Approximately 10 percent of the world's population is left-handed. Notably, although most people use their right hands for performing tasks such as writing, approximately 30 percent of the population is mixed handed, which means that they change their hand preference between tasks.
Although science isn't completely sure what causes a person be left- or right-handed, experts believe that a combination of genes and a person's environment determines which hand is dominant. People who are dominant in the use of their left hand usually have left-handed family members.
Scientific studies have shown that lefties are at a greater risk for psychosis, are more likely to be elected to office and are better attuned to sports. They are also more prone to drinking and are more easily embarrassed than their right-handed counterparts; folks who are "southpaw" tend to anger more easily than those who are right-handed.
Notable left-handed people include: Bill Gates, the founder of Microsoft and one of the richest people in the world, painter Leonardo da Vinci, artist Vincent Van Gogh, military leader Alexander the Great, Cuban leader Fidel Castro and Helen Keller. Interestingly, Joan of Arc is thought to have been left-handed.