WHY BABIES CRY: My perspective.
Think of babies as news reporters from another planet.
They don’t speak our language yet but they have VERY IMPORTANT INFORMATION to convey to us about a whole number of things.
Their Universal Translator takes about 3.5 years to fully calibrate but it begins effective translation process around 9 months of operation, give or take a few months, and some longer.
They report on their own internal state as well as the state of the world around them. At that point, they believe we are stupid creatures and need to be told everything, so they inform us of everything.
After a while, they begun to understand that we big creatures ARE somewhat of an intelligent species and report on fewer and fewer findings.