Out of all the negative correlates of IQ, my favorite is weight/height ratio. By negative correlation, I mean that the two variables tend to move in opposite directions, so the higher one’s weight/height ratio, the lower one’s IQ tends to be. Why is this my favorite negative correlation? Because it confirms all the stereotypes we see in movies about the skinny nerd being smarter than the beefy jock, and the completely anorexic space alien invader being way smarter than both. It’s also consistent with our evolutionary history. As humans evolved from dumb apes, we gained height and lost muscle. As scientist Steve Hsu once quipped, “we are the geeks of the animal kingdom” and you can kind of look at the way humans slaughtered the burly neanderthals and are now racing to destroy the planet for all the musclebound animals as a kind of inter-species version of Revenge of the Nerds or what the Lion of the Blogosphere calls beta male rage.
But within humans, how real is this negative correlation between IQ and weight/height ratio, what’s causing it, and how strong is it? Blogger Jayman seems to feel the negative correlation is driven by low IQ fat people, rather than the dumb jocks. Jayman writes:
It is commonly known that poorer (i.e., stupider) people tend to be fatter. It is commonly believed that this stems from things associated with low IQ, like poor impulse control and low future-time orientation, and indeed those things likely play a role. But it’s telling to see just how stark the relationship is.
Satoshi Kanazawa (who, despite the removal of his Big Think page, still very much publishes; see his website) did just that. Looking at a nationally representative primarily White British sample (n just under 10,000 in the last waves, 97% White), he found that IQ measured in childhood excellently predicts obesity at age 51:
Technical points (you may want to skip this part)
While the chart Jayman cites certainly makes it appear as though there’s a strong relationship, I respectfully disagree with Jayman’s claim that childhood IQ “excellently predicts obesity at age 51”. What the chart shows is that people with childhood IQ’s below 75 (probably IQ 70 on average) and people above childhood IQ 125 (IQ 130 on average) differ by 2.9 BMI units. Based on using the standard errors and sample sizes reported this source, I was able to calculate that American white men and women in their 50s both have a mean body mass index of 29 and a standard deviation of 7 to 9. While weight is probably lower in Britain, they also probably have a BMI standard deviation around 8. What that means is that people who differ by an astonishing four standard deviations in childhood IQ, differ by only 0.36 standard deviations in BMI. This implies the correlation between childhood IQ and age 50 weight/height ratio is only -0.09. Squaring the correlation, childhood IQ explains less than 1% of the variation in age 50 BMI. Hardly an excellent predictor.
However it may be unrealistic to expect much of a prediction from childhood IQ, since childhood IQ only correlates about 0.7 with adult IQ. Dividing the -0.09 correlation by 0.7 gives -0.13 which probably better reflects the relation between IQ and weight/height ratio. Still a very weak correlation, but a lot more respectable looking.
Anorexic IQ (technical analysis, you may want to skip)
A second way to estimate the negative correlation between IQ and weight/height ratio is to look at the IQ’s of anorexics. According to this meta-analysis, anorexics have IQ’s about 11 points higher than average when measured on the Wechsler scales and 6 points above average when estimated from a reading test. Normally I would split the difference, but a lot of academics are clueless about the Flynn Effect and are probably administering outdated versions of the Wechsler scales that give inflated scores. Since reading tests are much less sensetive to outdated norms, I will assume anorexics are 6 IQ points smarter than average. And since anorexics tend to be overwhelmingly white, and the whites score about 3 IQ points above the national average, anorexics score only 3 points higher than other whites. On the other hand, anorexics are overwhelmingly women, and women score maybe 2 points lower than the national average, and so anorexics are probably roughly 5 points smarter than other white women (+0.33 SD)
How much skinnier than average are anorexics? Well based on this source, white American women under 40 have an average body mass index of 26.5 with a standard deviation of 8.9. Assuming the average anorexic woman is a white woman under 40 with a BMI of 17, then anorexics are 1.07 standard deviations skinnier than normal (for young white women). Given that they are 0.33 SD smarter than normal, this implies a negative correlation of -0.31 between IQ and weight/height ratio.
