IQ & academic success

This is a revision of a post from my old blog, substantially updated and expanded.

According to a recent meta-analysis, the correlation between IQ and school grades in the general population is nearly 0.55. Meanwhile the correlation between IQ and years of education in the U.S. is also 0.55.  Given the similarity between these two correlations, we can think of them both as just the 0.55 correlation between IQ and academic success.

So in a typical elementary school class (where you have the full range of cognitive ability, including dull students who will drop out later), you might have 30 students, which means that the lowest IQ in the class should be 28 points below average and the brightest in the class should be 28 points above average (IQ 72 and 128 respectively). However because IQ and academic success “only” correlates 0.55, the best and worst students in the class should have IQs only 55% as extreme: 85 and 115 respectively (U.S. norms).

Of course, elementary school grades are only one way we can quantify academic success in the general population. Another way, as mentioned above, is years of schooling or highest degree obtained.

High school dropouts: IQ 85 (U.S. white norms)

In 2006, roughly 17% of American adults, aged 25+ lacked a high school diploma or equivalent.  That means that the median high school dropout was in the bottom 8.5% of education.  If you’re in the bottom 8.5% of IQ, you’d have an IQ of 80 (U.S. norms), or 20 points below the U.S. mean of 100.  But since the correlation between IQ and education is only 0.55, we’d expect high school dropouts to be only 55% as far below the mean, thus have an average IQ of 0.55(-20) + 100 = 89 (U.S. norms)

According to a source provided to me by commenter C, the actual average IQ of Americans with only a 9th to 11th grade education (age 20-90) tested in the WAIS-IV 2006 norming was just as expected: 88.77 (U.S. norms); 85 (U.S. white norms)

University grads: IQ 108 (U.S. white norms)

By 2006, roughly 26% of American adults, aged 25+ had a bachelor’s degree or more.  That means that the median university graduate, is in the top 13% of education.  If you’re in the top 13% of IQ, you’d have an IQ of 117 (U.S. norms), in other words, 17 points above the U.S. mean of 100.  But since the correlation between IQ and education is only 0.55, the expected IQ of university grads would be 0.55(17) + 100 = 109 (U.S. norms).

How close does this prediction come to the actual data?   The actual IQ of U.S. university grads (age 20-90) tested in the WAIS-IV 2006 norming  was 110.77 (U.S. norms); 108 (U.S. white norms).

PhDs: IQ 119 (U.S. white norms)

In the U.S., a PhD roughly marks the top 1% in years of completed education, which suggests that the median PhD is in the top 0.5% in education level. If there were a perfect correlation between IQ and academic success, we’d expect the average PhD to have an IQ of 138 (the top 0.5%), but since the correlation is “only” 0.55, each point above 100 must be multiplied by 0.55, reducing the expected average IQ of PhDs to about 121(U.S. norms); 119 (U.S. white norms).

The only actual recent data on the IQs of U.S. PhDs that I’m aware of comes from Charles Murray’s book Coming Apart, which reported that for PhDs turning 25-29 in 2005-2009, the average IQ is 124 (U.S. norms).  However this is probably too high because (1) Murray’s sample was limited to white PhDs, and (2) the test used was the AFQT, which is arguably an achievement test, not a conventional IQ test, and thus might over-correlate with education.  The true average IQ of PhDs is probably several points lower, just as simple regression would predict.

Harvard students: IQ 125 (U.S. white norms)

Are there academic achievements more impressive than getting a PhD? Yes. Getting acceptance into Harvard: the world’s most prestigious university. Out of the 4.1 million 18-year-olds in the U.S. in a given year, only about 1600 go to Harvard. So if there were a perfect correlation between IQ and academic success, the dumbest Harvard student would have an IQ of 150 and the median might have an IQ of 153. However because the correlation is only 0.55, the median Harvard student should be only 55% as far above 100. Thus, simple regression predicts the typical Harvard student should have an IQ of 129 (U.S. norms).

