Who’s This? Newborns don’t know much, but they look intently at faces. Repeated sensations become perceptions, so in about 6 weeks, this baby will smile at Dad, Mom, a stranger, the dog, and at every other face. If this father in Utah responds like typical fathers everywhere, by 6 months cognition will be apparent: The baby will chortle with joy at seeing him but become wary of unfamiliar faces.