The Bottom Line
Based on my analysis of the chart Jayman’s cited and my analysis of anorexic IQ, I estimate that among people of the same country, gender, and ethnicity, the negative correlation between IQ and weight/height ratio is -0.13 to -0.31; splitting the difference, about -0.22. This is may be a low correlation, but small correlations can have big effects, and what this correlation really suggests is that among people of the same age, gender, race and nationality, the scrawniest 2% will be a full 13 IQ points smarter (on average) than the least skinny 2%, though virtually the full range of human intelligence can be found at virtually every body type. So before you condescend to the big bury bouncer, just remember, he might be the smartest man in America.
Brain Size 
VIQ has showed an immense adult Flynn effect mostly because of one sub-test: Similarities.
I don’t believe the vocabulary Flynn effect was that large for adults. Maybe in Flynn’s data set, but as you know, the WB and the original Binet both had hard vocab tests and now a recent study just found zero Flynn effect on wordsum.
The correlation (about -0.2) was given in the paper. Could have saved yourself some work. 🙂
Your comparisons between the U.S. and the U.K. are off because you need to control for race. The values given for the U.S. aren’t the White-only values.
Indeed, Brits are just as fat as U.S. Whites (as are all Anglos).
Granted, all these obesity measures would be better if they used body fat %age, but obviously that’s harder to assess.
The correlation (about -0.2) was given in the paper. Could have saved yourself some work. 🙂
Very interesting. I agree it’s roughly -0.2 but going just by that chart I would have guessed lower.
Your comparisons between the U.S. and the U.K. are off because you need to control for race. The values given for the U.S. aren’t the White-only values.
Actually the source I cited had racially segregated data and I was using whites only U.S. stats.
Indeed, Brits are just as fat as U.S. Whites (as are all Anglos).
Granted, all these obesity measures would be better if they used body fat %age, but obviously that’s harder to assess.
What I want to know is what the correlation is between IQ and fat-free body weight
Very interesting. I agree it’s roughly -0.2 but going just by that chart I would have guessed lower.
And actually at the bottom of page 438 of the paper, Kanazawa reports that the correlation between childhood IQ and BMI at 51 is -0.096.
Click to access O2013.pdf
I estimated -0.09 just from the slope of the standardized regression line implied by the chart. Jayman’s right that I could have saved myself a lot of time had I read the entire paper, but it’s great to know my indirect estimate was so accurate.
I respectfully disagree with Jayman’s claim
Why respectfully? Jayman is a moron.
You have nothing against JayMan other than ad hominems and personal attacks. Fuck you.
[user name edited by pumpkinperson, sept 26, 2014]
Gregory Cochran also proves your ideas wrong here.
[user name edited by pumpkinperson, sept 26, 2014]
Again Scott you’re only proving your gay-ness.
The “breeder’s equation” IS applicable to populations with small genetic and small environmental variance.
It IS applicable.
Otherwise it is NOT.
In the modern world especially the breeder’s equation is “quaint”.
Immigration and emigration combined with a rapidly changing technical environment means that selection and evolution are impossible.
I’m trying to make clear that the breeder’s equation is immensely useful in understanding evolution, history, contemporary society, and your own family.
Scott,
Lay off the meth, tattoos, facial hair, piercings, and legible clothing.
Only in ‘mer’ca are the white underclass their own political enemy.
I challenge you to find me at least one negative peer-reviewed review of The 10,000 Year Explosion. Then maybe your statements are something to pay heed to.
[user name edited by pumpkinperson, sept 26, 2014]
Dookie writes:
“Immigration and emigration combined with a rapidly changing technical environment means that selection and evolution are impossible.”
There you have it, ladies and gentlemen. Our brilliant BGI participant is saying the evolution of homo sapiens is over and done with. Finito. Fini. Terminado. Fertig. 完 了.
It has to do with migration and technology. He learned about them in school, you see.
All of my physical traits fit high IQ type except my body shape which is more like a wrestler in category of over-weight.
With mutliple correction factors, you get the picures. Only simple minded people will get confused. These simple people want clear answer since their mental ability is limited to handle simple stuff.
