A child's ability to understand that an object still exists even when it is out of sight is called what?

The concept of a child's understanding that an object continues to exist even when it is not visible is known as object permanence. This cognitive milestone typically develops during the sensorimotor stage of development, as defined by psychologist Jean Piaget. Object permanence is crucial because it reflects an early cognitive understanding of the world, indicating that the child can mentally represent objects and their properties even when those objects are not directly observable. This understanding contributes to the child's ability to search for hidden objects and anticipate their reappearance.

The other concepts listed relate to different aspects of cognitive development. Horizontal decalage refers to the idea that children may master certain cognitive skills at different times rather than all at once. Conservation of an object involves understanding that certain properties, like volume or number, remain the same even when their appearance changes. Accommodation refers to the process of modifying existing cognitive schemas to incorporate new information. While all these concepts are important in the study of cognitive development, they do not specifically define the ability to recognize that objects exist even when out of sight, which is the essence of object permanence.