Actually a sample of Harvard students studied by Harvard psychologist Shelley Carson and her colleagues clocked in at IQ 122 (U.S. norms); 120 (U.S. white norms) on an abbreviated version of the Wechsler intelligence scale.  On the other hand, Harvard undergrads are rumoured to average 166 on the LSAT, which equates to an IQ of about 132 (U.S. norms).  The abbreviated Wechsler estimate is perhaps too low because of ceiling bumping, poor sampling, and an over-emphasis on spatial ability, but the LSAT score may be too high because it’s too much of an achievement test.  Averaging them both gives an IQ of 127 (U.S. norms); 125 (U.S. white norms). Very similar to the predicted level.

I completely ignored the stratospheric SAT scores of Harvard undergrads because being selected by this test, it’s an outlier on which they score high by definition.

Tenured professors: IQ 127 (U.S. white norms)

Another form of academic accomplishment that’s about as exclusive as attending Harvard is becoming a tenured university professor. Scientist Steve Hsu wrote:

…when an attorney prepares a case it is for her client. When a Google engineer develops a new algorithm, it is for Google — for money. Fewer than one in a thousand individuals in our society has the privilege, the freedom, to pursue their own ideas and creations. The vast majority of such people are at research universities. A smaller number are at think tanks or national labs, but most are professors…

So in terms of academic success, being a full tenured professor is a one in thousand level accomplishment. If there were a perfect correlation between IQ and academic success, the dumbest tenured professor would have an IQ of 147, and the average tenured professor would probably be around 150. But since the correlation is 0.55, we should expect the average tenured professor to be around 128 (U.S. norms); 127 (U.S. white norms) with quite a bit of variability around that mean, depending partly on the prestige of the university they teach at and the g loading of the subjects they teach.

Academic Nobel Prize winners: IQ 148 (U.S. white norms)

Are there academic accomplishments more impressive than becoming a professor or going to Harvard? Yes: Winning the Nobel Prize. Many years ago a respected psychometric expert named Garth Zietsman wrote an article about using this type of regression to estimate the IQs of Nobel laureates, though I don’t remember the exact stats he used.

But let’s say only one in a million American adults has a Nobel prize (excluding the Nobel peace prize which is non-academic). If there were a perfect correlation between IQ and academic success, we’d expect the dumbest American Nobel laureate to have an IQ of 171 and the average Nobel laureate to be around 174. But again, since the correlation is 0.55, the average Nobel laureate should have an IQ of 141 (U.S. norms); 140 (U.S. white norms).

The only data on the actual IQs of Nobel level scientists is probably outdated.  In the Roe study, the average IQ of eminent scientists was 166 on a verbal test (the best proxy for IQ in the study).  On the other hand, in the Terman gifted study, the IQ of the two kids who would grow up to win a Nobel Prize was 129 (too low for the study).  The Roe study average was probably too high because of the academic nature of the test, and because the sloppy way the test was normed, while the Terman study suffered from too small a sample of Nobel Prize winners perhaps tested at too young an age.  Averaging both studies together gives IQ 148 as the best estimate for academic Nobel Prize winners.  This is higher than predicted by simple regression from IQ and academic success, perhaps because the data is outdated, or perhaps because at the highest levels, academic achievement becomes more creative, thus increasing the correlation.


Is it already possible to take a biological IQ test?

I often define intelligence as the cognitive ability to adapt, but in neurologists speak of neural adaptability, which has a more scientific definition.  Neural adaptability is measured by hooking your head up to an EEG monitor and calculating the ratio of brain amplitudes evoked from having you hear a clicking sound at random intervals, to the brain amplitudes evoked from having you hear a clicking sound when ever you press a device.

The higher the ratio, the higher the IQ on average.  This is because more adaptable brains conserve energy by not wasting brain activity on what they already expect.

