0-6 Weeks: Reflexive Smile
You'll spot your newborn's first grin when he's asleep. You'll see him twitch, startle, and -- is that a smile? "During REM sleep your baby's body goes through physiological changes that activate certain reflexes, and one of those is a smile," says Pamela Garcy, PhD, a clinical psychologist in Dallas. At this point it's probably just a physical reaction, not an emotional sign.