When do children begin to understand that objects still exist outside their sight?

The understanding that objects continue to exist even when they are out of sight is known as object permanence. While this concept is a fundamental milestone in child cognitive development, the timeline for its emergence is more nuanced than once thought.

Swiss psychologist Jean Piaget originally proposed that this ability develops in stages during the sensorimotor stage, with the most significant progress occurring between 8 and 24 months of age. However, modern research suggests that the foundations of object permanence may emerge much earlier, with some studies identifying evidence of this cognitive skill in infants as young as 3.5 months old.1

Because development occurs at different rates for every child, there is no single age at which this understanding is finalized. Factors such as distraction or physical capability can influence how a child demonstrates this knowledge. Caregivers can support this development through interactive play, such as using pop-up books or playing games like peek-a-boo.1