Communication skills such as

•crying
•smiling
•looking at faces
•quiet when picked
up or comforted
•listening to
voices

Are milestones for an infant.

http://www.kamloopschildrenstherapy.org/so
cial-emotional-infant-milestones

http://www.kidspot.com.au/familyhealth/Development-Babys-first-year-Baby-social-and-emotional-development-newborn-to-3-months+2670+212+article.htm

Social and Emotional Development