Newly born infants do not have language. They create Nominal Graded messages.
These movements that communicate meaning are signs. (Keep in mind that these are different than the signs in Sign Language. We will see how later.)
Another important example of nominal graded communication is the crying of an infant in the first three months of life. No one teaches the baby how to communicate so effectively. It is instinctive and determined by internal body processes.
The degree of intensity (e.g., cooing versus crying) determines the message meaning. Interestingly, you and I are wired to respond to an infants cry, just as the bees who watch the dance are wired to respond to it.
Hence, the baby's cry is more compelling and is more difficult to ignore than you might expect, even for other babies. Put one crying baby in a nursery of ten, and soon you will have eleven crying babies.