Classical signs of mentally challenged people: strong emotional display (anger, passion, easy excitment)
Mentally challenged people are weak on their neocortex and strong on primitive part of brain which is only brain for reptile. Reptile basically function on their emotions since they do not have any neocortex at all. They judge thing by their guts feeling(emotion). Similarly mentally challenged people display their gut feeling in their language with lots of cursing, insult, like, dislike, love, ect. Bottomline they think with their guts. They basically can not think with cool logical reasoning and abstract logics. But these people never feel they are dumb. They often feel their fellow dump people make sence to them because only dumb judgemnts make sense to them.
so it is no wonder that stupid people share the same conclusion about any thing. The same can be said for intelligent people. Only way to differentiate people apart is through math like test like IQ test. Certainly easy way is to measure their head sizes.
I mean multiple correlation factors for certain trait (especially like polygenic IQ). On my genetic sequencing, I even carry one marker for lower intelligence. All my proffessors are in disbelief since my educational and social achievment controdicting that. But I reminded them that intelligence is polygenic that you really do not need to have all smart genes to be smart.
Classical signs of mentally challenged people: strong emotional display (anger, passion, easy excitment)
I agree that highly intelligent people tend to be good at keeping their calm and cool under pressure. Not always, of course, but as a general rule. Low IQ people by contrast are much more at risk for going ballistic & yelling & screaming hysterically when they become angry.
Mentally challenged people are weak on their neocortex and strong on primitive part of brain which is only brain for reptile. Reptile basically function on their emotions since they do not have any neocortex at all.
I don’t know about this. I think intelligence and emotions evolved together. Intelligence is the ability to problem solve but our emotions determine what is a problem. Emotions are what motivates us to use our intelligence in whatever way it evolved to be used. So we feel an emotion like fear so that we are motivated to use our intelligence to kill the tiger that threatens to eat us. If we were too stupid to figure out how to kill the tiger or even know to run away from it, there’d be no point feeling fear & fear wouldn’t have evolved.
There’d be no point in reptiles feeling emotions because they’re too stupid to solve the problems their emotions would identify. So rather than being emotional creatures, I think reptiles are like mindless zombies that just robotically go through the motions of life with no feeling or awareness; just utter blank nothingness.
Reptiles are not evolved enough to feel pain. Physical pain like emotional only evolved in animals that are smart enough to figure out how avoid them. Otherwise it’s just pointless torture.
I actually think smarter people have a shorter fuse, because they are so smart, they hold high standards and find a lot of things to get angry about that people of normal IQ don;t notice and or don’t care.
grey enlightenment, I think high IQ people get angry, but they tend not to go to hysterical. A friend of mind has an IQ below 70, and she just goes absolutely ballistic. One time at a bar, she had a bit too much to drink and started throwing tables and chairs around, throwing whine bottles at total strangers, screaming hysterically at the top of her lungs for a full half hour, charging strangers and trying to wrestle them to the ground. The bartender had to call the police.
http://mybrainnotes.com/evolution-brain-maclean.html
Emotion brain is evoltionarily primitive compared to neocortex. Neocortex supresses the impulse generated in emotional brain. Low IQ people have weak neocortex, thus they demonstrated strong emotional reaction (lack of inhibition by neocortex).
True scientists are like physicists who associate any phenomena or funciton with identifiable structure. Verbal people just arguing over empty reasoning which leads to nowhere.
How many Jews do you know? Very few, right?
In low income countries poor people are underweight.
Yes, the negative correlation between IQ and weight/height ratio appears to be a first world phenomenon. Wordwide, the correlation is probably positive.
@Pp – On the whole I think the weight – IQ relationship is a red herring. Such weak and confounded (eg by social class and race) relationships don’t really help with understanding intelligence, since they themselves requires such a lot of explaining.
Another aspect is that you seem to be conflating endomorph (fat high BMI people) with mesomorphs (muscular high BMI people).
http://en.wikipedia.org/wiki/Somatotype_and_constitutional_psychology
Impressionistically, I would guess that it the non-confounded inverse relationship would me more likely mesomorphs, than endomorphs – given the number of highly intelligent but more or less obese people (including geniuses) – and the relative scarcity of very highly intelligent ‘jocks’.
Also to be taken into account are Rushton’s between-race measures, in which the relatively fatty Asians come top for intelligence and the relatively muscular Africans come bottom – this is ambiguous in relation to your theory, but implies a need for racial controls.
Given that “virtually the full range of human intelligence can be found at virtually every body type” I don’t think there is very much to be expected from this line of inquiry – but it is fun to think about!
