Infants go through four developmental milestones in those are social and emotional, communication, physical, and cognitive. The infant bond grows between their parents stronger. At two months, they have a social smile. At four months, they start to keep eye contact and move their arms around in excitement (MyHealth.Alberta.ca, 2025). By six months, they have become more social. They also have their facial expressions and start to express anger, joy and disgust.