Having a baby certainly makes you think about things.
Watching our daughter, Amelia, learn during her first six months has led me to wonder how much of what babies do is because we react to it. As an example, every time we've taken our daughter out in public (which hasn't been that often), she acts like a normal baby, tasting everything, sucking on her fingers, her Mom's hair, her clothing, etc.
People look at her, and say, "How cute!", and other compliments. But, as soon as her thumb goes into her mouth, the people around exclaim, and generally say something like, "Oh, look, she found her thumb!" Even though Amelia had been sucking on anything and everything within reach for the entire time, as soon as the thumb hits the mouth, it's a big deal.
So, the stereotype is that babies suck their thumbs. What we've found with Amelia is that babies suck and taste everything. But, the thumbs are what generate positive attention and feedback in the audience. Over time, that's going to cause babies to prefer thumb sucking to, for instance, finger sucking.
And then, just about the time that she figures out that sucking her thumb is a good way to get attention, she'll be old enough that we'll tell her to stop doing it. ;-)
Anyway, the main point is that our expectations, our stereotypes, can be self fulfilling prophecies, especially where babies are concerned. They thrive on love and attention, and will try to repeat behaviors that generate love and attention.
So what we're trying with Amelia is to give her the love and attention whatever she does, not just when she fulfills our expectations of what a baby should be. So far, so good, but check back here in about 18 years, and I'll let you know how it worked out.