A nurse is assessing a 9-month-old infant who does not search for a toy after it is hidden under a blanket. Which developmental milestone is the infant not meeting?

Choice A reason: Social interaction involves engaging with caregivers and peers through smiling, babbling, and responding to voices. While important, it is not directly related to searching for hidden objects. Choice B reason: Emotional regulation refers to the infant’s ability to manage and express emotions appropriately. It is not assessed through object search behaviors. Choice C reason: Cause and effect is demonstrated when infants understand that actions lead to outcomes, such as pressing a button to hear a sound. While related to cognitive development, it does not explain the failure to search for hidden objects. Choice D reason: Object permanence is the understanding that objects continue to exist even when out of sight. By 9 months, infants typically begin to search for hidden toys, indicating this milestone. Failure to do so suggests a delay in developing object permanence.