Gifted Issues Discussion homepage Forums GT Research genetic basis for intelligence

Steve Hsu is a physics professor who also does research on intelligence. Below are some quotes from slides of a presentation he gave.

http://duende.uoregon.edu/~hsu/talks/g_colloquium.pdf
Investigating the genetic basis for intelligence
and other quantitative traits
Steve Hsu
University of Oregon and BGI

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General factor of intelligence

SAT, GRE heavily g-loaded: high correlation with g or IQ;
”SAT is an IQ test”
IQ: mean 100, SD 15 (normally distributed)
SAT (M+V): mean 1000, SD  200 (1995 ”recentering”)

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The far tail

Roe study (1950’s): 64 randomly selected eminent scientists had
IQs much higher than the general population of science PhDs.
Almost all of the eminent scientists in the sample scored above
+(3-4) SD in at least one of M / V categories.
Mean score in both categories was roughly +4 SD.
Average for science PhDs around +2 SD, so eminent group
highly atypical among scientists.
Positive returns to IQ > +2 SD in scientific research?

[The cited study is from the book "The Making of a Scientist" by Anne Roe]

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Your kids and regression

Assuming parental midpoint of n SD above the population
average, the kids’ IQ will be normally distributed about a mean
which is around +.6n with residual SD of about 13 points. (The
.6 could actually be anywhere in the range (.5, .7), but the SD
doesn’t vary much from choice of empirical inputs.)
So, e.g., for n = 4 (parental midpoint of 160 – very smart
parents!), the mean for the kids would be 136 with only a few
percent chance of any kid to surpass 160 (requires  2 SD
fluctuation). For n = 3 (parental midpoint of 145) the mean for
the kids would be 127 and the probability of exceeding 145 less
than 10 percent.

It contains some howlers, but overall, not bad for a physicist.

Moral of the story: Don't ask a physicist to teach you about a social science topic.

I read this opinion piece some time back and bookmarked it:
http://www.bigwowo.com/2011/10/the-perversity-of-human-biodiversity-a-k-a-scientific-racism/

What are the howlers?

Really?! So he's saying that it is highly unlikely that children will be smarter than their parents? I wonder what his n= for this study. Hmmmm . . . skeptical. . .

It's also clear that he didn't consult any teenagers about this. ALL of them are smarter than their parents, and have no qualms about telling you so...;)

Because of regression to the mean, the children of parents with above-average IQs will usually have lower IQs than their parents (but still higher than average), and the children of parents with below-average IQs will usually have higher IQs than their parents (but still lower than average).

All three of my kids are smarter than me - just ask them! And they aren't even teens yet... they must be prodigies

polarbear

I never had an IQ test but I can tell that my oldest is a carbon copy of me at twelve. My extended family concurs. I would be shocked if there were a significant difference in our IQs.

Yes. How you expect children's IQ to compare with their parents' depends heavily on your assumptions about the extent of genetic heritability, and (even if you think IQ is mostly genetically based) about exactly how its genetic basis works, and about how assortative mating works. (I think assortative mating, the fact that people tend to get together with people like them, has a strong influence on the environment a couple provides for their children, but I also think it's plausible that it has an influence on the genetics. There may be thousands of SNPs accounting for the genetic component of IQ, but I bet the sets of those SNPs held by parents are not independent.)

Just from observation, though, the idea that it's rare for children of highly intelligent parents to be as intelligent as their parents doesn't seem at all plausible to me, at least when we're talking about parents both highly successful in the scientific/technical domain. It would be interesting to see research that compared children of couples both with similar IQs who work in the same field and have other indications of having "the same kind of" high IQ with children of couples with similar IQ numbers but different "kinds", actually.


ETA: we've talked about this often on this site. Here is a post I wrote last year to explain that "regression to the mean" doesn't work the way people sometimes think. Short version: if you think children's IQ will regress towards the mean of the population, you have to ask yourself "which population?" Humans? Primates? Mammals? PhD scientists?