Here are more details about the video I referenced:
"The Still Face paradigm, designed by Edward Tronick, is an experimental procedure for studying infant social and emotional development. During the experiment, an infant and a parent interact playfully before the parent suddenly stops responding and looks away. After a short period, the parent reengages with the infant. The infant’s reaction to a suddenly unresponsive parent and his or her behavior when the parent resumes interaction, have been used to study many aspects of early social and emotional development."
"This video clip is excerpted from ZERO TO THREE's Helping Babies From the Bench: Using the Science of Early Childhood Development in Court."
References:
http://www.zerotothree.org/child-development/early-childhood-mental-health/