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Monday, July 07, 2008

Annals of psychometry: IQs of eminent scientists

[ See this 2013 post for the identities of the 64 scientists. ]

I recently came across a 1950s study of eminent scientists by Harvard psychologist Anne Roe: The Making of a Scientist (1952). Her study is by far the most systematic and sophisticated that I am aware of. She selected 64 eminent scientists -- well known, but not quite at the Nobel level -- in a more or less random fashion, using, e.g., membership lists of scholarly organizations and expert evaluators in the particular subfields. Roughly speaking, there were three groups: physicists (divided into experimental and theoretical subgroups), biologists (including biochemists and geneticists) and social scientists (psychologists, anthropologists).

The Making of a Scientist devotes only one chapter to psychometrics. The other chapters describe the motivation for the study, how the 64 scientists were selected, interviews with the scientists, details of their family history, work life, etc.

Roe devised her own high-end intelligence tests as follows: she obtained difficult problems in verbal, spatial and mathematical reasoning from the Educational Testing Service, which administers the SAT, but also performs bespoke testing research for, e.g., the US military. Using these problems, she created three tests (V, S and M), which were administered to the 64 scientists, and also to a cohort of PhD students at Columbia Teacher's College. The PhD students also took standard IQ tests and the results were used to norm the high-end VSM tests using an SD = 15. Most IQ tests are not good indicators of true high level ability (e.g., beyond +3 SD or so).

Average ages of subjects: mid-40s for physicists, somewhat older for other scientists

Overall normed scores:

Test (Low / Median / High)

V 121 / 166 / 177

S 123 / 137 / 164

M 128 / 154 / 194

Roe comments: (1) V test was too easy for some takers, so top score no ceiling. (2) S scores tend to decrease with age (correlation .4). Peak (younger) performance would have been higher. (3) M test was found to be too easy for the physicists; only administered to other groups.

It is unlikely that any single individual obtained all of the low scores, so each of the 64 would have been strongly superior in at least one or more areas.

Median scores (raw) by group:

group (V / S / M)

Biologists 56.6 / 9.4 / 16.8
Exp. Physics 46.6 / 11.7 / *
Theo. Physics 64.2 / 13.8 / *
Psychologists 57.7 / 11.3 / 15.6
Anthropologists 61.1 / 8.2 / 9.2

The lowest score in each category among the 12 theoretical physicists would have been roughly V 160 (!) S 130 M >> 150. (Ranges for all groups are given, but I'm too lazy to reproduce them here.) It is hard to estimate the M scores of the physicists since when Roe tried the test on a few of them they more or less solved every problem modulo some careless mistakes. Note the top raw scores (27 out of 30 problems solved) among the non-physicists (obtained by 2 geneticists and a psychologist), are quite high but short of a full score. The corresponding normed score is 194!

The lowest V scores in the 120-range were only obtained by 2 experimental physicists, all other scientists scored well above this level -- note the mean is 166.

My comments:

The data strongly suggests that high IQ provides a significant advantage in science. Some have claimed that IQ is irrelevant beyond some threshold: more precisely, that the advantage conferred by IQ above some threshold (e.g., 120) decreases significantly as other factors like drive or creativity take precedence. But, if that were the case it would be unlikely to have found such high scores in this group. The average IQ of a science PhD is roughly 130, and individuals with IQs in the higher range described above constitute a tiny fraction of all scientists. If IQ were irrelevant above 130 we would expect the most eminent group to have an average similar to the overall population of scientists.

Conversely, I think one should be impressed that a simple test which can be administered in a short period of time (e.g., 30 minutes for Roe's high-end exams) offers significant predictive power. While it is not true that anyone with a high IQ can or will become a great scientist (certainly other factors like drive, luck, creativity play a role), one can nevertheless easily identify the 95 percent (even 99 percent) of the population for whom success in science is highly improbable. Psychometrics works!

The scores for theoretical physicists confirm an estimate made to me by a famous colleague many years ago, that only 1 in 100,000 people could do high level theoretical physics.

Feynman's 125: in this context one often hears of Feynman's modest grade school IQ score of 124. To understand this score we have to remember that typical IQ tests (e.g., administered to public school children) tend to have low ceilings. They are not of the kind that Roe used in her study. One can imagine that the ceiling on Feynman's exam was roughly 135 (say, 99th percentile). If Feynman received the highest score on the mathematical portion, and a modest score of 115 on the verbal, we can easily understand the resulting average of 124. However, it is well known that Feynman was extremely strong mathematically. He was asked on short notice to take the Putnam exam for MIT as a senior, and received the top score in the country that year! On Roe's test Feynman's math score would presumably have been > 190, with a correspondingly higher composite IQ.

I thought I should put this post up now, as the new book by Malcolm Gladwell, Outliers: Why Some People Succeed and Some Don’t is out soon and will surely handicap the discourse on this subject for years to come :-)

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