Final answer:
Object permanence refers to the understanding that physical things continue to exist, even if they are hidden from us.
Step-by-step explanation:
Object permanence refers to the understanding that physical things continue to exist, even if they are hidden from us. It is the idea that even if something is out of sight, it still exists. This concept was first studied by developmental psychologist Jean Piaget and is a key milestone in cognitive development during infancy. Infants typically do not demonstrate object permanence until they are around 8-12 months old.