None of it turns out to be simple. The idea of links to schizophrenia has been particularly persistent, but schizophrenia is a complicated and probably heterogeneous disorder, and studies of different populations show different patterns; last year, a study found no increased risk with non-right-handedness for schizophrenia or poorer neurocognition.

In pediatrics, we sometimes worry about children who manifest handedness too early, before their first birthday. The concern is that if a very young child seems to strongly prefer one hand, there may actually be some problem — perhaps some kind of neurological damage — on the other side.

Left-handedness has sometimes been treated as pathological. Cesare Lombroso, the infamous 19th-century physician who identified various facial (and racial) features with criminal traits, also saw left-handedness as evidence of pathology, primitivism, savagery and criminality. And I was brought up with the story that a generation ago, in the bad old days (and in the old country), foolish unenlightened people tried to force left-handed children to convert and use their right hands. My father said that my uncle, his older brother, had had his left hand tied behind his back as a child.

A colleague’s husband, Anthony Gentile, a fund manager who is 41 and grew up outside Cincinnati, told me that though he was always left-handed, he was taught to write with his right hand — though he can form the letters, he could never learn to hold the pencil correctly in that hand. “I can hold the pencil properly in my left hand, but I don’t have the coordination to write,” he told me. “It looks like I’m holding the pencil properly, but I am unable to make any letters.”

The percentage of left-handers in the population seems to be relatively constant, at 10 percent. And this goes back to studies of cave paintings, looking at which hands hunters are using to hold their spears, and to archaeological analyses of ancient artifacts. So though there has been prejudice against left-handers, and though there may be some developmental risks, said Dr. Geschwind, “there clearly must be advantages as well. The reason why it maintains that way, nobody knows what it is.”

Indeed, there seems to be a certain fascination with figuring out the areas (like the presidency) in which left-handers seem to shine. Numbers are sometimes quoted about how many architects are left-handed, or how many M.I.T. professors. On the other hand (so to speak), at a moment when we can finally hope for an end to winter, maybe we should celebrate the left-handers whose greatness truly lies in the ways they integrate motor control, strength and the highest kinds of skill and intelligence. Warren Spahn, Sandy Koufax, Whitey Ford, anyone? C. C. Sabathia, Jon Lester, Cliff Lee?