There is a nice profile of mathematician Terence Tao in the New York Times magazine this week. Tao is astonishing in his breadth and depth. He could probably master any subject in any field if he just put his mind to it. The article plays up his “normality” in contrast to the stereotype of the eccentric asocial mathematician like Gauss, John Nash or Grigory Perelman, who proved the Poincare Conjecture. However, in my experience, most mathematicians, even the very best, are reasonably normal and sociable. My guess is that the rate of personality disorder among mathematicians is no higher than the general populace. It is perhaps true that mathematicians are more introverted and absent minded than average but rarely to a pathological degree. I think the myth persists because of a few very prominent examples but also that mathematics is a pursuit where having a personality disorder is not a major handicap. One could probably not be a great lawyer, physician or statesman if they were socially abnormal. Thus, if the rate of historically great eccentric mathematicians is high compared to other fields, it is because the sample is biased.