When do babies recognize or "know" someone?

[P.J.]

My SIL comes once a week for 4 hours to help with the baby. This has been going on for about 4-6 weeks now. Last week DS smiled when he first saw her, but then again he smiles at people we meet on the street, it doesn't necessarily mean anything. After how many of these caretaking sessions will DS feel like he's with someone he knows rather than a stranger?

I was wondering when and/or how to tell if a baby recognizes someone? How many times do they have to meet, or how much time do they have to spend together before the baby recognizes the smell, voice, sight of a particular person?

Likewise my mother's coming for a visit next week, it'll be the first time she's met our baby (who's almost 4 m.o.), and she's only staying a week. I wonder how many days into her visit (we'll be spending pretty much the entire time together and w/DS) the baby will recognize her as someone other than a new unfamiliar stranger? And would he recognize her next time they meet, which won't be until December?

Any personal experience or research/developmental info you know would be appreciated. TIA!

[Dov'sMom]

Babies definitely have a sense of who they spend time with pretty early on. My mother lives with us two weeks out of three, and by three-four months, my baby definitely knew who she was when she came back from the week away. Some babies already have stranger anxiety! Your baby will learn your mother immediately, and will remember her day-to-day as long as she spends a lot fo time with him.

I don't know if he'll remember all the way to December, though, from four months. My oldest son remembered his grandmother when he didn't see her between 7 months and 10 months, but I don't think he remembered from 4 months to 7 months. My second son saw his grandparents at 3 months, 9 months, and 15 months. He did not recognize them at 9 months, but definitely at 15 months. Each visit was about a week.

[rhiOrion]

My dd definitely knew her dad by the time she was your baby's age. She has a special HUUUUUUGE grin reserved just for him when he walks in the door. Other people can get that grin out of her by being silly, but he only has to appear.

[busymama77]

Originally Posted by rhiOrion

My dd definitely knew her dad by the time she was your baby's age. She has a special HUUUUUUGE grin reserved just for him when he walks in the door. Other people can get that grin out of her by being silly, but he only has to appear.

Aww, that's so sweet.