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Senior Vice-President for Research and Innovation, Professor of Theoretical Physics, Michigan State University

Monday, December 12, 2005

Physics still pulls them in...

There is much concern among physicists that our field is no longer getting the same share of the brightest students as in the glory days (e.g., during the cold war). I was pleased to find here that average GRE-general scores in physics PhD programs were still the highest as of 2002, with math and CS close behind. According to these tables, the average IQ of a physics PhD student is about 130. For comparison, english/literature PhD students average about 120 and sociology PhD students only 115. (115 is the average for college students in general, so the typical sociology TA is no smarter than the students in his or her class ;-) Amazingly, the average grad student in education (109) is below the average for college students!

You may find it odd that I converted the results from GRE score to IQ, widely regarded by the politically correct as a discredited measure of intelligence. For a rebuttal of this often repeated, but scientifically unsupported, point of view, see, e.g., Steve Pinker's book The Blank Slate, or any academic research of the type excerpted below.

g on the Job

Although the evidence of genetic and physiological correlates of g argues powerfully for the existence of global intelligence, it has not quelled the critics of intelligence testing. These skeptics argue that even if such a global entity exists, it has no intrinsic functional value and becomes important only to the extent that people treat it as such: for example, by using IQ scores to sort, label and assign students and employees. Such concerns over the proper use of mental tests have prompted a great deal of research in recent decades. This research shows that although IQ tests can indeed be misused, they measure a capability that does in fact affect many kinds of performance and many life outcomes, independent of the tests' interpretations or applications. Moreover, the research shows that intelligence tests measure the capability equally well for all native-born English-speaking groups in the U.S.

If we consider that intelligence manifests itself in everyday life as the ability to deal with complexity, then it is easy to see why it has great functional or practical importance. Children, for example, are regularly exposed to complex tasks once they begin school. Schooling requires above all that students learn, solve problems and think abstractly. That IQ is quite a good predictor of differences in educational achievement is therefore not surprising. When scores on both IQ and standardized achievement tests in different subjects are averaged over several years, the two averages correlate as highly as different IQ tests from the same individual do. High-ability students also master material at many times the rate of their low-ability peers. Many investigations have helped quantify this discrepancy. For example, a 1969 study done for the U.S. Army by the Human Resources Research Office found that enlistees in the bottom fifth of the ability distribution required two to six times as many teaching trials and prompts as did their higher-ability peers to attain minimal proficiency in rifle assembly, monitoring signals, combat plotting and other basic military tasks. Similarly, in school settings the ratio of learning rates between "fast" and "slow" students is typically five to one.

...The existence of biological correlates of intelligence does not necessarily mean that intelligence is dictated by genes. Decades of genetics research have shown, however, that people are born with different hereditary potentials for intelligence and that these genetic endowments are responsible for much of the variation in mental ability among individuals. Last spring an international team of scientists headed by Robert Plomin of the Institute of Psychiatry in London announced the discovery of the first gene linked to intelligence. Of course, genes have their effects only in interaction with environments, partly by enhancing an individual's exposure or sensitivity to formative experiences. Differences in general intelligence, whether measured as IQ or, more accurately, as g are both genetic and environmental in origin--just as are all other psychological traits and attitudes studied so far, including personality, vocational interests and societal attitudes. This is old news among the experts. The experts have, however, been startled by more recent discoveries.

One is that the heritability of IQ rises with age--that is to say, the extent to which genetics accounts for differences in IQ among individuals increases as people get older. Studies comparing identical and fraternal twins, published in the past decade by a group led by Thomas J. Bouchard, Jr., of the University of Minnesota and other scholars, show that about 40 percent of IQ differences among preschoolers stems from genetic differences but that heritability rises to 60 percent by adolescence and to 80 percent by late adulthood. With age, differences among individuals in their developed intelligence come to mirror more closely their genetic differences. It appears that the effects of environment on intelligence fade rather than grow with time. In hindsight, perhaps this should have come as no surprise. Young children have the circumstances of their lives imposed on them by parents, schools and other agents of society, but as people get older they become more independent and tend to seek out the life niches that are most congenial to their genetic proclivities.

