Final answer:
Object permanence usually develops between 6-8 months old as part of the sensorimotor stage of cognitive development. This milestone signifies that a child understands objects continue to exist even when not visible, an essential aspect of cognitive growth.
Step-by-step explanation:
Object permanence typically develops during infancy, specifically between 6-8 months old. This cognitive milestone is part of the sensorimotor stage of development, outlined by psychologist Jean Piaget, which spans from birth to about 2 years old. At this stage, children begin to understand that objects continue to exist even when they cannot be seen or heard. The concept of object permanence is fundamental in cognitive development, leading to advancements in the child's ability to problem solve and understand the world. Infants who have developed object permanence will actively search for objects after they have been hidden, indicating their knowledge that these objects have not ceased to exist. This understanding is also linked to the display of stranger anxiety, as children begin to have a clearer concept of the familiar versus the unfamiliar. Cognitive development during infancy is rapid and includes a vast array of new skills and recognitions, with the acquisition of object permanence being a significant achievement.