3. Repetitive sounds.
“Particularly something called the bilabials; Pa-pa, Ma-ma, Ba-ba are the first and most common sounds infants can make. They are simple because the two lips are pressed together with a puff of air pushed through them. That is why most first utterances around the globe for mother, father and bottle use these sounds. They are easy to make and the infant can get some quick language control and feedback from their environment in this way. (Trust me, the first time your little one says Pa-Pa to you will be a peak experience.) To strengthen the connection, when you hear them making the sound, make it back. Eventually the two of you can start your own bilabial chorus.”
Top Ten Tips for New Dads from Daniel Tomasulo, PHD