A second big surprise for intelligence experts was the discovery that environments shared by siblings have little to do with IQ. Many people still mistakenly believe that social, psychological and economic differences among families create lasting and marked differences in IQ. Behavioral geneticists refer to such environmental effects as "shared" because they are common to siblings who grow up together. Research has shown that although shared environments do have a modest influence on IQ in childhood, their effects dissipate by adolescence. The IQs of adopted children, for example, lose all resemblance to those of their adoptive family members and become more like the IQs of the biological parents they have never known. Such findings suggest that siblings either do not share influential aspects of the rearing environment or do not experience them in the same way. Much behavioral genetics research currently focuses on the still mysterious processes by which environments make members of a household less alike.


Anonymous said...

What I'd be concerned about would not be IQ as a measure of intelligence, but GRE. Can you cite any studies which establish the g content o the GRE, especially the new GRE?
Apparently, the score you get on your essay, which is supposed to measure analytic ability, correlates near perfectly with length.

Steve Hsu said...

I think the table I linked to fits only on Q+V and ignores the A score.

When I took the GRE years ago the A section was all logic puzzles, with no essay component. There is a mention below the table that in some quarters the GRE is no longer accepted as a proxy for IQ.

I've heard that at least in early days Google was using SAT/GPA as measure of IQ/work-ethic. The SAT does correlate very well with IQ and then they could use your GPA (adjusted by degree program) to figure out whether you were an under or over-achiever relative to your abilities.

I think the hedge fund DE Shaw did this as well, and probably a lot of other clever organizations.

Anonymous said...

One thing that surprised me is that we physicists did so well in verbal, relative to all the other technical fields.

Also, am I correct in assuming these figures include both theorists and experimentalists? And we still beat out the mathematicians?

Not to insult our experimentalist friends, but this suggests that theoretical physicts by themselves would be head and shoulders above the rest.

Steve Hsu said...

There was a time in the glory years when the physics V score was higher than all other disciplines except perhaps philosophy!

Your comment about theorists as a sub-population is correct, but I was too PC to make that point :-)

I have never understood why the math scores are not higher, as I consider math PhDs as smart at theorists (pehaps smarter :-) ...

If you look at the Johns Hopkins gifted programs, which are people at the 1 in 10,000 level in math or verbal ability, you also find in their historical data that the most talented overall (both mathematically and verbally) often went into physics, whereas the people who went into math were more lopsided in ability.

Anonymous said...

On the trip home from the Nobel ceremonies in Stockholm, prize-winning physicist Richard Feynman stopped in Queens, N.Y., and looked up his high-school records. "My grades were not as good as I remembered," he said, "and my I.Q. was 124, considered just above average."

James Gleick. (1992). Genius: The Life and Science of Richard Feynman.

Steve Hsu said...

I don't know about his school records, but Feynman's IQ was way above 124. On the math side, the guy won the Putnam competition as a senior without much preparation, so that makes him off-scale. (Mathematician John Nash was traumatized for life at his inability to get into the top 5 despite a lot of training.) Feynman's verbal score might have been low as a kid, but you can tell from his adult writing (or speaking to him) that he had a large vocabulary and was quite eloquent. He often affected an ungrammatical Long Island-ese, but that was just for show.

Anonymous said...

"Growing up in Far Rockaway on Long Island, Feynman spent his childhood repairing neighbors' radios and reading calculus texts for fun. Later, he gained admission to M.I.T. despite a mediocre high school record--a source of "in your face" satisfaction to the brash physicist who, upon returning home from Nobel ceremonies in Stockholm, looked up his IQ. It was 125. Feynman was ecstatic. "To win a Nobel Prize," he said, "is no big deal, but to win it with an IQ of 125, now that's something."

Carson C. Chow said...

The conventional wisdom isn't so much that IQ is not a measure of intelligence but that it is not genetic. The Flynn effect, which shows that IQ's keep rising each generation, is good evidence that it is not genetic but more likely to be environmental. I don't doubt it is a measure of some form of mental capacity perhaps with more meaning in the hard sciences but correlations between IQ and income is weak.

Steve Hsu said...

Regarding Feynman, I can see how the school test might yield 125. It is very likely that the maximum possible score on the math part was only 130-140 (i.e., the questions are not hard enough to distinguish the 99 from 99.9 percentile). In that case, a 140 on the math portion and an average verbal score might net out to 125. I know from the case of my niece that it is very easy to max out on school administered IQ tests. In her school district it was not possible to score above 99 or 99.5 percentile, even if one got all the questions correct.

