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Pumpkin Person

Monthly Archives: October 2019

Henry: Portrait of a Serial Killer (1990)

31 Thursday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 16 Comments

Tags

Henry Lee Lucas, Henry: Portrait of a Serial Killer, IQ, mental retardation, Otis Toole, serial killers

pumpkin person rating: 8/10

In the spirit of Halloween, I re-watched this movie a couple weekends ago. Neither Netflix, the Movie network, nor pay per view have enough selection for me, so I added Amazon Prime to boot and this film was prominently displayed in their horror section.

It’s a disturbing, well organized film based on real life serial killers Henry Lee Lucas and Otis Toole.

Psychiatrists reportedly found Toole to be be schizophrenic, psychopathic, and mentally retarded with IQ scores ranging from 54 (Trainable [moderate] Retardation) to 75 (Borderline Retardation). It’s hard to assign a single number, but assuming the lowest and highest score were from tests that correlate around 0.7, a composite IQ of 61 is implied (Educable [mild] Retardation).

Actually it’s likely his IQs was even lower because in those days people didn’t know about the Flynn effect inflating the scores of people tested using old norms.

Toole’s low IQ seems to be part of a larger pattern of neurological impairment. He was also epileptic and sexually aroused by fire and from his mug shot it seems he had asymmetrical features, suggesting genetic mutations or developmental insults..

Toole’s art therapist Dr. Joel Norris described Toole as “the lower end of the gene pool”. The genetic garbage of society. Indeed in the film his body is literally stuffed into a garbage bag.

Of course HBD deniers could argue his problems were cultural, not biological. Raised by a mother who dressed him up as a girl, a sister and male neighbor who raped him, and a grave robbing granny, the illiterate Toole drops out of school to become a prostitute and part-time transvestite. Toole’s horrific backstory is not shown in the film.

Toole would become close friends with Henry Lee Lucas, whose mother also made him wear a dress as a kid. With a much higher IQ of 87, Lucas is widely believed to have been the leader of their murder spree.

While the film never mentions IQ it does imply Lucas is the smarter of the two, warning Toole not to kill people he’s been seen with.

Although Lucas towers over Toole intellectually, both men are morons compared to a quick-witted overweight TV salesman who belittles them with biting sarcasm. Luckily the sarcasm flies above their heads, but when the high IQ salesman pushes his luck, he proves too clever by half.

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Scene from Rob Zombie’s Halloween

30 Wednesday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 80 Comments

With Halloween only a few days away, I though I’d share this scene from Rob Zombie’s Halloween.

Many people hated Zombie’s 2007 remake of the 1978 classic because it turned Michael Myers from a middle class kid to white trash. They also felt Zombie’s dialogue was gratuitously disgusting, however this is how Zombie remembers kids talking when he was growing up.

One of the first things we notice is that young Myers has a low social IQ (or at least low impulse control). Rather than laughing off his bullies’ taunts, he descends into rage, the exact reaction his bullies were hoping for.

More importantly, Myers says “F@*CK YOU” to the school principal. This is where Myers crosses the line from normal bad behavior (getting into fights at school) to pathological, clinical, and diagnostically significant. Even the principal is nonplussed because such behavior is so outside the norm. Clearly Myers is the most deranged kid he has ever seen in say 30 years working in schools. Telling the principal to “F@*CK YOU” is such a violation of social norms that it implies he’s dealing with a psychopath.

Lastly, we see how the correlation between genes and environment increases with age. Because of Myers’s bad behavior, he goes from having a lower class social environment to being locked in a mental hospital room to rot. His genetically low IQ and low impulse control cause him to make rash decisions which quickly drag his environment down to his genetic level.

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Are the Tarahumara an example of reaction norms?

20 Sunday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 264 Comments

For years commenter Mug of Pee has been saying that HBDers naively assume the Phenotype = Genotype + Environment model.

