I find that parents will try a thing once (certain type of bottle and
nipple) and then, when it doesn't work, will switch to another.  So the
baby is asked, usually when hungry, to switch nipples, etc..every time
they try bottle feeding.  Tell them to slow down and try a thing for a
period of days before trying a new thing.  Babies tend to be
conservative!
Edie Armstrong BSN, IBCLC, Fairfax, Va.