On page 155 of The g Factor, Arthur Jensen suggests that in the general U.S. population, neural adaptability may correlate as high as 0.8 with IQ, which is about as high as two well respected IQ tests correlate with each other.

It seems IQ really is a biological construct and not a cultural one.

Does Italy have the highest IQ and brain size in Europe?


The large brain size of Italian American James Gandolfini may have partly caused his great acting talent. (PHOTO:

In his 2006 book Race Differences in Intelligence, Richard Lynn listed the brain sizes of many different populations (originally published by Smith and Beals, 1990) and to my surprise, the brains of Italians clocked in at 1411 cm3, higher than any other European group in the dataset.  1411 cm3 might not sound that extraordinary, but keep in mind that these figures are probably based on very old skulls because (1) you have to be dead before someone can fill your cranium with lead shot or beads and thus directly measure its volume, and (2) craniometry has been taboo since WWII.

Because Westerners before WWII were 1.3 standard deviations stunted in height (sub-optimum nutrition and disease associated with the rise of agriculture), and probably also in brain size, I would estimate that the cranial capacity in today’s Italy is an incredible 1529 cm3.

Of course it’s possible that some other European countries have caught up with or surpassed current Italian brain size (especially the well nourished and healthy Dutch, who have enjoyed an incredible 20th century growth spurt), but I suspect Italians are still the biggest brained for their body size (most encephalized).

Well, I didn’t think much of it.  Data on subpopulations is often unreliable because of smaller sample sizes and looking for HBD trends within a continent as homogenous as Europe seemed to be cutting the data too thin.  But then I looked at Lynn’s listing of national IQs.  These figures are notoriously unreliable, often based on small unrepresentative samples, and even Lynn admits they’re extremely rough, but uses them only to look for larger continent level trends.

Nonetheless, on a scale where whites in America, Britain and Australia average 100, Italy clocked in at 102, making them the “smartest” country in Europe, or anywhere else outside of East Asia.

Both the biggest brains in Europe and the highest IQ in Europe?  That’s probably not sampling error I thought, and the strong match between brain size and IQ is great news for HBD, as is the fact that both are paralleled by the incredible accomplishments of ancient Rome.

But the big brains and high IQ of Italians is also bad news for HBD because for a long time, HBDers falsely believed Italians to be genetically inferior (a stereotype the pretend to be liberal media continues to push with shows like Jersey Shore).

When they first arrived in large numbers in the United States,  the tall, thin, pale WASP elite felt the newcomers looked primitive.  They were disgusted by their darker more hirsute complexions, and were appalled by their shorter and more muscular physiques.  Making matters worse, the for the first 50 years of the 20th century, Italian Americans confirmed these stereotypes by scoring further below the WASP mean on IQ tests than today’s Jewish Americans score above it.  From Stephen J Cici’s book called On Intelligence…More or Less


Boxing ability & height correlation

I saw some fascinating research in the book Anthropometrica: A Textbook of Body Measurement for Sports and Health Courses showing that heavyweight boxing champions tend to be two standard deviations taller than the average American man of his era.


This is fascinating because I have long estimated that U.S. presidents are about two standard deviations smarter than Americans of their era (IQ 130).

What this suggests is that physical power is to height, as REAL power is to IQ.

The World heavyweight champion is the most physically powerful man in the sense that he can destroy virtually anyone physically in the unlikely event it ever came down to one on one unarmed physical combat, but the president is the most powerful man in a real sense, in that he can destroy virtually anyone politically, economically, or militarily in scenarios that are likely to actually occur.

Of course not all heavyweight boxing champions have been tall, just as not all U.S. presidents, have been smart.  And some heavyweight boxing champions have been absolute giants, just as some U.S. presidents have had IQs above 150 (Jefferson?).

But on average, World heavyweight boxing champions are just as selected for height as U.S. presidents are selected for IQ: + 2 SD, which equals about 6’3″ on the U.S. height scale, and 130 on the U.S. IQ scale.

