I found a rather interesting book this weekend that had a chapter on this very subject. The book is "Brains That Work a Little Bit Differently", by Alan D. Bragdon and David Gamon, PhD. It gives brief overview on various things like left-handedness, dyslexia, and even synesthesia. A bit dumbed down for my tastes, but readable. If it interests you, you can order it from the Oregon Museum of Science and Industry OMSI or by calling the OMSI bookstore at (503) 797-4626.
~JE