Brain size, relative intelligence, sex and fat.

After re-reading the ludicrous (and I’ll explain why it’s ludicrous) assertion that women have an average IQ five points lower than the male claims from Lynn, I thought I’d dig up some of the facts and figures surrounding this flawed work.

First of all I’m going to put a link to this paper on relative brain size and intelligence by Tom Schoenemann, a professor whose specialist field is the evolution of the human brain. It has several numbers relevant to this subject:

Male:          (55.5 kg body weight, 1361 g brain weight)
Female:    (51.5 kg body weight, 1228 g brain weight)

As you can see, the human male appears to have a brain size proportionally slightly larger than the female. However, one thing  routinely ignored in all these measurements is fat. The average human male  (Western) carries a body fat of about 16%, women carry about 22%. Which means you need to calculate the relative brain size compared to non-fat mass, as fat is a null factor and as far as anyone can tell requires no processing power to control. My IQ at nine stone would be exactly the same if I weighed ten stone, although my relative brain size would have decreased due to the extra fat I now carried. This does not apply to long-term obesity which affects the brain, but the mere gaining of a few pounds has no known effect on IQ.

So from the numbers above the  you would have 25.52 g of brain per kg of body mass (male) vs 23.84 g (female). The female comes out as 93.4% the relative size of the male from this.

Factoring in the difference in body fat… 

 male       55.5- 8.88 (16% fat)  =  46.62  for 1361g, or 29.19g/kg

female    51.5 – 11.33 (22% fat) = 40.17 for 1228g, or  30.57g/kg

And all of a sudden the ‘large relative difference’ (16.6% here) between male and female brain size does a vanishing act. Here women actually seem to have a slightly larger relative brain size, although this may well be from the body fat percentages I used here being slightly askew. I’m not claiming that the percentage for body fat is 100% accurate, and if anyone reading this can link me to a study with the exact figures I’d be grateful, but you get the ballpark idea here.

In the Lynn study he comments how women seem to be doing better than men in spite of having a lower IQ; which suggests to me that the tests he and his colleagues were using were hinky. One of the main uses for IQ tests is to predict academic ability, and really all that Lynn’s test did was establish that his did not measure academic ability well in women or men, which pretty much proved it was slightly biased in favour of the male, and therefore not an accurate measure of intelligence. Gender biasing an IQ test is easy to do if you put in a few extra maths questions and remove a few language questions (in favour of the male). Something similar happened in the early days of IQ testing when a series of IQ tests found women to have a notably higher IQ, until they ‘balanced’ the test out.

This really goes towards ‘what are IQ tests and do they measure general intellegence’ debate. So far (poll a few psychologists) the consensus is that IQ tests are a real indicator of your general intelligence level and are a good predictor of your life outcome. If they weren’t relevant to real life/academic success, the only thing an IQ test would indicate would be how good you are at IQ tests, and your score wouldn’t be even remotely related to how smart you are (see earlier point about the tests Lynn used).

Going back to the Schoenemann paper, he makes it very clear that so far relative brain size and IQ are very strongly correlated:

“It is quite simply a myth that brain size and  IQ are empirically unrelated in modern populations.”

So far all the studies I’ve seen show a correlation between general brain size and IQ of about .4, which is statistically significant. I’m wondering if a more focused MRI/IQ brain size study vs non-fat body mass would reveal a much higher correlation for humans than this.

But essentially, functionally identical relative brain size (when fat is factored in) for male and female makes Lynn’s claims for a 5 point difference extremely hard to support, even more so when he admits that the tests used did not accurately predict academic outcome for the women who took them. In fact, he himself has commented on how racial difference in IQ are supported by the difference in relative brain mass. So how, with no quantitive difference between sexes in relative brain mass, can his claims for a lower average female IQ be correct?

It can’t.

Shame on you for bad science, Dr Lynn.

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19 responses to “Brain size, relative intelligence, sex and fat.