This suggests that the correlation between height and physical power, is similar to the correlation between IQ and real power: About 0.4

The IQ scale is messed up

Some of my commenters seem to think the IQ scale is like percentage.  That is if you have 90% as many neurons as the average person, your IQ is 90.  Nothing could be further from the truth.


The IQ scale was originally based on the idea that if a child was mentally functioning at 50% of his chronological age, he had an IQ of 50, and if he was functioning at 150% of his chronological age, he had an IQ of 150.

So an adult (age 16 to 19), who would score like an eight-year old, would have an IQ around 50.  The problem with this is that as the above chart shows, an eight-year-old does not have 50% of the brains of an adult, but more like 95%.  I realize there’s much, much more to intelligence than just overall brain size, but assuming the brain size growth curve is typical of the growth of other brain properties, the IQ scale is wildly distorted, in that it makes the moderately retarded mind seem only half as developed as the average mind, when in reality, it’s more like 95% as developed as the average mind.

If the IQ scale were based on the actual linear growth of absolute neurological development, instead of having a mean of 100 and a standard deviation of 15, it would have a mean of 100 and an SD of maybe 1.7.

This explains why I was having so much trouble mapping chimps to the human IQ scale.  Chimps are about as smart as human toddlers, and as the above chart shows, the neurological development during the toddler years is far greater than in childhood and adolescence combined, but because the concept of IQ is based on linear mental age units, these huge low level differences get compressed, while differences above the human toddler level get extremely exaggerated.

The ideal IQ scale

When Alfred Binet invented the first intelligence test circa 1904, he needed a unit of measurement.  After all, a stadiometer has inches; a spring scale has pounds; but what could be the unit of measurement for a trait as abstract as intelligence?

He decided on mental age.  That is, if you performed as well on his test as an average white six-year old, you have a mental age of six, regardless of what your chronological age.  If you performed as well as an average white ten-year-old, you had a mental age of ten etc.

Sometime later, psychologist William Stern suggest one take the ratio of the mental age to the chronological age, and then multiply by hundred to remove the decimal point, and the concept of IQ was born.

But from the beginning, there were problems with the IQ.  For one thing, intelligence only increases as a function of age up until about 16 or so, and as we get much older our intelligence declines.

Secondly, even in childhood, the increase in intelligence as a function of age is not always linear.

Third, the scale lacked a true zero point.  Someone who had the test score of a newborn baby would have a mental age of zero, but a baby does not have zero intelligence.  It’s brain has been developing in the womb for 9 months prior to birth.

Today we no longer calculate IQs the way William Stern suggested, but we still make sure the average is around 100 and the standard deviation is around 15 or 16, since those were the stats the old age ratio scales yielded.  But I long for the IQ scales of old, because despite their many flaws, at least they represented something tangible.

To once again anchor IQ tests in something tangible, I propose scores be converted not into mental age, as Binet proposed, but mental brain size.  If you perform as well as the average white young  adult male with a brain volume of 1400 cc, you have a mental brain volume of 1400, regardless of your actual brain volume.  If you perform as well as the average  white young adult male with a 1500 cc brain volume, you have a mental brain volume of 1500 etc.

This would anchor IQ scores in concrete physical reality and would be a true ratio scale with a true zero point.

Update, January 8, 2017:

Allow me to clarify the above post with an analogy:

Suppose we had a scale to measure weight, but it could not give us a meaningful number, it could only tell us that person A weighed more than person B.  We didn’t know if person A was 500% heavier than B or just 1% heavier than B, all we knew was that he was heavier than B.  All the scale could do was rank people.

Well, one was could make the weight scale more useful is we noticed that taller people weigh more than shorter people on average (lots of exceptions).  We could then assign each person who stepped on the weight scale, a height, and say person A has the weight of an average 70 cm man, while person B has the weight of an average 60 cm man.  Assuming the correlation between height and weight is linear, this would allow us to say person A is 17% heavier than person B, something we could not say when we only had a rank.

