Baby boys sleep lighter than girls

Baby boys die from SIDS more often than girls do, so it was not implausible that boys should be harder to rouse from sleep than girls, but it turns out to be not so. For the first month or so, boys are more easily awakened by a puff of air than girls are, and by 2 or 3 months, there is no difference. On to some other plausible reason.

And yes, I did have a very nice vacation, thank you.