Carson, there is some evidence that the Flynn effect has already topped out - that is, the generational rise has stopped. I think the twin study data are pretty convincing, but they only address variations in environment to be found in middle class American families. You might find stronger environmental effects (Flynn effect) if you compared poor 19th century farmers with 6 years of schooling to 20th century urbanites with 12 years of schooling. Since a lot of the Flynn data come from military records, that is exactly the kind of variation in question.

Anonymous said...

Using the sum of quantitative and verbal sections of the GRE test to estimate IQ is a terrible method. This is due to the way the two sections are normed: the mean quant score is 620, the mean verbal score is 470 (reference below).

On the quantitative section, besting 90 percent of test-takers earns a 790/800. On the verbal section, besting 90 percent of test-takers earsn a 640/800. See page 13 of this ETS pdf: http://www.ets.org/Media/Tests/GRE/pdf/994994.pdf

So most graduate students in science should have at least 700s on quantitative (>68% of peers), while I doubt very many humanities students with 700s on verbal (>96% of peers) would be at University of Oregon.

-Tim M.

Steve Hsu said...


Good point about the methodology used in the table. English/lit types probably come out a bit lower than they should.

On the other hand, since it is so easy to get an 800 on the Q and A sections, the test can't differentiate between really good science people. This is related to how Feynman might have scored a 125 on his IQ test as a kid.

I doubt the humanists here would appreciate your crack about Oregon, but it doesn't bother me...

Anonymous said...

Of course IQ is partly genetic and partly environmental.

The problem comes with statements like "IQ is 70% genetic". The problem is that this posits IQ as an additive function of a genetic effect and an environmental effect. Clearly, this is false; it must be nonlinear (in statistics-speak, there must be an interaction term).

IIRC, you can come up with models of IQ in which the main effect of genes is very small, yet the heritability (as shown by twin studies) is very large:


Anonymous said...

Imagination is more important than knowledge.

Anonymous said...

Give me a break, stop masturbating your egos. What kind of professor has a childish blog anyways.

Anonymous said...

why waste your talent on this kind of garbage things? please read some literature on IQ from other areas. then you may see my point.

butt said...

Thanks for the information about the averages in the verbal section. Im not very good at this test at all and I believe it is not a very accurate measure of intelligence. Also it definitely does not predict success in school, nor does the SAT. I got a 910 on my SAT and my college GPA was a 3.6 As for the GRE, my highest verbal score was a crummy 450. My quantitative score was not much higher. Changing the format of this test is a decent idea. However, the changes documented on the ETS site are NOT very encouraging. Those people are also impossible to deal with. If you have a question that needs an answer don't bother to call ETS or email them. You won't get a reasonable answer. In short, I still believe that EVERYBODY still places way too much emphasis on standardized tests (especially the GRE) rather than previous academic success.

Anonymous said...

The table is a bit suspect. Medical school applicants DO NOT take the GRE. They take the MCAT, which is far more challenging than the general GRE. Therefore the average IQ they have for Medicine is inaccurate.

chevo said...

I think Tim made most the the points I wanted to express. I would just like to add that according to my calculations using ETS's stats and deviational scores (rather than the scaled scores), Physics majors are #1 but philosophy majors are next in line. 3rd are math majors.

I took into account all three sections V, Q, and A from previous ETS stats when they had analytic section.

On the new GRE with the analytical writing section, phil majors come in number 1 for combined deviational scores in the overall rankings. Admitedly, this sections gives them an unfair advantage. From the V and the Q alone, phil majors are stil 2nd behind physics majors.

Steve Hsu said...


Thanks for posting your results.

But I still don't think we can ignore that so many physics applicants max out on the quant section. I can list 3 groups of applicants for whom the *modal* score is 800; the GRE is unable to measure their mathematical abilities: (1) applicants from China (see link below) (2) applicants of all sorts who are admitted to top departments (3) applicants who will be theoretical physicists. For these people, a conversion from GRE to IQ or "intelligence" is missing out on the most exceptional component of their abilities.

Groups with the strongest mathematical abilities will tend to be underestimated by the GRE simply because they max out. I don't think there is a corresponding population of, e.g., philosophy or comp lit applicants, for whom the modal V score is 800.


Anonymous said...

I don't doubt that physicists are exceptional at these types of tests. I just think that certain rankings disadvantage liberal arts majors on the GRE. (I am a phil major)

Also, I think that because physics departments are heavily international, there might be a "cream-of-the-crop" effect (especially on the Q portion) not seen with non-science disciplines since these other disciplines see a more domestic and representative accross-the-board testing base.