Yes, I agree ideally muscle & fat should be distinguished but I’m aware of no study that bothered to tease them apart. I find it interesting that as humans evolved more intelligence, they became more gracile. In the book “The 10,000 year explosion”, it was suggested that there was a genetic tradeoff between brains & muscle.
Much more gracile and much less sexual dimorphism too.
Humans are quite sexually dimorphic as mammals go but much less so than apes.
@Pp- ” In the book “The 10,000 year explosion”, it was suggested that there was a genetic tradeoff between brains & muscle.”
I think this is true – although I tend to regard it more as ‘athleticism’ than muscle tissue (the muscular aptitudes needed for things like hand to hand fighting, sprinting, jumping).
It may depend on how quickly higher intelligence needed to evolve, how harsh was the selection pressure. Ashkenazim would seem to have been under very harsh selection pressure for higher intelligence, and this led to lower athleticism plus the characteristic genetic diseases. The English were probably under a less harsh and more prolonged selection pressure for higher intelligence, or were just luckier with the mutations, and did not seem to sacrifice so much athleticism.
But, as a general rule, harsh selection pressure leads to genetic problems – there is a trade off. This is most clearly seen in terms of resistance to infectious disease – if almost everybody dies, then the resistance to the disease displaces other fitness considerations – and population is re-founded from what may be a small number of survivors – and along with disease resistance the descendents may inherit various deleterious mutations that just happened to be present in those with disease resistance.
But, as a general rule, harsh selection pressure leads to genetic problems – there is a trade off.
Indeed. Trade offs are the nature of all evolution.
Bruce is clueless as usual.
NE Asians are more muscular than sub-Saharan Africans as a group.
How do I know?
It’s in my World Book Encyclopedia from 1960.
Africans — linear
Mongoloids — muscular
And, obviously, Nordicists have a problem here, because Scandinavians and Finns dominate power lifting and Caucasians generally dominate Olympic weightlifting.
Actually according to the Lion of the Blogosphere, blacks are the most muscular race:
And, obviously, Nordicists have a problem here, because Scandinavians and Finns dominate power lifting and Caucasians generally dominate Olympic weightlifting.
Maybe they’re just more variable? The average Nordic doesn’t seem muscular; only the far right of their bell curve.
Actually Lion is an idiot. He states things as fact which aren’t. It’s called “truthiness” in America.
Slaves may be an exception as they may have been selected for muscularity. And Africans are diverse. The half Kenyan Obama looks pretty “wimpy” to me.
But, in general, the average West African, the most muscular of Africans, is less muscular than the average Mongol or Manchu, I’d bet.
Scandinavians and Siberians/NE Asians may follow Bergmann’s rule. If they also follow Allen’s rule, the their shorter limbs may be an advantage in weightlifting. I don’t know.
But in terms of height, the Dutch and the Icelanders are the world’s tallest and near its most robust. The most robust are the Polynesians.
I don’t think African-Americans are muscular because slaves were selected for muscularity, I think West Africans just have a lot of muscular genes & they’re more evident in America where nutrition is good compared to West Africa which is a third world region.
I agree that East Africans are gracile.
The Lion has a self-reported GRE IQ equivalent of 145, I believe.
Except lion never took the GRE.
He took the LSAT and the GMAT.
He took the GMAT twice. I sat for it once. 770 but 790 on the practice test. I’ve never taken the LSAT.
Lion is a prole from Staten Island.
Two recent examples:
He simply dismissed a meta-study of 50 studies which concluded alcoholism is not very heritable.
He simply dismissed the GDP per capita PPP figure for Cuba which is the same as Argentina’s and Chile’s and a little higher than Russia’s.
Why?
PROLES LOVE TRUTHINESS.
That is, if American mass media has “established” that Cuba is a failure and Communism is always bad then the FACT that it HAS worked in Cuba is simply dismissed.
OR
If it is “established” that alcoholism is “genetic” then the FACT that it isn’t is simply dismissed.
Lion talks about proles a lot. He is one.
“That is, if American mass media has “established” that Cuba is a failure and Communism is always bad then the FACT that it HAS worked in Cuba is simply dismissed.”
Dookie has no idea what has worked in Cuba. Like most guys who slavishly worship the state, he just accepts some standard dipshit Michael Moore narrative about the Castro Brothers implementing great health care in Havana that he has never bothered to actually check, other than perhaps the figures for life expectancy.