A good example of this model is sex and height. For example in 1914, the average Canadian man was 5’7″ and the average Canadian woman was 5’2″. Then after 100 years of modern nutrition and health, the average Canadian man is 5’10” and the average Canadian woman is 5’4″.

So even though environment added a few inches of height to both sexes, it did not change the male > female rank order and if expressed in SD units, may not have even changed the gap. The P = G + E model sees environment as a rising tide that lifts all boats but doesn’t change their relative heights. No matter what the environment, having a Y chromosome predicts greater height, while no matter what the genome, 20th century nutrition predicts greater height. In other words, both the genetic effect and the environmental effect are independent of one another and thus can be added together.

By contrast the reaction norm model sees environmental effects as lifting only some boats, while at the same time sinking others. So rather than adding environmental effects to genetic effects, you either add or subtract depending on which environmental effect combines with genomic effect.

While I thought this model was interesting, I couldn’t think of many real world examples.

Then one night I was watching the The evolution of us, a two part documentary on both netflix and amazon prime, which features such luminaries as John Hawkings, Steve Hsu, and Daniel Lieberman. The documentary briefly discussed the Tarahumara.

In their native Copper Canyon environment, the Tarahumara are extremely fit and slim and can outrun white athletes who come and visit, yet when they move to urban areas, they appear to be several standard deviations fatter than white people..

It’s not surprising that the Tarahumara are fatter in an urban environment than in a pre-industrial one (that’s true of all populations). But the fact that they are so disproportionately penalized by an urban environment might be an example of reaction norms.

Of course I know of no evidence of the cognitive equivalent of the Tarahumara: a group that scores as high or higher than whites in one environment, yet scores lower in another.

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IQ, social environment & DNA

17 Thursday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 156 Comments

Tags

Arthur Jensen, equal environment assumption, IQ, James Flyyn, shared environment, social class

Commenter RR argues that IQ tests measure social class. If by social class he means the home one grew up in, the following author begs to differ:

First, family has little effect on whatever cognitive abilities you have after the age of 17. While family environment is potent early on, its effects fade away to low level by age 17 and become insignificant by maturity. As you grow up, you move outside the family and go to school, become a member of a peer group (your close friends), find a job, and marry. You enter a current environment that swamps the lingering effects of family environment. Current environment is surprisingly self-contained: it influences one’s current cognitive abilities with very little interference from past environments. Most of us assume that your early family environment leaves some indelible mark on your intelligence throughout life. But the literature shows this simply isn’t so.

Second, once the influence of family disappears, the cognitive quality of your current environment tends to match your genetic quality. This is often called the tendency toward “gene-environment co-relation”. This means simply that if your genes are at the 90th percentile for cognitive ability, your current environment tends to be at the 90th percentile of the population for cognitive quality…In other words, chance events aide, genes and current environment tend to match, so whatever genetic differences exist predict cognitive performance without any need to take current environment into account.

You might think the above was written by Arthur Jensen, but it was written by Jensen’s most formidable opponent, James Flynn. It’s from pages 5 to 6 of Flynn’s book Does Your Family Make You Smarter?

Evidence in support of Flynn’s comments is a 2010 study by Haworth et al, where an astonishing 11000 pairs of twins from four different countries were intelligence tested. The results: heritability was 41% at age nine, 55% at age 12, and 66% by age 17.

66% is very similar to the WAIS IQ heritability found in the Minnesota study of twins reared apart, but Haworth et al compared the IQ correlation of MZ twins raised together with the correlation of DZ twins raised together (the classical twin study). If one assumes that both types of twins are equally similar in their environments (including prenatal), the greater IQ similarity found among MZ twins can only be explained by their greater genomic similarity. This is known as the equal environment assumption.

Critics claim that MZ twins raised together enjoy more similar environments than DZ twins raised together and so genes are getting undeserved credit for an environmental effect. However Arthur Jensen notes:

…some same-sex DZ twins look much more alike than others. In some cases their parents even wrongly believe that their DZ twins are identical twins, and they treat them as such by dressing them alike and giving them the same hairstyles and so on. But DZ twins whose parents and others had mistaken them for MZ twins are no more alike in IQ than other DZ twins or ordinary siblings who don’t look much alike.

