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Unread November 19th, 2007, 04:45 PM
James Brody James Brody is offline
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Join Date: Jun 2004
Location: Philadelphia area
Posts: 1,143
Default IQ: GxE & time

posted 11/19/07

"Environments and occupants amplify each other with the result is that some traits, measured intelligence for example, grow from a 0.20 heritability when you are four years old to 0.80 when you are in your sixties. (Plomin, 1994; Segal, 2007)" from Brody, in press. In other words, people who start out just a little smarter will find experiences that multiply those initial differences over a lifetime. So goes Plomin's explanation.

Start with the argument in Plomin (1994), look up Segal's paper, and then spend some time with DeFries et al.

The finding is surprising but appears to be robust. And once you are into the model, any other conclusion becomes unbelievable!



Segal NL, McGuire SA, Havlena J, Gill P, & Scott L. (2007) Intellectual similarity of virtual twin pairs: Developmental trends. Pers Individ Dif. 2007 May ; 42(7): 1209–1219. Available at See also Segal N (1999) Entwined Lives: Twins and What They Tell Us about Human Behavior. NY: Dutton.
DeFries J, McGuffin, P., McClearn G, & Plomin, R. (2000) Behavioral Genetics (4th ed.) NY: Worth.
Plomin, R. (1994) Genetics and Experience: The Interplay between Nature and Nurture. Thousand Oaks, CA: Sage.
Plomin, R. & DeFries, J. (1998) Genetics of cognitive abilities and disabilities. Scientific American. 278(5), 62-69.
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