But those life expectancy figures were high in Cuba *before* the revolution. The country already compared favorably to other Latin American and Caribbean countries when Batista was still in power. Anyone interested in a more detailed explanation about Cuba and its human development can read about it here.
Lion and Dookie do share one thing in common. Neither one of them have the first clue about economics. They don’t even have a good instinctual grasp of what they ought to be looking for when discussing economics.
“He simply dismissed the GDP per capita PPP figure for Cuba which is the same as Argentina’s and Chile’s and a little higher than Russia’s.”
Dookie doesn’t have a scintilla of an iota of a clue what he’s talking about. This just needs to be pointed out again and again and again and again until people at this blog start to get it.
The data on Cuba’s economy is sketchy at best, and many organizations which measure those stats don’t include Cuba for that reason. But even the most optimistic accounting of that Caribbean country has it below Chile’s PPP per capita. The World Bank ranks Cuba 60th behind not only Chile (50th) but Latvia (52nd), Russia (43rd), Poland (46th), and even Croatia (55th). Cuba is just barely above that economic powerhouse Romania (61st).
The CIA ranks Cuba 94th in the world, below Serbia, Ecuador, and Macedonia – and well below Chile (57th), Russia (60th), and Argentina (58th). See relative stats here.
One might complain that the CIA hasn’t shown it’s very accurate when measuring the economies of communist countries, but that’s just the point. They’re hard to measure because they’re so opaque.
I haven’t even mentioned the point that perhaps PPP is a misleading stat to look at when judging Cuba, since it’s a small country which by necessity has to import a lot of goods which it can’t create itself. And if you look at the value of the Cuban economy when judged by market exchange rates, Cuba’s GDP per capita sinks even further. The World Bank, for example, ranks Cuba 90th by this measure, barely ahead of the Dominican Republic. Chile, Russia and Argentina all have more than double the nominal per capita wealth of Cuba.
Well the Lion reportedly got an IQ equivalent of 145 on one of the college admission tests; maybe it wasn’t the GRE.
And interesting image:
https://s3.amazonaws.com/ksr/projects/30981/posts/92543/image-50041-full.jpg?1309425976
One thing which is hard to miss is that NE Asians do have quite muscular legs, but less muscular upper bodies.
Africans tend to have less subcutaneous fat, so may appear more muscular than they are.
What’s meant by “linear”:
http://blogs.wsj.com/chinarealtime/2014/09/16/alibaba-ipo-is-innovation-with-chinese-characteristics/
This guy looks like alien. Certainly his head fits his wealth. Best way to judge some one’s IQ is his head size and wealth, not his words.
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This is illogical. Most of our greatest scientists, the smartest people in the world, have been overweight. Einstein, Teller, Schrodinger, Penrose, Friedman, etc. were all overweight. Most professors are overweight too. Most bankers. Most engineers. Hell, even doctors.
that’s what your own perception says. but science doesn’t care about one’s personnal feelings.
you are probably overweighted yourself to say this while facts contradict what you think.
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What of the heavily built? I have weighed around 250 lbs for most of my adult life, and it would be erroneous to describe Chris Langan as scrawny. When completing my engineering degree, my recollection was that my fellow students had bodies of all types with a tendency towards the average. Scrawniness was no more prevalent than amongst the taxi drivers or musicians that I knew.
Might it be that the intelligent have less developed musculature due to more time spent indoors reading or learning, having a distaste for the rather boring company of the less-witted?
Concerning Muhammad Ali (who has just died) – his alleged IQ of 78 seems grossly insufficient to generate the splendidly amusing and witty things that he was so fond of saying.
I don’t think iq and height ratio exists at later ages. In childhood, it may be due to nutrition which impact both height and iq.
I am 5′ 6.5″, average for an indian man. There are people who consider me very smart, even genius but over years, I have come to know three guys who are shorter than me (5’4″ -5’5″) and have proved themselves to be smarter, consistently. They don’t get Called geniuses. I guess due to shorter stature they don’t impress people enough.
I’m still learning from you, while I’m making my way to the top as well. I absolutely love reading everything that is posted on your blog.Keep the stories coming. I enjoyed it!
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