As for the correlation with IQ tests, it would be very interesting to see which profession had the highest average IQ. I suspect that these IQ tests are very similar in what they measure to the GRE test (or SAT).


Anonymous said...

You should be concerned about the whole distribution of IQ, not just the mean. What if it has a low variance? Basically, for the really hard problems you need some outliers. I suspect math gets more of these than physics. And if the CERN experiment shows nothing this fall, expect the mean to drop precipitously in the coming years .... This would be a good thing. I think we need the brightest in other areas like biological sciences and medicine at the moment, unless you see warp drive on the horizon!

Anonymous said...

Physics grad school students may have high GREs because high scorers are more likely to be admitted; do high GRE scores correlate strongly with success as a scientist? I don't have an answer to this.

There's a high (what is high?) correlation between IQ and [fill in the blank]. Since stuff in the brackets is normally thought of as requiring cognition, we say that IQ measures intelligence. This is imprecise since intelligence has not been defined -- unless you are defining it as the thing that IQ measures.

There must be a positive correlation between IQ and how you ultimately do in science. It would be mind boggling if there wasn't. However, the stuff you do on an IQ test is much simpler then the stuff you find in modern physics (or M-physics). Can we measure your ability to do something that is hard by testing your ability to do something that is (relatively) easy? I think this is probably the reason many scientists in grad school won't end up contributing much to our body of knowledge. I think there might be some aspect of cognitive ability (definitions, I know, are vague) that IQ does not measure; if so, it may not always be accurate to say that IQ measures intelligence. Like newtonian mechanics it may not always be a valid measure (i.e. it might correlate highly with your ability to become a doctor, but when it comes to predicting your ability to do cutting edge research in physics, IQ may cease to be valid as a predictor).

Anyway, just food for thought.

Anonymous said...


My personal favourite IQ related bull.

Anonymous said...

i'm pretty sure you can find a complete chart of the average gre scores by intended feild of graduate study on the ets website.

normally i would say that you gre/sat/iq scores would not really predict your success in graduate study, but physics is certainly suited to s type brains, who typically do well on these sort of tests. but of course it all depends on your motivation level, hard-working people obviously always do much better than their lazy counterparts. however studies have shown that you can improve your iq through study, and people who go on to post-secondary education often raise their iq's in comparison to those with similar iq's who did not attend college.

Anonymous said...

Insomniac recent physics graduate...waiting to teach an 8:00am lab....
Interesting discussion. Im a blonde woman, physically the opposite of the steriotype nerd....sound like a high strung ditz....until u listen closley....Tee- hee ..like ..I mean F =q(V X B)..
I can say that no one who was anything less than bright survived...Junior year classical dynamics of systems and particles...cut the last few . I ripped hair out.
More so than I.Q . or whatever....there is some common m undefinable trait among us. It is ADHD like, even/ especially the professors. We are all wierd, in different ways...and make noises at each other...and spazz out...? The coffee? I know I am going to be lonely in the non-nerd world....

Fred Ross said...

I suspect it's also a question of mental machinery. I did physics and math (trained under a Landau school theorist), then completely randomly and accidentally dropped straight into the middle of microbiology. After three years there I think the real difference is tool building.

A physicist is outfitted with incredible tools for cutting up problems, and given some instruction on how to build new ones. Mathematicians have even better tools available but don't learn to use them, just build them.

Biologists (at least at the graduate level) have every bit as much raw potential as the physicists, but they don't have tools that are in anyway comparable. It's like comparing someone trying to move a mountain with a shovel to someone trying to move it with a backhoe.

And by the time you get to college, the physics students probably already have more mental technology than anyone else, so it's biased from the beginning.

Anonymous said...

GRE scores aren't the greatest indicator because they are more dependent upon preparation than are IQ tests, and I would guess that the best measurement of g wouldn't have any reliance on prep. My own personal story, my standardized test scores are always lower than one would predict based upon my iq because I was never willing to spend more than a few hours prepping for the thing.

Anonymous said...

I am a math grad, and this is what I have to say about your post:

I hope for your own sake that you were not being serious about comparing the GRE scores of different majors by simply adding the verbal and the quantitative scores...Even if you corrected for the fact that they are scaled differently (something I obviously don't even need to mention), the verbal score has a much higher correlation with traditional IQ tests than the quantitative part.

Feynman's IQ was 124. He was tested using the Stanford Binet in highschool. He also commented himself that his grades were lower than he had assumed at that time. There have been no studies investigating the correlation between IQ and performance on the Putnam test. Assuming that his IQ is in the genius range because he did well on it obviously implies you know something the rest of the world doesn't.