  1. Don’t feel too bad. Richard Lynn doesn’t like us Sicilians either. :-)

    http://racialreality.blogspot.com/2010/03/richard-lynn-on-italian-iq.html

    • Don’t feel too bad. Richard Lynn doesn’t like us Sicilians either.

      Damn, I didn’t realise I’d actually posted this before I checked it.. Oh well, it’s done now!

  2. Anyone reading this click onto Marks link… very educational.

  3. “In the Lynn study he comments how women seem to be doing better than men in spite of having a lower IQ…. One of the main uses for IQ tests is to predict academic ability, and really all that Lynn’s test did was establish that his did not measure academic ability well in women or men”

    Based on my personal experience, I do not find it even slightly surprising that women “do better” in spite of a slightly lower IQ. There is a tremendous favoritism toward women in university graduate programs. I personally was a victim of this. I was tutoring women in my graduate program who got better fellowships than I got, and also were kept for the Ph.D. while I was let go. What Lynn has done, is hit upon the fact that there is bias in determining who succeeds in academia.

    • is a tremendous favoritism toward women in university graduate programs.

      Strangely, I remember reading a study that showed outright favourtism to male post grad students a few years ago, it was in New Scientist and the results were phenomenally in the male favour.

      I’m more inclined to believe a study.

  4. You would really have to substract more than fat from equation. For example muscle mass is highly independant from number of neurons. When a person body-builds then muscle mass increases, while neural connection to muscles stay more-or-less the same. Thus men should have significantly lower number of neurons per muscle mass than women. You should also do correction for thicker bones in men.

  5. Please name the study. I want to see this piece of work. It certainly doesn’t represent my experience, nor the experience of one of my professors who told me directly that for a number of years after the notion came into vogue that “gender bias” had to be corrected it was very hard for a male to gain admission to a classics graduate program.

    Under Title 7 of the Civil Rights Act of 1965 academic programs are eliminated if they cannot enroll some quota of women. This is true even of understandably male-dominated fields.

    You may well have a study that shows some difference between male and female performance or enrollment in some academic program, which is falsely inferred to mean institutional bias, but I do not believe that you have any study that genuinely demonstrates anti-female academic bias in the US of recent decades.

    • Please name the study. I want to see this piece of work

      Read it a few years ago while working at an assay lab… I’ll google for it, but I’m not geting my hopes up. However, Since I am from the UK that stuff about quotas isn’t really relevant. And it was defintley less than 20 years ago.

      You may well have a study that shows some difference between male and female performance or enrollment in some academic program,

      No, my memory is very clear that it showed a strong and unfair bias in favour of selecting which students got to do work that would further their career- I can remember the word ‘striking’ in the desciption of how the professors perferred male students to do the extra work. How bloody patronising (and offensive) of you to just assume that the little woman can’t remember anything correctly. Unfortunately the title escapes me ( it was a long time ago) but I found this one…

      Testing for Bias Against Female Test Takers of the Graduate Management Admissions Test and Potential Impact on Admissions to Graduate Programs in Business

      In this study, the authors examined the relationship between scores on the Graduate Management Admissions Test (GMAT) and achievement in core academic courses. The authors used a sample that revealed the potentially differential academic performance of male and female MBA students (N = 334) within particular GMAT scoring cohorts. Results showed that, for the top scoring GMAT cohort, there was statistically significant evidence of bias against the women. The potential effect of this bias against women may affect admissions decisions to graduate programs in business, particularly at the most selective MBA programs.

      The science sees to disagre with you. The one I remember from the magazine was showing bias against female science post grads, but I can’t locate it on line.

      Any way, You are assuming Lynn’s works has to do with higher educational levels. By the law of numbers, where a very small percentage of people get into post grad work, this would have very little effect even if your (apparently foundless) claims were true. Women perform educational better even at more mundane levels with Lynns claimed lower (incorrectly) IQ’s

      You should also read this piece, which I read in New Scientist in the same era.


