I’m still on vacation, but I’ve got just enough time to pop in with a quick link to a nice discussion about the link between heredity and IQ. While some have argued that as much of 75 percent of the variability in IQ is hereditary, more recent research suggests a more complex interaction. The key, as always, are studies on adoption of identical twins:
Regardless of whether the adopting families were rich or poor… children whose biological parents were well-off had I.Q. scores averaging 16 points higher than those from working-class parents. Yet what is really remarkable is how big a difference the adopting families’ backgrounds made all the same. The average I.Q. of children from well-to-do parents who were placed with families from the same social stratum was 119.6. But when such infants were adopted by poor families, their average I.Q. was 107.5 — 12 points lower. The same holds true for children born into impoverished families: youngsters adopted by parents of similarly modest means had average I.Q.’s of 92.4, while the I.Q.’s of those placed with well-off parents averaged 103.6. These studies confirm that environment matters — the only, and crucial, difference between these children is the lives they have led.
(via Kevin Drum)