How IQ is affected by genetics and Envinronment

An important study indicates
that breastfeeding is effective in raising IQ by about six
points, but only for the large portion of the population
having one of two alleles at a particular site that regulates
fatty acids and is influenced by breast milk (Caspi et al.,
2007). Those having another allele at that site did not
benefit from breastfeeding, but people with that allele are in
a small minority. This finding of genetic contingency
speaks against the possibility of a social-class confound in
the breastfeeding–IQ relationship, because the benefit of
breastfeeding occurred for children with the two more
common alleles regardless of the mother’s social class and
did not occur for children with the less common allele,
again regardless of social class. Moreover, it was only the
child’s allele at the relevant site, not the mother’s, that
mediated the influence on IQ. Another study manipulated
breastfeeding in a large randomized control study and also
found about a 0.5 SD difference in IQ (Kramer, 2008).

https://www.apa.org/pubs/journals/releases/amp-67-2-130.pdf

Have the right genes (expressed by the right alleles) and exposed to the correct nutrition and you achieve a higher IQ.

Originally posted by Eladar
[b] An important study indicates
that breastfeeding is effective in raising IQ by about six
points, but only for the large portion of the population
having one of two alleles at a particular site that regulates
fatty acids and is influenced by breast milk (Caspi et al.,
2007). Those having another allele at that site did not
benefit from breastfeeding, ...[text shortened]... xpressed by the right alleles) and exposed to the correct nutrition and you achieve a higher IQ.