Answer:
Nine months old infants
Explanation:
Imitation is a process through which a child learns new behavior. When a child is not able to infer the behavior immediately, the child will make a representation in mind so he/she can use that same information in the same situation. The imitation procedure will guide the infants' memory for insight that the same situation occurs before so they can use that stored information.
The deferred imitation like a process in which an action is modeled after a delay without any prior motor skills or practice. This procedure is proposed to tap the declarative memory in infants who are not able to speak. Infants develop an ill-mannered memory.
Thus here Piaget defined the deferred imitation used by infants that do not occur before one and a half years before. But Metzoff shows infants could imitate the action they saw before 24 hours.