Source: Intelligence, Race and Genetics by Frank Miele, pg 98

Indeed if people think MZ twins have more similar environments than DZ twins because they look identical, then it follows that same sex DZ twins should have more similar environments than opposite sex DZ twins because they too look more similar (and are treated more similarly) and yet the IQ correlation between same sex and opposite sex MZ twins are virtually identical.

Further support for the equal environment assumption comes from a study of 1,030 female-female twin pairs from the Virginia Twin Registry with known zygosity. About 15% of the twins disagreed with their actual zygosity, however perceived zygosity had no impact on the correlation between twins when it came to any of the five psychiatric disorders studied.

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Polygenic IQ scores

15 Tuesday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 132 Comments

Tags

95% confidence interval, Gregory Clark, IQ, Neanderthals, polygenic scores, Richard Klein, standard error, Upper Paleolithic Revolution

Commenter “Some Guy” had some questions about polygenic scores for me. His questions are in block quotes with my answers directly below each one.

How good do you think polygenic scores will have to get before they start getting used on an individual level? Like within how many SDs of the true IQ/g/educational achievement?

If one’s polygenic score is extreme enough, it doesn’t have to be very accurate at all to give useful information. For example, let’s say you have several embryos to choose from and one has a polygenic education score of +5 SD. Even though such scores only predict 12% of the variance, because +5 SD is so extreme, you can be about 97% confident that embryo will grow up to be more educated than the average person (assuming he or she is raised in a society similar to the one from which the stats were derived).

One problem with polygenic scores is they don’t seem translate well from one culture to another, suggesting they’re more correlative than causal.

The uses I can think of is to identify children with high potential from poor backgrounds, or as an environmentally unbiased entrance “exam” for schools etc.

What I would like to see them be used for is to estimate the IQs of historical Geniuses like Albert Einstein and to estimate the IQs of ancient human populations. For example Richard Klein believes there was a major genetic change in human cognition that occurred about 50 kya that allowed us to suddenly spread from Africa, replace the Neanderthals, colonize the globe and create representational art. If we compared the polygenic scores of humans both before and after the upper Paleolitic revolution, we could test this idea. Similarly Gregory Clark believes rapid genetic evolution in Europe allowed the industrial revolution.

I would also love to see polygenic IQ scores for the Neanderthals, assuming they would be meaningful in a group that culturally and genomically distinct.

What sort of PGS-IQ correlation would result in polygenic scores that are say within 1 SD of the true IQ? I know you often calculate standard errors from correlations, mind sharing the formula/method?

Within 1 SD with degree of certainty? If you mean with 95% certainty, you would need a correlation of 0.85+ which I doubt will ever be achieved. Even the correlation between two different IQ tests is seldom that high.

The method is to square the correlation to get the percentage of the variance explained, and then subtract that value from 1 to see what percentage is left unexplained.

So for example a PGS that correlated 0.85 with IQ explains 72% of the IQ variance, thus leaving 28% unexplained.

The variance is defined as the standard deviation squared, so since the IQ standard deviation is set at 15, the variance is 225, and 28% of 225 is 63.

The square root of 63 is 7.9 which is what the standard deviation would be if everyone had the same PGS. This is also known as the standard error of the estimate. Now in a bell curve, 95% fall within 1.96 of the mean, so multiplying 7.9 by 1.96 tells us that 95% of say the UK, will have IQs within 15.5 points of the PGS prediction.

So if you have a PGS of +2 SD that correlates 0.85 with IQ, your IQ will likely be 0.85(2) = +1.7 or IQ 126, with a 95% confidence interval of 111 to 142. But of course we’re nowhere near seeing a 0.85 correlation.

