Left-handed people comprise about 10 percent of the population, but the reason for left-handedness is uncertain. Genetics is about 25 percent responsible, according to a study published in 2009 in the journal Neuropsychologia. Babies with low birthweights are more likely to be left-handed as are babies born to older mothers and to mothers who were under high levels of stress during pregnancy.
Left-handed people have IQs similar to their right-handed counterparts, but a Harvard University study revealed that left-handers earn about 10 percent less than right-handed people. Lefties tend to excel in divergent thinking, often selecting careers in the arts, music, sports and information technology. Author H.G. Wells, musicians Jimi Hendrix, Paul Simon and Ringo Starr, artist Michelangelo, and actors Judy Garland, Angelina Jolie, W.C. Fields and Tom Cruise are examples of some famous left-handed people in creative fields.
Dyslexia, schizophrenia and attention deficit hyperactivity disorder are more common in left-handed people. A study by Yale University and the University of Texas Southwestern Medical Center found that 40 percent of the subjects who suffered from psychosis, such as schizophrenia, were left-handed.
A study that appeared in The Journal of Nervous and Mental Disease indicated that lefties find it more difficult to process their feelings and often display more negative emotions. A study conducted by Abertay University in Scotland concluded that left-handed people tend to be more shy, become more easily embarrassed and are more inhibited than those who are right-handed.