[MRM]

Actually, I've read that Lincoln's IQ was estimated at 115 - bright normal. That probably underestimates his mental capabilities. In the last 20 years or so archivists have found old court records from cases he handled as a lawyer. They show unusually complex and successful legal arguments, often on behalf of railroad companies. Railroads were the big business of the day and could pay for the top legal talent. Rather than being a stumbling poor country lawyer, he was probably a very sharp and shrewd person. Now he was probably mentally ill, and his wife certainly was, but he was a smart guy.

Contrast him to FDR who even his advisors considered stupid. One of his people called him a second rate intellect with a first rate demeanor. Meaning that you can be great at what you do without a high IQ, as long as you have the social skills necessary to harness the horsepower you do have. Kind of like low-power/lightweight racecars being competitive with big horsepower brutes.

That's why I think IQ "studies" like this are useless at best and misleading at worst. Intelligence is three dimensional and IQ tests measure one dimension of intelligence. Besides, there is no long-term correlation between intelligence and genetics. Over time everyone's decedents regress to the mean. Smart people have dull children, geniuses are born in slums. Intelligence, like rain, falls on the just and unjust, rich and poor, equally.