      Male Scientist Writes of Life as Female Scientist Biologist Who Underwent Sex Change Describes Biases Against Women

      It’s BS that women are enjoy positive discrimination in education. I’ve been in enough classes when I’ve said something to be ignored, and to then have the male next to me say exactly the same thing and have everyone agree with him and tell him what a wonderful idea he had.

      BTW, more examples of bias… this time from testing:

      The FairTest complaint argued that the lion’s share of National Merit Scholarships went to boys each year because they score higher on the PSAT/NMSQT, although girls earn better grades in both high school and college when matched for the same academic courses. Even the test-makers’ own research admits that the test underpredicts the performance of females and over-predicts the performance of males (see Examiner, Winter 1994-95, Summer 1993, and Spring 1992).

      Again, IQ tests need to accurately predict academic ouitcome and life outcome or they are meaningless puzzles.

      From the same organisation…

      A 1989 study by Phyllis Rosser, The SAT Gender Gap: Identifying the Causes, found that the vast majority of questions exhibiting large gender differences in correct answer rates are biased in favor of males, despite females’ superior academic performance. Rosser found that females generally did better on questions about relationships, aesthetics and the humanities, while males did better on questions about sports, the physical sciences and business.

      This conclusion is supported by an earlier study by ETS researcher Carol Dwyer, who provides some historical perspective on the gender gap in her 1976 report. She notes that it is common knowledge among test-makers that gender differences can be manipulated by simply selecting different test items. Dwyer cites as an example the fact that, for the first several years the SAT was offered, males scored higher than females on the Math section but females achieved higher scores on the Verbal section. ETS policy-makers determined that the Verbal test needed to be “balanced” more in favor of males, and added questions pertaining to politics, business and sports to the Verbal portion. Since that time, males have outscored females on both the Math and Verbal sections. Dwyer notes that no similar effort has been made to “balance” the Math section, and concludes that, “It could be done, but it has not been, and I believe that probably an unconscious form of sexism underlies this pattern. When females show the superior performance, ‘balancing’ is required; when males show the superior performance, no adjustments are necessary.

  6. By the way this argument about the relative sizes of the male and female brains is really moot, since they are structured differently. Even if they had exactly the same size and the same relative size, it would be no reason to conclude that they perform equally.

    As a matter of fact, we know that male and female brains do not perform equally on various tasks. Even Mathilda admits that.

    THEREFORE this notion that intelligence tests must be weighted to produce overall equal results for the sexes — which really means tweaking the definition of intelligence — is entirely political.

    • Even Mathilda admits that

      Admits? As if it’s something I’m forced to do. LOL

      The fact is historically most IQ tests have shown women and men perform the same (with a few exceptions which go both ways). Males are better at maths, girls better at english (except me). The mere fact women do bettereducationally with lower sats scores and a few points of the IQ tests is a defacto admission of bias in those tests- otherwise the tests are meaningless and don’t measure potential and are puzzles to pass the time.

      And no, it’s not ‘politcal’ I’m just a bloody stickler for accuracy. Lynns work is heinously tweaked to fit his own agenda, and the whole point of an IQ to is to measure intelligence with a particlar aim to predict academic ability. If it’s failing to predict this corretcly (the tesst Lynn used for example) then ergo it is not measuring potential properly and their tests need tweaking until they are correct.

  7. “No, my memory is very clear that it showed a strong and unfair bias in favour of selecting which students got to do work that would further their career- ”

    I have already stated that my experience here in the USA was exactly the opposite.

    “How bloody patronising (and offensive) of you to just assume that the little woman can’t remember anything correctly.”

    I am not assuming that you don’t remember the purport of the study. I am assuming that the study was politically motivated and tendentious and that you were inadequately skeptical.

    The proposition that a man who has undergone a “sex-change operation” (since there really is no such thing) would know what it is like to live as a woman, is ridiculous. These people are regarded as freaks by most normal people, I think. Again, you are not being sufficiently circumspect about your sources.