To get the general public to really trust polygenic scores for IQ, I’d guess the accuracy would have to be within 5 points of the true score. Within 10 points would lead to people who actually differ by 20 points regularly ending up with the same polygenic score. Since 20 points tend to be the difference between leaders and followers, such errors would be highly noticeable.

I think if they achieved a correlation of 0.7 with IQ they’d be considered credible (especially if the predictive power was maintained across oceans and generations). That’s the correlation between different IQ type tests with each-other and these are routinely used to decide issues as important as who gets into an elite college, who gets excluded from the military, who gets diagnosed as disabled or gifted, and who gets sentenced to death by the courts.

By the way, what do you think about this argument against people who consider intelligence entirely environmental: If that really was the case, then disadvantaged people would NEVER be smarter than people with good backgrounds. So why even bother giving people from poor backgrounds a chance? 100% environmentalism leads to un-egalitarian conclusions, and is easily disproven by the existence of smart disadvantage people.

It’s prima facie absurd, but it wouldn’t necessarily lead to the conclusion that we shouldn’t give deprived people a chance. On the contrary it might lead to the conclusion that changing IQ is simply a matter of changing environments.

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A closer look at Bill Gates’s IQ

13 Sunday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 76 Comments

Tags

Bill Gates, IQ, SAT scores

Bill Gates reportedly scored 1590 on the SAT in the early 1970s (Verbal 790 + Math 800). In a rare study done in 1974, it was estimated that if all American teens took the SAT that year (instead of just the college bound elite) , the verbal mean would be 368 (SD 111) and the math would be 402 (SD 112). Assuming a 0.67 correlation between the two subscales, a combined mean of 770 (SD 203.8) is implied.

Thus Gates’s scores equated to a verbal IQ of 157, a math IQ of 153+, and a combined IQ of 160.

However these numbers assume the SAT was normally distributed, and yet empirical data from the 1980s suggests near perfect scores were much more rare than the normal curve predicts and equated to an IQ of about 170 and if anything they were likely even more rare in the 1970s when fewer people studied for the SAT.

Another reason why these numbers likely underestimate Gates’s IQ is that he hit the ceiling on the math section.

Thus I found the following part of a 2001 article in Time magazine of interest:

“In ninth grade,” Gates recalls over dinner one night, “I came up with a new form of rebellion. I hadn’t been getting good grades, but I decided to get all A’s without taking a book home. I didn’t go to math class, because I knew enough and had read ahead, and I placed within the top 10 people in the nation on an aptitude exam. That established my independence and taught me I didn’t need to rebel anymore.” By 10th grade he was teaching computers and writing a program that handled class scheduling, which had a secret function that placed him in classes with the right girls.

According to this source, there were 4,097,000 Americans born the same year Gates was.  Some of them would have died before reaching the ninth grade, but these probably would have been made up for by immigrants, so Gates being in the top ten in the nation for his age or grade level, implies he scored in the top one in 409,700.  This equates to a math IQ of 168.

In other words, had the SAT had a higher ceiling in the 1970s, he would have perhaps scored 910 (the equivalent of IQ 168). Add this to his verbal score of 790, and we get a combined score of 1700, which would have equated to a combined IQ of about 170. So even if we assume 1970s SAT scores were normally distributed, Gates still clocks in at IQ 170 as long as we extend the ceiling.

Commenter Bruno has expressed considerable skepticism about Gates having an IQ this high, citing the fact that he was not the top math student at Harvard.

My response is that a) standardized test scores should be given more weight than school grades, and b) Gates spent his teens obsessing over computers so math IQ made him the best programmer at Harvard instead of the best math student per se. The title of best math student probably went to an equally smart person who spent their teens obsessing over math.

The video clips are from the fascinating new Netflix series Inside Bill’s Brain.

It seems Gates has really mellowed out in recent decades, or at least become better at hiding his arrogance. In the below clip you can see him berating his employees and making a bizarre head twirling facial expression as if implying the employee is mentally retarded.

