What developmental milestone is expected at about 9 months of age?

At around 9 months of age, one significant developmental milestone observed in infants is the emergence of stranger anxiety, which is a behavioral manifestation of their growing awareness and differentiation of familiar versus unfamiliar individuals. This developmental stage reflects an infant's attachment to their primary caregivers and an awareness of their environment. At this age, babies start to exhibit signs of distress or discomfort when approached by strangers, which indicates their developing social and emotional understanding.

While babbling and imitating actions are also important milestones that typically occur around this age, showing anxiety towards strangers is more characteristic of the 9-month mark. Running is not an expected milestone until much later in development, usually around the age of 12-18 months when children refine their gross motor skills. Understanding these milestones helps caregivers and healthcare providers gauge an infant's social and emotional development effectively.