What is a common emotional reaction of a 6-month-old infant when a parent leaves the room?

At 6 months of age, infants typically begin to develop attachments to their primary caregivers, which leads to a strong emotional response when separated from them. When a parent leaves the room, a common reaction is for the infant to cry and reach out for the parent. This behavior is indicative of separation anxiety, which usually starts to emerge between 6 to 8 months of age. Infants at this stage are beginning to understand object permanence—the concept that objects and people continue to exist even when they are out of sight—making their emotional reactions to separation more pronounced.

The other options do not accurately represent the expected behavior of a 6-month-old. An infant smiling and waving goodbye suggests a level of understanding and social engagement that typically isn't present at this early age. Showing no reaction might indicate a lack of attachment or a greater degree of maturity than is common for this developmental stage. Falling asleep immediately could occur, but it's less likely to be a typical reaction specifically linked to a parent's departure, as the emotional bond usually provokes a more responsive behavior.