Let me explain how adults hypothesis test. Of course, I need only change his position in my arms to stop the crying. I believe he is crying because he is physically uncomfortable. That's a hypothesis. I didn't know that.
Babies can cry for lots of reasons after all.
It was just a guess based on previous experience, the definition of hypothesis. If not, I would need to rethink the situation and try a new hypothesis. This is good old-fashioned science, and it turns out that babies can do the same thing. A large body of evidence demonstrates that when a coin is placed under a dish, our youngest citizens actually believe the coin disappears. It takes awhile for them to really understand that the coin does not disappear even if it is hidden from view, that the coin has object constancy and will be there even if they don't see it.