Of course this would not imply that height is the only cause of weight, or even causal at all; nor would it imply height and weight are strongly correlated.  What it would do is provide a concrete easy to understand true ratio scale with a real zero point to which weight could be anchored

Currently IQ tests can tell us who scored higher than who, but they can’t tell us by what percentage person A exceeds person B on the actual ability in question, so the purpose of this post was merely to suggest they too need to be anchored in a concrete scale with a true zero point, and brain size is one such anchor out of many that might be used.


Obama thinks he’s very, very, very smart

I was watching Charlie Rose tonight and he was interviewing Jeffrey Goldberg of The Atlantic who won widespread praise for his article The Obama Doctrine.  It’s amazing how much access Obama gave to this reporter and I suspect it’s because Obama was nervous that his tumultuous relationship with Bibi Netanyahu was alienating the Jewish community, so he bends over backwards to be nice to Jewish journalists.

During the interview Goldberg said that Obama has very little patience for people who are not as smart as him, and while Goldberg concedes that Obama’s very, very smart, he thinks Obama considers himself to be very, very, very smart.

Since an IQ of 100 is average intelligence, I think an IQ of 110 makes you smart, and an IQ of 120 makes you very smart.  Thus it follows that an IQ of 130 makes you very, very smart, while an IQ of 140 makes you very, very, very smart.  So if both men were familiar with the IQ scale, Goldberg might rate Obama 130, while Obama would rate Obama 140.

Yesterday Rose had on Presidential historian Doris Kearns Goodwin who talked about her relationship with Obama.  Even before Obama was president, he wanted to meet Goodwin to talk about her book Team of Rivals, to understand how Lincoln could have staffed his cabinet with former adversaries.  The book is credited with causing Obama to choose his former rival Hillary Clinton to be Secretary of State.

While Goodwin could see Obama becoming a full-time writer and intellectual, she was more analytical about his intelligence than others.  She said writers often write huge books because they can’t say things simply and for all of Obama’s skills as a communicator, she felt he couldn’t master the most important one of all:  How to talk in sound bites in our fast paced media age.  That takes a different kind of thinking, Goodwin explained.

I’ve sometimes thought verbal IQ could be divided into two sub-categories: writing IQ vs talking IQ.  Obama delivered brilliantly written speeches but his real time debate performances against rivals as diverse Alan Keyes, Hillary Clinton, and Mitt Romney, were often panned.

Neanderthal IQ, behavioral modernity & brain shrinkage

I now believe Neanderthals had an IQ of at least 85, not 70 as I had estimated earlier.

Why at least 85?

According to this article, until about 50,000 years ago, Neanderthals were more technologically advanced than AMH (Anatomically Modern Humans).

This suggests their IQs were higher than the AMH who lived before the upper Paleolithic.

Before the upper Paleolithic, I suspect all AMH resembled Bushmen, pygmies, and Australian Aboriginals, and I would guess these have a genetic IQ of 80, so Neanderthals were likely at least 85 to have had better tools

But why did Neanderthals suddenly fall so far behind?

It seems the shape or position of their larynx prevented fully modern speech so they never acquired the advanced language that AMH enjoyed.

This also may explain why AMH was also so primitive before 50,000 years ago, yet suddenly so advanced after 50,000 years ago, despite no noticeable change in brain size. Perhaps prior to around 50,000 years ago, the AMH larynx resembled that of Neanderthal’s in its form or position.

Perhaps scholar Richard G Klein was right about a genetic mutation causing behavioral modernity, but instead of a mutation in the brain, as Klein argues, it was a mutation in the neck.  This mutation produced fully modern speech allowing us to pool our huge brains and share ideas, creating a collective intelligence that was far smarter than any one individual.