Indeed with an IQ of 170, even the average member of America’s political, economic, and cultural elite (IQ 125 to 135) is literally mentally retarded compared to Gates, which helps explain how he was able to leapfrog over the establishment to become the richest man of the 20th century, with such a stranglehold over the market that it took the U.S. justice department to stop his complete domination.

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Charles Murray & the strangely high ceiling of the old SAT

12 Saturday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 8 Comments

On page 694 of the book The Bell Curve by Richard J. Herrnstein and Charles Murray, they mention that the U.S. average on the verbal SAT during the 1980s if all U.S. 17-year-olds took the test, not just the college-bound elite. This data was arrived at using special studies by the college board, where they recruited a nationally representative sample of teens to take the SAT.

But I wanted to know the standard deviation of the math SAT. I knew over a decade ago, but had since forgotten. I reached out to the author of the study Murray cited, but he no longer had a copy of his own paper.

“Why don’t you ask Charles Murray?” somebody said.

“Charles Murray is the most influential social scientist on the planet. He ain’t gona respond to some nobody blogger” I replied.

“But you’re not just any blogger, you’re Pumpkin Person! Never underestimate the power of that brand” they said citing my lucrative advertising deal with wordpress which has been earning money on top of money.

So I sent off a message to the World’s most influential social scientist, not expecting any reply.

He responded IMMEDIATELY.

“Okay, okay, I’ll see if I can find it” he wrote on February 18, 2019.

Precisely 12 minutes later he wrote:

“Verbal mean 375.8, SD 102. Math mean 411.5, SD 109…”

The most influential social scientists on the planet managed to dig up a paper he hadn’t cited in a quarter century with incredible speed and was kind enough to also take an iphone photograph from one of the pages.

But how do we determine the SD for the combined old SAT?  Well since we know the estimated means and SD of the subscales, then the below formula is useful for calculating the composite SD (from page 779 of the book The Bell Curve by Herrnstein and Murray):

formula

r is the correlation between the two tests that make up the composite and σ is the standard deviation of the two tests.

Herrnstein and Murray claim that for the SAT population, the correlation between SAT verbal and SAT math is 0.67. Assuming it would be the same for the general U.S. 17-year-old population, then the 1980s SAT had an SD of 192.8

Some might argue that the 0.67 correlation in the SAT population would underestimate the correlation in the general U.S. 17-year-old population, because the SAT sample is a restricted group and thus should be corrected for range restriction. .

However surprisingly, the math SAT standard deviation for the SAT population was 119 in the 1980s (higher than the 109 in the general population).

Source: Trends in educational achievement
By Daniel M. Koretz, United States. Congressional Budget Office

So assuming that if all U.S. 17-year-olds had taken the SAT in the 1980s, the combined mean would be 787.3 with an SD of 192.8, then a near perfect score of 1590 would have equated to +4.16 SD or an IQ equivalent of 162.

However as I wrote back in March 2018:

The above conversions were based on the assumption that the SAT would have a roughly normal distribution in the general U.S. population, which is likely true for 99% of Americans but likely false at the extremes.

Below is incredibly rare data of the total number of people in 1984 who scored high on the combined SAT.

sat1984

Table IV

We see that of the 3,521,000 Americans born in 1967, roughly 964,739 would grow up to take the SAT at age 17 in 1984.  And of those who did, only 20,443 scored above 1330.  If one assumes, as the great Ron Hoeflin does, that virtually all the top SAT talent took the SAT in 1984 (and whatever shortfall was madeup for by foreign students), then those 20,443 were not just the best of the 964,739 who actually took the SAT, but the best of all 3,521,000 Americans their age.  This equates to the one in 172 level or IQ 138+ (U.S. norms).

Meanwhile, only five of the 3,521,000 U.S. babies born in 1967 would grow up to score 1590+ on the SAT, so 1590+ is one in 704,200 level, or IQ 170+.  However above I claimed that in the mid 1980s, the combined SAT had a mean of 787 and an estimated SD of 220, which means 1590 is “only” +3.65 SD or IQ 155.  Clearly the SAT is not normally distributed at the high extreme, so Z scores start to dramatically underestimate normalized Z scores, and modern IQ scales only care about the latter.

