The Probable Highest IQ Among 19th-Century Geniuses

    Using a log-normal model--which fairly well fits the IQ distribution observed by Terman and his colleagues in 1921--ratio IQs might be expected to go as high as about 250, with an expected frequency of about 1 in 1,000,000,000. However, a ratio IQ of 200 would correspond to a deviation IQ of 174, and a frequency of occurrence of about 2 per 1,000,000. It's possible that one or two of the cited 19th century geniuses might have had ratio IQs a little in excess of 200, but by and large, they would have had ratio IQs below 200, and present-day Raven-derived IQs below 100!