Lee-Ann,
The best study I know of that documents a physiological basis for nipple
confusion is Blass, EM: "Behavioral and physiological consequences of
suckling in rat and human newborns."  Acta Paediatr Suppl 397:71(6),
1994, p71-76.
        This study takes advantage of the fact that infant rats have a
behavioral response to nursing, which can be suppressed by blocking a
certain class of opiod receptor in the brain.  The scientists opened the
mother's uterus 12 hours before the pups were due to be born, and
offered them either milk, water, or human abm, through either an
eyedropper or a rubber nipple.  They exhibited the behavioral response
only when receiving milk (bovine light cream, I beleive, which the
researchers say is close in composition to rat milk).  BUT, when they
were given the milk through the rubber nipple, they subsequently showed
that behavioral response when given the rubber nipple alone.  This means
that they generalized the neurochemical response to milk plus rubber
nipple to rubber nipple alone after ONE exposure to the coupled
stimulus.  The authors suggest that more caution should be used in
exposing human infants, particularly vulnerable preterm infants, to the
abm plus artificial nipple combination.
        I encourage everyone to read this important study.  I find it
interesting that the research was done in the US (in NY no less) and
published in the Scandinavian peds journal!
--
Catherine Watson Genna, IBCLC  NYC  mailto:[log in to unmask]