Final answer:
Object permanence is associated with Piaget's sensorimotor stage, a crucial development phase from birth to 2 years old, during which children understand that objects continue to exist even when not visible.
Step-by-step explanation:
Object permanence is associated with Piaget's sensorimotor stage, which is the first stage in his theory of cognitive development. This stage occurs from birth to approximately 2 years old. During the sensorimotor stage, children learn about the world around them using their senses and motor actions. It's between the ages of 5 and 8 months that a child typically develops object permanence, which is the realization that objects continue to exist even when they cannot be observed. This concept signifies a fundamental step in cognitive development, as young infants who have not yet grasped object permanence will behave as if a hidden object has ceased to exist, whereas older infants will search for the object, indicating their understanding that it still exists.