IQ

Stylized Facts

• Survey by Rushton and Jensen on race differences (and reaction time, etc.) in 2005. Very nicely written, lots of stuff.

• La Griffe du Lion essays.

• A good list of articles from various decades by Murray, etc.

• "Mind the Gap," Steve Sailer (2023), new study.

"Progressives have this insane tendency to assume that if it really is true that blacks aren’t as smart as whites on average, then the only logical thing to do would be to murder all of our fellow black citizens in Treblinka-style death camps. Why? Because, they apparently reason, only Nazis, as they’ve so often said, think blacks have lower mean IQs, so if it turns out that the IQ Nazis are right, well, that means Hitler should be our role model.

Or something. You can never quite get liberals to articulate why they are convinced it would be the end of the world if there are racial differences in intelligence, other than that’s the ditch they’ve decided to die in and it would be embarrassing for them to turn out to be wrong."

• Nathan Cofnas (2020) is a recent discussion of group differences in IQ.

"The adult Black–White IQ gap has remained stubbornly constant at approximately one standard deviation (15 IQ points) among cohorts born since around 1970 (Murray, 2007).

Dickens and Flynn (2006, Figure 3) indicate that, in 2002, the Black–White IQ gap in among 20-year-olds was approximately one standard deviation, or 15 points. Nisbett (2017) writes that “Dickens and Flynn found [the Black–White gap in IQ to be] around 9.5 points,” but this is only the gap if we include children (as R. Nisbett confirmed in a personal communication, December 24, 2018). ... Frisby and Beaujean (2015, Table 8) find a Black–White IQ gap of 1.16 standard deviations among a population-representative sample of adults used to norm the Wechsler Adult Intelligence Scale IV in 2007. Intensive interventions can raise IQ substantially during childhood when the heritability of IQ is low. But despite some misleading claims about the success of early intervention programs, gains tend to dissolve by late adolescence or early adulthood (Baumeister & Bacharach, 2000; Lipsey, Farran, & Durkin, 2018; Protzko, 2015). Adoption by white families – one of the most extreme interventions possible – has virtually no effect on the IQ of black adoptees by adulthood. Black children adopted by middle- and upper-middle-class white families in Minnesota obtained IQ scores at age 17 that were roughly identical to the African American average. Adoptees with one black biological parent obtained IQ scores that were intermediate between the black and white means (Loehlin, 2000, Table 9.3).2

Environmentalists never predicted that the Black–White IQ gap would, after reaching one standard deviation, remain impervious to early education, adoption, massive improvements in the socioeconomic status of Blacks, and the (apparent) waning of overt racism and discrimination.

Unlike heritability studies, GWAS can uncover specific genetic variants – or single-nucleotide polymorphisms (SNPs) – associated with IQ. In just the last couple years, GWAS has identified hundreds of such SNPs (Davies et al., 2018; Savage et al., 2018; Sniekers et al., 2017), which together explain around 11% of the variance in IQ (Allegrini et al., 2019).

• Linda Gottfredson (2000) has a few points of interest:

"Siblings differ among themselves by an average of 12 IQ points; strangers differ by an average of 17 IQ points."

There is no persuasive evidence that the IQ bell curves for different racial-ethnic groups are converging over time, and they differ as much when children leave high school as when they enter kindergarten.

A large, longitudinal study of ex-servicemen in Australia found that safe driving relates to IQ level. Rates of death from motor vehicle accidents doubled and then tripled across three ranges of normal IQ: In the 100-115 IQ range, there were 51 deaths per 10,000 men; at IQ 85-100, there were 92 deaths; and at IQ 80-85, there were 147 deaths.

The shared effects of a family environment on intelligence disappear with age. ...The heritability of intelligence fairly rapidly becomes the dominant influence, rising from 40 percent of the explanation of differences in IQ scores in the pre-school years, to 60 percent by adolescence, to 80 percent in old age.

Studies of children who have become siblings through adoption illustrate this counterintuitive discovery. They become less like one another as they get older, but more like their biological parents and biological siblings, whom they have never met. By adolescence, adopted siblings tend to be no more alike in IQ than complete strangers. On the other hand, identical twins reared apart are almost as similar as identical twins reared together and considerably more similar than fraternal twins reared together.

Special interventions to raise low IQ’s are somewhat successful with young children, but the effects of these interventions almost always fade out as children approach early adolescence.

• "The new genetics of intelligence", Nature Reviews

Robert Plomin1 and Sophie von Stumm (2018). Mainly on DNA correlations with intelligence, but has lots of general references. They assess the twin-and-relative studies estimate of how much of variance is explained by genetics as .50. Gene scores can explain .10, about 20% of the genetic component.

"After adolescence, the effect of shared family environmental influence on intelligence is negligible, which means that family environments have little effect on individual differences in the long run"

"results for intelligence using the IQ2 GWAS: the negative genetic correlation with schizophrenia (−0.20) and the positive genetic

correlations with height (0.10) and autism (0.21)33. The same LD score regression analysis33 found that intelligence significantly correlated genetically with many other traits, including Alzheimer disease (−0.36), smoking cessation (−0.32), intracranial volume (0.29), head circumference in infancy (0.28), depressive symptoms (−0.27), attention-­deficit–hyperactivity disorder (−0.27), having ever smoked (−0.23), longevity (0.22) and, of course, years of education (0.70)."

Age

• Twitter thread on small decline with age in longitudinal studies--it's mostly a cross-section artifact of the Flynn Effect."Cognitive ability declined on average by −0.05 SD between ages 50–70 years, then −0.28 SD from 70–85 years."

Animals

• Ape IQ, a g factor in various tasks.

