IQ and what it means in adulthood

Beliavsky wrote:
On Nov 10, 7:02 pm, Sarah Vaughan wrote:

Anyway, it would probably help if I gave the context here - the debate
was about the studies showing a correlation between breastfeeding and
increased IQ, and - if that association is real and not due to a
confounder - what it means in practice. I must say I was never terribly
impressed by the kind of numbers I was hearing - in the studies being
discussed, the average difference was seven IQ points, which just didn't
really sound like that much in practice to me. But the question came
up, and it got me wondering whether I was right about that or not.

A recent article in the Washington Post
http://www.washingtonpost.com/wp-dyn...1001271_3.html
said

"A recent study by Scottish researchers asked whether the higher IQs
seen in breast-fed children are the result of the breast milk they got
or some other factor. By comparing the IQs of sibling pairs in which
one was breast-fed and the other not, it found that breast milk is
irrelevant to IQ and that the mother's IQ explains both the decision
to breast-feed and her children's IQ."

I don't what study is being referred to. A finding that breast milk is
irrelevant to IQ certainly contradicts conventional wisdom.

I seem to recall that some of the earlier studies on
preemies had random assignment, but that was a long time ago
so I might be misremembering.

The other thing is that I think it's been likely
all along that the IQ advantages to breastfeeding operate
mostly at the margins--in children who, for one reason or
another, are at a disadvantage. We also already know that
parental IQ is a big factor. (I think it's interesting to
wonder what would happen if paternal IQ were taken into
account in a similar study.) So, I would expect that parental
IQ would overwhelm a smaller effect that operates primarily
at the margins. These sorts of effects are hard to detect.
Also, as with most studies of breastfeeding, since duration
of breastfeeding is so low in general, it's an open question
whether it would make more of a difference if, say, breastfeeding
according to WHO guidelines would increase the effect of
breastfeeding on IQ.

Best wishes,
Ericka