I'm no statistician, but I would guess that our best tools are studies of infant physiology with and apart from the mother, and an evolutionary perspective on the whole thing.  Without that perspective, it could be argued that a co-sleeping baby's physiology is unnaturally low in stress responses.  If we take the co-sleeping baby to be the evolutionary norm (duh!), we can find all sorts of abnormal responses in the solitary sleeping baby.  Those might be even more compelling to mothers than statistics, because they look at **a** baby (and she thinks **my** baby).  And then the stats from other countries can be used to bolster those "together is normal" conclusions.  But I think the cornerstone needs to be the research on infant sleep physiology.

Diane Wiessinger, MS, IBCLC, LLLL  Ithaca, NY  USA
www.normalfed.com

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