Why is it a sign that something may be amiss with a four-month old infant who is nto smiling in response to the smile of others?

A four-month-old infant typically begins to engage in social interactions, including smiling in response to others, as part of their emotional and social development. If a baby is not smiling back, it may indicate potential developmental delays or issues with social engagement. Early intervention can be crucial, so it’s important for caregivers to consult a pediatrician if they notice such signs. Monitoring other developmental milestones is also essential to assess the child's overall well-being.