Lastly, I saw that you tried to challenge his IQ test results by considering the test makeup. The Stanford Binet is known to have a very high ceiling, in fact it has the highest ceiling of all the mainstream IQ tests. Also, it seems rather inconsistent to challenge his results on the basis that the mathematical part of the test probably had too low a ceiling, implying that the mental faculties manifesting in his IQ score were very high in the mathematical area but not so high in the others, accounting for the low score, and then posting an article by Pinker where he basically says "if you have one, you have 'em all". So, either there is something called "g", which makes you overall smart, making Feynman just above average, or the brain is capable of tuning itself to different stimuli, making Feynman misrepresented by that IQ test, and (largely) invalidating the "g" concept.

commentatorator said...
This comment has been removed by the author.
commentatorator said...
This comment has been removed by the author.
commentatorator said...

"GRE scores aren't the greatest indicator because they are more dependent upon preparation than are IQ tests, and I would guess that the best measurement of g wouldn't have any reliance on prep. My own personal story, my standardized test scores are always lower than one would predict based upon my iq because I was never willing to spend more than a few hours prepping for the thing."

The people who make these tests study how preparation affects scores extensively. The keep finding that after the testee understands the instructions to the GRE and acquires some basic math knowledge, extra prep affects almost no increase in scores (about 10-20 points on average). I took the GRE after 2 hours of prep and did very well, as I do on all standardized tests-- big surprise.

By the way: the MCAT isn't harder, but prep does actually make a difference in your MCAT score. Nevertheless, I took it without prep as a sophomore in college and already got an above average score.
You probably took an IQ test as a child to get into a gifted program. But those test scores are notoriously unreliable because everyone develops intellectually at a different rate. Einstein was a late talker, for instance.

If you have a high IQ, you'd probably know it. Your story might go like this: You've taken classical dynamics, electrodynamics, all those courses and had gotten A-'s or higher in all of them, but then, for a challenge, you decided to take senior level math classes and chemistry classes at the same time. You do 21-credit hour semesters just so you can learn more in 4 years while paying the same tuition. And you've had to put less effort into these classes than most of your peers. Your dad won a Fulbright scholarship to study at MIT. Your siblings were valedictorians/saludictorians of their respective high school classes and are going to the best colleges in the nation, graduating with honors, and in 4 years or less. Everyone in your family has a post-graduate degree and most of them are engineers, lawyers, or medical doctors... or, if members of your family weren't lucky enough to be able to attend college, you'd probably find out you have a high IQ when you just happen to score very high on standardized tests without prepping for them.

But your IQ doesn't matter anyway. If I did great things in my life and tested low on an IQ test, I would have the exact same attitude as Feynman.

commentatorator said...

What I should have said is that your IQ only matters to the extent that it predicts what will achieve: If you achieve great things, your IQ score becomes completely irrelevant.

commentatorator said...

This paper is from the 80's, but I don't think they changed the test much (except for removing the analytical section): See "Effects of Coaching on GRE Aptitude Test Scores" by DE Powers.

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Computer said...

I have never seen any question in an IQ-test that in any sense reflects intelligence. Answering
those questions reveals nothing about your intelligence in real life. The fact that only a few succeed ranking high in an IQ test doesn't imply they are the most clever - they could equally well be the most stupid.

Okletsplaytoday said...

How would you explain the some of the most very brilliant (with the highest GRE scores) are weeded out of graduate school,

while the mediocre are left to become professors?

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Uxma Javed said...

Steve studies show that philosophers have the highest iqz :) and I have taken some advanced logic classes where basically the student is applying math precepts to the strange abstract world of ideologies, behavior and ethical outcomes :) that said there is a philosopher in every physicist :) and a marvelous philosopher in a brilliant physicist. From my own life I have seen that physicists can be good at anything because physics is the study of how things work and well that is pretty much (pretty much not absolutely) EVERYTHING there is. 

Uxma Javed said...

Physics guys make a living out of developing schematics for problems OF COURSE they are good at explaining them so they would grasp verbal concepts just as well (this ability to grasp or explain ideas using words is what is tested in the verbal sections of most aptitude tests) ... one thing which ppl tend to forget is that the left brain is involved in verbal AND mathematical reasoning ... now the TYPE of ideas expressed using the language that is what differentiates the physicist from the poet or artist

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