In addition in the previously linked slides he seems to present the regression to the mean of IQ scores in children as a fact, but in this blog post it's obviously conjecture.
There will be regression to the mean in IQ as long the correlation between the IQ of children and the average IQ of their parents is less than one. A lot of research has found this to be the case. Hsu is not breaking new ground here. Galton discussed regression to the mean in the 1800s.
Really? Galton discussed regression to the mean of IQ scores in children of highly gifted parents that long ago, or did he just discuss height? Does Hsu have some source for his assertions of hard facts, for example the .6 factor etc., or are they just based on fiddlings with numbers in turn based on his assumptions of how it might work, with an admittedly simplified model, while demonstrating lack of knowledge of how the calculations ought to be made, and while allowing that the real world might not be that way? Stating some basic ideas about regression to the mean in general is not enough to convince me in this context.
Here is what the Wikipedia says about the heritability of IQ
http://en.wikipedia.org/wiki/Heritability_of_IQ#Estimates_of_the_heritability_of_IQ .
"Various studies have found the heritability of IQ to be between 0.7 and 0.8 in adults and 0.45 in childhood in the United States.[6][16][17] It may seem reasonable to expect that genetic influences on traits like IQ should become less important as one gains experiences with age. However, that the opposite occurs is well documented. Heritability measures in infancy are as low as 0.2, around 0.4 in middle childhood, and as high as 0.8 in adulthood.[7][18] One proposed explanation is that people with different genes tend to seek out different environments that reinforce the effects of those genes.[6]
A 1994 review in Behavior Genetics based on identical/fraternal twin studies found that heritability is as high as 0.80 in general cognitive ability but it also varies based on the trait, with .60 for verbal tests, .50 for spatial and speed-of-processing tests, and only .40 for memory tests.[5]
In 2006, The New York Times Magazine listed about three quarters as a figure held by the majority of studies,[8] while a 2004 meta-analysis of reports in Current Directions in Psychological Science gave an overall estimate of around .85 for 18-year-olds and older.[7]"
The site has the citations. The level of heritability depends on how "child IQ" is measured. Hsu's 0.6 estimate is not implausible. As long as heritability of IQ is significantly less than one -- and all researchers have found that to be the case -- there will be some regression to the mean in IQ, just as there is in other human traits, such as height and athletic ability.
