the moro reflex

The most entertaining newborn reflex is the Moro, or startle, reflex. Whenever an infant feels like it's falling, or is startled, it will throw up its hands as if it's saying, "Whoa!"

The reflex is a holdover from our more ape-like days, in which baby apes would need to reach out to grab hold of mother's fur if falling while swinging through trees or eating bananas, or whatever it is that apes do all day.

startled asleep?

An unswaddled Peter often will fall asleep half-Moro, as if:
(1) he's anticipating some future startle and wants to be extra ready;
(2) he's actually in a perpetual state of half-startle;
or, my personal bet
(3) he's fallen asleep half-way through his reflex, as if he couldn't be bothered to finish.