Thus, for extremely high SAT scores obtained in the mid 1980s, please use table V and not formula IV:

Table V:

1984 satiq equivalent(u.s. norms) based on normalized Z scores(sd 15)
1600170+
1590170
1580164
1570163
1560161
1550159
1540157
1530156
1520154
1510153
1500152
1490150
1480150
1470148
1460147
1450146
1440146
1430145
1420144
1410143
1400142
1390141
1380141
1370140
1360139
1350139
1340138
1330137

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9 second social IQ test

04 Friday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 353 Comments

Tags

social intelligence, social IQ

Please watch the 9 second video below and then answer the question “Why should he have been watched every minute?”.

If you know what this clip is from, kindly refrain from spoiling it for others.

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Cultural bias on IQ tests

03 Thursday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 46 Comments

Commenter RR has a left a series of comments on this blog denying the very idea of culture fair IQ tests.

For example he writes:

. CULTURE-FREE IQ TESTS ARE AN IMPOSSIBILITY AS ALL HUMAN COGNIZING TAKES PLACE IN A CULTURAL CONTEXT!

This is a tautology not a testable hypothesis. The concept of culture bias needs to be operationalized if it wants scientific credibility.

In the field of psychometrics, a test is typically defined as culturally biased if the regression line predicting school performance from IQ is different in one group than another. For example, if blacks with an IQ of 120 get an A in algebra (on average), but whites with IQs of 120 get only a B, then the test is said to be culturally biased against blacks.

Why? Because if the test is underpredicting the grades of black kids, then it’s probably also underpredicting their intelligence as well.

The literature on predictive bias is extensive and it turns out that by this definition, neither IQ tests nor college admission tests are biased against any visible minority group in the United States. Indeed just the opposite, the tests tend to overpredict black achievement, and thus might even be considered biased against whites!

However this definition assumes that the criterion that test is predicting (i.e. school grades) is itself free from bias, but what could be more culturally loaded than school (the place where culture is explicitly taught).

Perhaps a better criterion than school grades would be real world survival skills. We could dump people in the middle of the woods and see how long they take to find their way out (each person would have a GPS locator they couldn’t use but could be used to find them) or have people compete in mock warfare like paintball. Again, if blacks with an IQ of 120 performed as well as whites with an IQ of 120 on these tasks (equating for practice and physical fitness), then IQ tests are unlikely to be culturally biased. But if 120 IQ blacks dominated 120 IQ whites, then it’s likely the tests are underestimating their intelligence.

Another way of testing for culture bias, as Jensen has alluded to, is to compare groups on physiological measures of intelligence like MRI brain size, evoked brain potentials, nerve conduction speed, neural adaptability reaction time etc. Jensen estimates that a comprehensive battery of such tests would correlate > 0.5 with IQ and this would be ideal for testing for culture bias. If for example, the nation of Nepal scored 3.8 standard deviations below the UK mean on tests like the Raven we would want them to take the physiological measure of intelligence.

The > 0.5 correlation would between IQ and its physiological proxies predicts that Nepal would score at least 3.8(0.5) = 1.9 SD below UK norms on physiological measures, but if they would score much better than this (and they would) we would know that the IQ test was culturally biased against them, and thus is dramatically underestimating their neurology.

