Ed Tronick, PhD is one of the leading authorities on infant development. His collaboration with the famous pediatrician, Berry Brazelton, MD was instrumental in the development of Brazelton Neonatal Assessment Scale. His Still Face Experiment with mothers and infant monumental in demonstrating the social competence infants. A link to a video demonstration is listed below
https://youtu.be/YTTSXc6sARg
Your Anxious Child