If you pay attention to someone, they will naturally gravitate towards you more than someone who ignores them. That applies to a lot of living social animals, like dogs, but it so obviously applies to humans, too. You're going to want to hang out with the person who texts you regularly more than the guy who forgets you exist for 6 months and then invites you to a bad show his band is playing at.
This holds true for even the youngest humans. Babies will naturally gravitate towards those who hold them, feed them, and pay attention to them. Even if their sight isn't fully developed, they can smell, feel, and identify people in their life. That's the case for the 1-year-old baby in this story. She gravitates toward her 16-year-old sister because she is the one who picks her up when she cries and comforts her while she is teething. Their mom is not pleased that the baby favors her older daughter over her.
This image is for illustration only, and the subjects are models; the image does not depict the actual subjects of the story.