We can never say, categorically, than any given test is culture fair, but what we can say is that test A is culture fair with respect to cultures B and C. For example in the 1920s it was proven that hardcore performance tests (similar to Block Design and Object Assembly subtests on the WAIS) are culture fair to people with and without schooling. I wrote the following in 2014:

… excellent research in the 1920s showed that canal boat children who lived a nomadic existence where they were virtually deprived of schooling, showed massive declines in IQ as they got older. Because IQ tests are normed for age, and because these kids were kept out of school they fell further and further behind their chronological age-mates on the type of knowledge that IQ tests measure. Young canal boat kids would have an IQ around 90, but older canal boat kids would have an IQ of 60. However in a footnote on page 1001 of this document, scholar Arthur Jensen writes:

When the canal boat children were tested on nonverbal performance tests, there was much less decline in scores and the average IQ of the children was 82, which is a typical value for unskilled workers, as the canal boat people were. Fewer than 1 in 10 obtained performance IQs below 70, and in fact there was a slight positive correlation between performance IQ and age

This demonstrates that some IQ tests really do come close to the culture fair ideal. People understood that in the 1920s, but decades of post-modern propaganda has brainwashed generations of credulous university students into thinking otherwise.

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Robert Mugabe’s IQ

02 Wednesday Oct 2019

Posted by pumpkinperson in Uncategorized

≈ 78 Comments

Tags

Africa, education, IQ, Robert Mugabe

photo taken July 1, 1984. ALEXANDER JOE/AFP/Getty Images

Several people have asked me to estimate the IQ of late Zimbabwean leader Robert Mugabe.

According to the latest research by Richard Lynn and David Becker, the average IQ of sub-Saharan Africa is 69 however I would argue that if the data is limited to the most culture reduced tests (and I don’t mean the Raven, which is deceptively culturally loaded), it would be about 80 (UK norms/white norms). It’s important to use the most culturally reduced tests when comparing populations separated by time or space, otherwise you get ridiculous results like average IQ increasing by 7 points a decade as happened in Holland on the Raven test.

80 is 20 points the white mean of 100. If black Africans average 20 points below white populations on truly culture reduced tests, then perhaps their leaders average 20 points below the white leaders of mostly white countries.

Publicly available data suggests U.S. presidents have an average IQ of 130 (with an SD of only 12 compared to the national white SD set at 15), so let’s say black African leaders have an average IQ of 110 (SD also 12).

However Mugabe was not just any black African leader. He was exceptionally well educated, even by the standards of World leaders.

To compare Mugabe’s education to other African leaders of his generation, I found a list of the oldest presidents in Africa and tried to determine how many degrees each had. Excluding non-black leaders, the 8 oldest held the following number of degrees:

Paul Biya 4, Manuel Pinto da Costa 0?, Alpha Condé 2?, Arthur Peter Mutharika 2, Hage Geingob 3, Teodoro Obiang Nguema Mbasogo 0?, Emmerson Dambudzo Mnangagwa 2?, Alassane Ouattara 3.

The mean is 2 with a standard deviation of 1.41

So with an astonishing seven university degrees Mugabe is 3.55 SD more educated than even a group as elite as African presidents

In sub-Saharan Africa, the correlation between culture-reduced IQ and education appears to be 0.52, but in a group as homogeneous as African presidents, it would likely be lower. What is needed is the IQ vs education correlation among a specific occupation (African Presidents).

On page 345 of his book Bias in Mental Testing, Arthur Jensen shows the partial correlation between IQ and education, that is the correlation holding occupation constant. This correlation is listed as 0.27 to 0.42 (see below). Let’s split the difference and say 0.35 and assume the same correlation in Africa..

Assuming Mugabe is 3.55 SD more educated than the average African president, the partial correlation predicts his IQ would be 0.35(3.55 SD) = 1.24 SD higher than the average African presidents.

Assuming African presidents have a mean IQ of 110 with an SD of 12 (see above), this would put his expected IQ at 125 (higher than 95% of white America).

All we can say with 95% certainty is that his IQ would be anywhere from 103 to 147. One reason for thinking he’s in the upper end of this range is that he was a Marxist, and left-wing politics are positively correlated with IQ (at least if you control for race and income).

Whatever his IQ, it would have likely been substantially higher had he been born and raised in the United States, where First World nutrition would have allowed his brain size to reach its genomic potential.

One caveat to the above analysis: usually education is measured by highest degree obtained, not number of degrees. How this might affect the correlation with IQ is unclear.

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