• Tryon Rat Breeding (1940). It only took about three generations and then they didn't get any smarter. A survey of the literature that followed is "Gene-environment interaction in programming hippocampal plasticity: focus on adult neurogenesis,"Muriel Koehl,which talks about introducing environmental differences too.

• Arden, R., & Adams, M. J. (2016). A general intelligence factor in dogs. Intelligence, 55, 79–85. doi:10.1016/j.intell.2016.01.008.

See

• Bar graph of IQ of different breeds

History

• Iodine raised IQ in America by 3 points in 1920's

IQ across Countries

• A good twitter thread (2023) by Cremieux trying to cross-validate as well as giving a table of countries from other people's work.

Ideas on IQ

• If 95% of a population are dull, and 5% are brilliant, and IQ is genetic, then very likely most brilliant people have dull parents. .95*.1 = .095, and .05*.8 = .040.

Personality and IQ

• From Spencer Greenberg (2024) "What negative/bad traits do you think correlate with having a higher I.Q.?"

I took a look at our own data and some studies, and here are traits that commenters suggested were associated with a higher I.Q. that I believe are NOT ACTUALLY meaningfully higher among higher I.Q. people:

• Depression • Anxiety • Neuroticism (from the Big Five personality framework) • Disagreebleness • Impatience • Laziness • Addiction

There are also some traits that people mentioned that D.O. have some sort of relationship with I.Q., but the real relationship is complex, such as:

• Autism - more often than not, studies I've seen linked it to lower (not higher) overall I.Q., but it is sometimes associated with exceptional ability in specific tasks (which may lead to uneven scores across subtasks on I.Q. tests). For instance, some studies have found that people with autism perform better on Raven's Progressive Matrices relative to their performance on other I.Q. tasks. Raven's Matrices are a type of intelligence task where you have to say which symbol should fill in the blank spot to complete the pattern in a grid of symbols.

• Conscientiousness - some studies find that people with higher I.Q.s get lower scores on some aspects of the Big Five personality trait "conscientiousness." But the research is mixed. In a big study we ran, we found that mostly there wasn't much link, but there were some (small) negative correlations between I.Q. and some aspects of conscientiousness. In particular, higher I.Q. people were a bit *less* likely to agree that they "begin tasks right away" (r=-0.14), "are a workaholic" (r=-0.12), "don't stop until everything is perfect" (r=-0.16), and think that "laws should be strictly enforced" (r=-0.11).

• Emotional Intelligence (E.Q.) - in our research this cuts both ways. Higher I.Q. people performed better on a task we administered where they had to identify what emotion a person was experiencing based on an image of the person's face. However, high I.Q. people were also a bit less likely to agree with the statement "I express my feelings easily."

• Dark Triad-related traits like Machiavellianism, narcissism, and sadism - some studies find that these traits tend to be lower (not higher) in high I.Q. people, but the research is mixed. In our own study, we found Machiavellism was unrelated to I.Q., while narcissism and sadism were somewhat *lower* in higher I.Q. people (r=-0.15 and r=-0.27 when controlling for gender).

In a big study we ran (mostly on people in the U.S.), here are some traits we found to be positively correlated with I.Q. scores:

• the preference to sleep more hours per night (r=0.39) as well as how many hours they report sleeping weekly (r=0.33) - I have no idea why this is the case

• thinking that profound sounding (but actually randomly generated) statements are *not* actually profound (e.g., "The unexplainable reflects universal knowledge")

• less of an obsession with celebrities and feeling less of a bond with them (e.g., disagreeing that "If I met my favorite celebrity, and they asked me to do a favor for them, I would do it, even if it was illegal and dangerous." and disagreeing that "I am such a fan of my favorite celebrity that I think we share an indescribable bond between us.")

• enjoying the act of thinking (linked to "need for cognition")

• actively open-minded thinking (which involves being open-minded to viewpoints that contradict your own beliefs) and being accepting of people whose opinions you strongly disagree with, being able to express those opinions (e.g., being allowed to protest)

• thinking that people are mostly good (r=0.20)

• finding the world enticing or exciting (which is related to one of the big three "primal beliefs")

• perhaps being a bit less charismatic in some ways (e.g., higher I.Q. is linked to being less likely to agree that "group activities tend to be dull without me" at r=-0.29, and "I am very charismatic" at r=-0.16)

• being a bit more politically progressive and less spiritual and less religious

There are also some additional traits that I think are probably linked to higher I.Q. but I don't have data showing it, so these are more speculative.

In particular, I suspect that higher I.Q. people may have blind spots from the experience of feeling smart compared to their peers when growing up.

As Duncan Sabien put it: "If you've spent your entire life being told you were wrong and being proven right (b/c you were smarter than the people around you), then when you run into another genius who tells you that you're wrong, you have a LOT of memetic antibodies that will make it easier-than-it-should-be to write them off or dismiss them."

I also suspect that some high I.Q. people learn to get by without making a big effort when they are young (e.g., excelling in school without really trying), which may lead to counter productive beliefs in adulthood, such as that they don't need to try hard or that trying hard is a sign of not being smart.

Finally, I suspect that high I.Q. people tend to be more "in their heads" and less "embodied," though it's hard to know how to measure this or even how to precisely define it.

Reaction Time

• A Tweet with a good graph on reaction time and IQ.

Tests

Wonderlic Test

• 6 example questions. The test sees how many correct answers to 50 questions you can get in 12 minutes.

• Carl B. Dodrill, [https://pumpkinperson.com/2019/01/20/converting-wonderlic-scores-to-iq/ "An economical method for the evaluation of general intelligence in adults," Journal of consulting and clinical psychology (1981). This has a conversion from 1-50 score to IQ.

• "NFL Wonderlic Test Scores," Wonderlictestprep.com (2024).