If we were to take the average IQ of those who have earned a Ph.D. (as opposed to honorary Ph.D.’s) we would find that it would be significantly higher than average because it would contain the IQ’s of some of the brightest people on the planet.
In 2001, Lubinsky et al* published a study of 320 profoundly gifted 13-year olds (estimated IQ’s around 180) 10 years after they were identified as profoundly gifted, to determine the extent to which their intellectual potential was manifest in educational attainment. They found that 56% of this group had achieved or were seeking a Ph.D. degree. This compares with only 1% of the general population who pursue a Ph.D. degree. Those who are gifted (IQ of 130 or more) rather than profoundly gifted, are 25 times more likely than the general population to pursue a Pd.D degree. The table below from that study, shows the percentages of the profoundly gifted who aspired to a bachelor’s degree (column B), a master’s degree (column M) and a doctoral degree (column D). These data are presented for three groups: High math ability, High verbal ability, and equally-balanced abilities (High-flat).
*David Lubinski, et al. (2001) Top 1 in 10,000: A 10-Year Follow-Up of the Profoundly Gifted. Journal of Applied Psychology Vol. 86, No. 4 718-729.
Clearly, the pool of Ph.D. candidates is richly salted with those of high to very high IQ. However, there are significant differences in intelligence among those who have a Ph.D. according to the subject discipline and the degree-granting university. The table above shows that a large proportion of the profoundly gifted aspire to doctoral degrees in the inorganic and organic sciences. The figure below from the College Board gives the average SAT score by college major for the year 2014.
We see that the highest average SAT scores are earned by those in the STEM subjects, while the lowest are in agriculture and education. The high correlation between IQ and SAT scores, suggests that there are significant differences in the average IQs of those who receive doctorates in different fields.
Of course, the graph shows averages, so a person in one of the disciplines of lower average IQ might have an IQ higher than many people in the higher IQ category. Therefore, we have to judge each person individually. Yet, we cannot assume that a person is highly intelligent merely because they have a Ph.D. As one of my friends once said about himself, “Dr. Einstein and I have Ph.D.’s, in physics, but that’s where the comparisons end.”