    If you want to say that males and females have the same average intelligence (ARE YOU NOT SAYING THAT?), and you want to say that this must be reflected in academic performance for the intelligence tests to be valid (YOU DEFINITELY SAID THAT), then you run into the problem that males at all levels are not doing as well as females. It starts in elementary school. If you want some figures, I can dig some up.

    I agree with the theory that the way education is conducted today is feminized and has an implicit anti-male bias. I believe that because it is in total conformity with my experience! On top of that, I have taught in government schools here, and the bureacracy and staff are overwhelmingly female. What other explanation would you offer?

    • then you run into the problem that males at all levels are not doing as well as females

      Makes you wonder if males may not have the lower IQ then :)

      I am not assuming that you don’t remember the purport of the study.

      Actually that was what you said, pretty much.

      Funny how when a test shows females performing better (this didn’t just happen on the sats but on some early IQ tests) it is quickly corrected to assist the boys, but tests that favour males- nothing happens.

      I find it interesting that you claim everything that disagrees with you is ‘politically motivated’. Maybe the science just disagrees with you, did you ever consider that? It’s fairly obvious from what you’ve posted that you feel some woman has got something you thought you were entitled to, and this is the driving force behind your comments. You seem to have a horror of males not being in control or dominant. Women do better? must be the fault of the sysytem, not that women make better students.

      I find it entertaining that you are claiming men are more intelligent even though they do worse educationally (I looked up the American figures) and are also way more prone to end up in prison. So what exactly defines intelligence to you? Because your ‘more intelligent’ males don’t seem to be doing at all well.

      BTW, one of the major reasons behind male academic failure is plain bad behaviour, from pre school into college. Not that men are better students/more intelligent and the system is biased against them. The issue is that given a level playing field women make slightly better students, and that’s why they do better. It’s the males own fault if they spend their spare time partying and playing video games instead of studying.

      FYI, for white Americans the gender composition of colleges is pretty balanced: 51 percent female and 49 percent male, according to the National Education Association. Most the ‘excess’ females come from other ethnic backgrounds where men have other issues to contend with.

      One concession I will make, is that coursework based qualifications favour typically female brain development, which is why I always sucked at them. Give me a stress filled cramming session and one big exam any day. What’s the alternative- pick one that favours male development? Or allow different exams types to be taken?

  8. On second look, I think I may have misinterpreted the direction of the “sex-change” in the title of your linked article. Whether it was a male or female who had the genital alteration, the person who undergoes this cannot be taken as a typical.

  9. “It’s fairly obvious from what you’ve posted that you feel some woman has got something you thought you were entitled to, and this is the driving force behind your comments.”

    Yeah, when the women asking for my assistance had teaching fellowships that I couldn’t get, and when they were kept for the Ph.D. program while I was let go, it most definitely drew my attention to the existence of an anti-male bias. It is a bias that is implicit in the earlier years of education and becomes explicit in graduate school.

    Here’s a little book that touches on the problem, written by a woman. http://books.google.com/books?id=cnieFlrhxgoC&printsec=frontcover&dq=%22War+against+boys%22&hl=en&ei=qdntS8X6NcH-8Aa_o-z9Cg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCkQ6AEwAA#v=onepage&q&f=false

  10. Mathilda, you seem to assume that intelligence is the only thing that determines educational success. It is an unfounded assumption. For example, if you participate in classes actively and study hard for your exams, you will get better grades than someone who has a higher IQ but is lazier. In other words, the big five personality trait conscientiousness may be as good a predictor of academic success as IQ.

    Your claim that intelligence tests are biased because they may underpredict female academic performance relative to men rests on the assumption that the non-intelligence traits that affect performance are identically distributed in men and women. I don’t believe it is true. Girls and women tend to work harder in school, whereas many more boys and men are slackers.

    • Mathilda, you seem to assume that intelligence is the only thing that determines educational success.

