Best friend had a baby two weeks ago. she is excited because the baby smiled at birth, and she believes that the smiling indicated attachment

Babies typically do not show social smiles until four to six weeks of age.
Any smiling before that time, it may not be deliberate. It's usually only a sign that the baby is comfortable, either they just urinated or they just ate.

At first, the baby  smiles at every one but after several months, most babies save their smiles for people they know.

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