15 weeks old

A NEW TALENT FOR ROLLING OVER
When placed on her stomach, your baby will lift her head and shoulders high, using her arms for support. This mini push-up helps strengthen her muscles and gives her a better view of what's going on. She may even amaze you (and herself!) by rolling from her back to her front, or vice versa.

You can encourage this skill through play: Wiggle a toy next to the side she customarily rolls to in case she's interested enough to try again. Applaud her efforts and smile. She may need your reassurance since her new skill can be frightening.

GETTING MORE SELECTIVE ABOUT PEOPLE
By now, your baby may respond to your presence, your voice, and even your facial expressions by kicking and waving her arms. Your baby, who up to this point probably smiled at everyone she met, is also beginning to be picky about the company she keeps.

In large groups or with unfamiliar people, your baby may need time to get comfortable. Allow for transition time with strangers or when leaving her with a sitter.

When she's safely in your arms, though, she's likely to be interested in interacting with other people — especially noisy, boisterous children because they're more active, more amusing to a baby, and physically less imposing.