals have a paw preference, toourl:text: One British study, among others, found that about 40 percent of cats are southpaws, with an additional 10 percent happy to swat a ball of yarn with either paw. Another Brit study found paw preference in dogs is split about evenly.

It seems Fido takes sides with his tail, too. Last year, an Italian study suggested that when dogs wag their tails from right to left, it signifies happiness. Wagging from left to right demonstrates displeasure.

quicklist: 3category:title: We love leftie leadersurl:text: The fact that five of our last seven commanders in chief have been lefties is probably a coincidence. However, as one recent Dutch investigation suggested, right-handed politicians may want to fake it to the left.

Left-handed people tend to raise their left hands when speaking about something good whereas right handers tend to raise their right hand. But in televised debates, when a person raises his or her right hand, it will appear on a viewer's left, just as if the person was sitting in a chair in front of them. For this reason, viewers subconsciously interpret left-hand movements as good and right-hand movements as bad.

quicklist: 4category:title: Lefties use their brains differentlyurl:text: Lefties may use their noggins slightly differently from righties, the research suggests. For example, one Australian study found left-handed people access both hemispheres of their brain more readily than right-handed people, who tend to be left hemisphere-dominant.

There are advantages and disadvantages to using the brain with a more even distribution. Some studies find lefties to be more creative and more resilient when recovering from strokes. However, other studies imply lefties are more susceptible to ADHD, schizophrenia and other mental disorders.

quicklist: 5category:title: Lefties are often left outurl:text: Scissors and computer mice were designed without a second thought for lefties. That’s inconvenient. But leaving left handed people out of the equation in scientific research may have far-reaching consequences, Dutch scientists have said.

Writing in the journal Nature earlier this year, the scientists pointed out that left-handed people have different brains and genes from right-handed people, yet are rarely included as study subjects. As a result, we may be missing out on important information in everything from neuroscience to genetic disorders, the scientists said.