      No, actually if you read the long argument with Hadding you’ll see that’s not the case. Given a level playing field women surpass men as students. I just fail to see how this can tally with claims for female lower average intelligence (from a minority sources too, I may add). Most studies place women as equal, and a few actually placed females as higher. The issue is that if the tests only predict how good you are at puzzles they are meaningless to real life intelligence levels. The fact that the amount of brain per kg when adjusted for fat is the same doesn’t support a higher male IQ.

  11. JL says: “Girls and women tend to work harder in school, whereas many more boys and men are slackers.”

    This is consistent with a point that Christina Hoff Sommers makes in The War against Boys, that the relaxation of discipline in schools under the influence of progressive ideas (and I might add, mostly feminine administration) has been particularly harmful for boys.

    Mathilda’s response does not withstand scrutiny. What is a “level playing field”? Is a school with lax discipline a level playing field? Is a school where almost all the teachers are female a level playing field? In some sense they are, but the characteristics of those environments are nonetheless more favorable to females than to males.

    What are these “real life intelligence levels” of which Mathilda speaks — in contrast to the ability to do mathematics, which she derides as “puzzles” — and how can they possibly be measured? Many factors other than intelligence figure into career success, including factors like “who you know or who you blow”. The most intelligent people, who are inclined to pursue ideas for their own sake, may end up with a low status in our money-driven society, but within Mathilda’s conceptual framework this is incomprehensible.

    My position on IQ tests is that they can be tweaked to favor either males or females, just by changing the weights given to verbal, analytical, and mathematical abilities. Since male and female intelligence are qualitatively different it doesn’t make much sense to talk about them being generally equal or unequal.

    It’s like saying that the female rats’ ability to respond to operant conditioning is “equal” to the male rats’ ability to navigate a maze. It’s like saying that an apple is equal to a biscuit. If however an environment were created in which responding to conditioning were the key to survival and independent trailblazing were punished, the male rats would be at a severe disadvantage.

    I am only discussing here the incidental and implicit anti-male bias in our society. I am not even bringing up again the fact that there is deliberate anti-male bias based on chasing the chimaera of correcting alleged past injustices.

    • What disturbs me is how keen you and JL are to insist a group with better academic skills and the same reltive brain mass have lower IQ’s (and that’s what you have been claiming prior). Does this not strike you as a bizarre statement?


      IQ tests have predictive validity for both men and women, even if they may underpredict the performance of women (or men) in some tasks

      So IQ being predictive is valid for men but not women? Thats a contradiction.

      in contrast to the ability to do mathematics, which she derides as “puzzles”

      No, I never derided maths. I just pointed out that if the tests aren’t predictive then they aren’t a measure of intelligence. And they don’t predict for women. You are very keen to put words into my mouth. I happen to ace the maths/logic section on IQ tests and I’m less good at the verbal (I have male pattern for my test results and behaviour).

      I would like to point out ad nauseum that the vast majority of IQ tests (adult and juvenille) don’t show a gender gap, but you choose to ignore them, which is my other beef with Lynn and his ilk. The ones that do show a male advantage (like the SATS) are acknowledged to have a gender bias; and you don’t get the lowest percentiles (more males) keen to take them which also boosts the male score by ditching dead weight. My mother taught special ed, mainly boys, and most of these don’t get to any exam taking stage. Half the backwards kids have dropped out before this point. And a big chunk of the males with real learning difficulties won’t even be attending schools or writing, let alone taking tests. A lot of very low performing males are never tested. Fewer low performing females (distribution curve diffrence at play) are excluded.

      Please read..

