Besides the effects of the composition of the breast milk on the developing
brain, I think that the effects of not being sick so much has a significant
impact.  A baby that is sick can't pay attention to its environment as well
as a healthy baby.  And a parent who is tired from cleaning up vomit or
holding a screaming baby with an ear ache doesn't interact in the same ways
with his/her baby as the parent who has a pleasant, happy, healthy baby.  I
think these points are not even considered when effects of BF are
calculated.  So there are chemical, emotional and environmental factors to
be factored into the effects of BF!  Sincerely, Pat in SNJ