A recent study found that smart children demand more stimulation.
Quoting a commenter on Steve Sailer's blog
http://www.blogger.com/comment.g?blogID=9430835&postID=7167347658738183037

Quote
Tucker-Drob and Harden have published one such study. They had a sample of 650 MZ and DZ twin pairs for whom measures of cognitive ability and parental cognitive stimulation were available for ages 2 and 4.

They found that parental cognitive stimulation explained a substantial amount of children's cognitive ability differences at age 2 and 4, and that controlling for age-2 cognitive ability, differences in parental cognitive stimulation at age 2 explained a substantial amount of cognitive ability differences at age 4. So, parenting indeed appeared to boost intelligence.
However, they also found that age-2 cognitive ability predicted the quality of parental cognitive stimulation provided at age 4, AND that this association was entirely mediated by genetic effects that affected both age-2 cognitive ability and age-4 cognitive stimulation. As they put it, this "suggests that parents adjust the level of cognitive stimulation that they provide in response to their children’s genetic predispositions for
cognitive ability. In other words, genetic differences in early cognitive ability evoke differential levels of stimulation
from parents."
Here is the paper:

http://homepage.psy.utexas.edu/homepage/group/TuckerDrobLAB/website/pdf/Tucker-Drob%20&%20Harden%20(in%20press,%20Developmental%20Science)%20Reciprocal%20G-E%20Transactions.pdf
Early childhood cognitive development and parental cognitive
stimulation: evidence for reciprocal gene–environment transactions
Elliot M. Tucker-Drob and K. Paige Harden
Developmental Science (2011), pp 1–10

"To see what is in front of one's nose needs a constant struggle." - George Orwell