      Null Sex Differences in General Intelligence: Evidence from the WAIS-III

      There is an increasing number of studies claiming that the sex differences in general intelligence are “real.”
      The empirical evidence is based on the summation of the standardized sex differences in several cognitive
      batteries. However, the scientific construct of general ability rests on the correlations among test scores,
      rather than on their summation. The latter (ability in general) is an arbitrary variable, not a scientific
      construct. General ability is not a function of any particular cognitive test, but a source of variance evidenced
      by the correlation between several diverse tests, each of which reflects general ability (g) to some extent,
      but also group factors and test specificity. Because there are important educational, economic, and social
      consequences of a group difference in general ability, it is especially germane to evaluate the possibility
      of an average sex difference in its proxy measures, such as IQ. The Spanish standardization of the WAISIII
      is analyzed in the present study. The sample was made up of 703 females and 666 males, aged 15-94,
      drawn as a representative sample of the population in terms of educational level and geographical location.
      Although a male advantage of 3.6 IQ points is observed, the difference is in “ability in general,” not in
      “general ability”
      (g). Given that the main ingredient of the strong association between IQ and a broad
      range of social correlates is g, and given that there is no sex difference in g, then the average IQ sexdifference
      favoring males must be attributed to specific group factors and test specificity.

      More or less making the point I’ve made over and over..

      The concept of general ability, defined as g, rests on the
      correlations among test scores rather
      than on their summation.The latter (ability in general) is
      an arbitrary variable, not a scientific construct.

      Given that the main ingredient of the association
      between IQ and these social correlates is g, and given that
      there is no sex difference in g, it must be concluded that
      the average IQ sex difference is attributable (by default) to
      group factors and/or to test specificity.
      Therefore, the
      functional difference between the sexes in the real settings
      where g is functioning must be expected to be negligible.
      This evidence must be considered in the practical assessment
      of intelligence.

      According to you and JL, the only valid measure of IQ would seem to be mathmetical ability. The fact is we have the same amount of processing power, it’s just used a bit differently.

      am only discussing here the incidental and implicit anti-male bias in our society.

      What absolute bullshit. The fact is you aren’t allowed to openly bias in the favour of males the way that you feel you ‘deserve’ Hadding. A simple look at pay for the same job, and that women need higher grades to get into college blow that whiney claim of yours out of the water. So you’d obviously like a system in favour of males? How is that fair to girls? If you want to split their education feel free though, I’d go for that. Girls do better without boys around.I’d also like to point out, zero brain affecting mutations are carried on the Y chr, which has a very limited function. You’d need to argue that testosterone makes you smarter (as opposed to more inclined to get into trouble). And that comment about bone mass.. you do realise that’s more likely to add relative mass to the female brain right?

      Why cling to so bizarre a POV I wonder? It really reads as if you are just desperate to cling onto some way to feel superior.

  12. No, actually if you read the long argument with Hadding you’ll see that’s not the case. Given a level playing field women surpass men as students. I just fail to see how this can tally with claims for female lower average intelligence (from a minority sources too, I may add).

    I just told you how: because women work harder, on average. Working hard ≠ intelligence.

    Moreover, even if the average woman beats the average man academically, at the highest levels of achievement men surpass women by a wide margin.

    When comparing male and female intelligence, you need representative samples of adults, because boys mature slower than girls, many reaching their maximum IQ only in their early 20s. Most datasets used in these comparisons deal with teenagers. Moreover, you should use strongly g-loaded tests, because IQ tests derive just about all of their predictive validity from g.

    The issue is that if the tests only predict how good you are at puzzles they are meaningless to real life intelligence levels.

    IQ tests have predictive validity for both men and women, even if they may underpredict the performance of women (or men) in some tasks. This is only natural, because IQ alone does not determine any outcome, and the distributions of, for example, personality traits are different in men and women. If you compare women only to other women, the predictive validity may be stronger than if you include men, and vice versa.

    The fact that the amount of brain per kg when adjusted for fat is the same doesn’t support a higher male IQ.

    As pointed out above, for your calculations to make sense, you will also have to control for the fact that men have more muscle mass and a heavier skeleton. However, because male and female brains are different in many ways, these raw size comparisons are relatively meaningless in any case.

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