It would also explain why Neanderthals stayed so primitive, despite having such big brains. It may even explain why shortly after the Upper Paleolithic Revolution, brains suddenly started shrinking after millions of years of explosive growth.  Advanced language and the huge cultural knowledge it had produced, had made individual genius redundant, and huge metabolically expensive brains, a pointless and expensive liability.

Seldom has one theory so parsimoniously explained so many mysteries.

In order to test my hypothesis, we would need to see neck bones from AMH prior to the Upper Paleolithic Revolution, to see if they resemble Neanderthal’s.

For more on this, start watching at 6:48 in the below video

And at 3:30 of next video:



The IQ of dolphins


Commenter MeLo asked about the IQs of dolphins.  According to Wikipedia, the tucuxi dolphin have an encephalization quotient of 4.56, meaning their brains are 4.56 times bigger than the statistically expected brain size for an animal their size (not to be confused with simple brain size/body size ratio which is a less accurate measure of intelligence).

The EQ of dolphins is larger than that of chimps (2.4) and they have IQs around 35, but smaller than that of Homo erectus (6.0), who likely had an IQ around 55.  This suggests an IQ around 45.

To put these numbers in perspective, modern humans have an EQ of 7.61 (far and away the highest in the history of the World, if not the galaxy, and in some countries, our average IQ exceeds 100).

But the fact than IQ as high as perhaps 45 could have evolved independently in a lineage so divergent from humans is strong evidence that evolution is progressive and that intelligence is the ultimate adaptation: an ability to adapt itself.

And indeed, few animals have had to adapt as much cetaceans whose ancestors first adapted to the oceans, then evolved into successful land animals, only to have readapt to ocean life.  Few organisms have travelled such a transformative evolutionary path, making dolphins especially evolved, adaptable and intelligent.

Because evolution is so incredibly progressive, I predict that if humans go extinct, and the earth remains intact, within 10 million years there will be another species, at least as intelligent as we are.  It seems dolphins have already made it up to IQ 45 and chimps and even crows are not far behind; it’s only a matter of time before one of their descendants hit 100.

Because evolution is progressive and intelligence is perhaps the ultimate adaptation.


HBD is making more sense now

A while ago I took IQ and brain size data mostly reported by Richard Lynn and attempted to correct it to show the IQs and brain sizes the races would have if they all enjoyed First World 21st century living standards.  I called these corrected values, genetic IQ and genetic brain size, though in fairness, many actual anthropologists would call it pseudoscience.

race iq real iq (rounded) genetic iq (rounded) brain size genetic brain size
ashkenazim 108 110  110 1457
east asians 105 105  105  1416  1534
whites 99 100  100 1369  1487
arctic people 91  95  95  1443  1561
southeast asians 87  90  95  1332  1450
native americans 86 90  90  1366  1484
pacific islanders 85 90  90 1317  1435
dark caucasoids 84 85  90  1293  1411
congoids 67  75  85  1280  1398
australoids 62 65  70  1225  1343
capoids 54 60  70 1270  1388
pygmies 54 60  70 1085  1203

The problem was that the IQs Lynn reported for Bushmen, Pygmies and Australoids were so incredibly low (even after correcting for their low human development index) that I was left with a very steep slope for predicting a population’s genetic IQ from its genetic  brain size.  The absurdity of this steep slope became apparent when I tried to extrapolate the trend beyond humans and predict the IQ of chimps from their cranial capacity (about 498 cc if adjusted for their small size), and got an estimated IQ below zero!


I decided that the problem was that Lynn’s IQ data for Australoids, Bushmen and pygmies simply isn’t credible.  You can’t give conventional IQ tests to people still living in hunter-gatherer societies and expect to get good results and there’s no credible evidence that any extant human race or ethnicity has a genetic IQ below the 80s. So after removing these three outliers, we get the following line of best fit predicting population IQ from population brain size.


Now when we predict the IQs of chimps from their cranial capacity we get 26, which is within 10 points of actual laboratory research suggesting an IQ of 35.