Wolman, a Portland, Ore. freelance, committed a year of his life to traveling the world in order to explore left-handedness — specifically, what causes it and how left-handers might differ from the right-handed majority. Lefties are about 10-12 percent of the population. Wolman's travels took him to see neuroscientists in Berkeley, lefty golf enthusiasts in Japan, psychologists in London, a double amputee in Illinois, palm readers in Quebec, and centuries-old brains in Paris.