The term "object permanence" is used to describe a child's ability to know that objects continue to exist even though they can no longer be seen or heard.

If you have ever played a game of "peek-a-boo" with a very young child, then you probably understand how this works. When an object is hidden from sight, infants under a certain age often become upset that the item has vanished. This is because they are too young to understand that the object continues to exist even though it cannot be seen.

Object Permanence

The concept of object permanence plays a significant role in the theory of cognitive development created by psychologist Jean Piaget. In the sensorimotor stage of development, a period that lasts from birth to about age two, Piaget suggested that children understand the world through their motor abilities such as touch, vision, taste, and movement.﻿﻿

During early infancy, babies are extremely egocentric. They have no concept that the world exists separate from their point of view and experience. To understand that objects continue to exist even when they are unseen, infants must first develop a mental representation of the object.

Schemas

Piaget referred to these mental images as schemas. A schema is a category of knowledge about something in the world. For example, an infant might have a schema for food, which during early infancy will be either a bottle or breast.

As the child grows older and has more experiences, their schemas will multiply and become much more complex. Through the processes of assimilation and accommodation, children develop new mental categories, expand their existing categories, and even completely change their current schemas.﻿﻿

How Object Permanence Develops

Piaget suggested that there were six substages that occur during the sensorimotor stage of development, including:

Birth to 1 Month: Reflexes

During the earliest part of the sensorimotor stage, reflexes are the primary way that infants understand and explore the world. Reflexive responses such as rooting, sucking, and startling are how the infant interacts with his or her environment.

1 to 4 Months: Development of New Schemas

Next, primary circular reactions lead to the formation of new schemas. A baby might accidentally suck on his thumb and realize that it's enjoyable. He will then repeat the action because he finds it pleasurable.

4 to 8 Months: Intentional Actions

Around the age of 4 to 8 months, infants begin paying much more attention to the world around them. They will even perform actions to create a response. Piaget referred to these as secondary circular reactions.

8 to 12 Months: Greater Exploration

Between 8 and 12 months, intentional actions become much more evident. Babies will shake toys to produce sounds and their responses to the environment become more cohesive and coordinated.

12 to 18 Months: Trial-and-Error

Tertiary circular reactions appear during the fifth stage. These involve trial-and-error and infants might start performing actions to gain attention from others.

18 to 24 Months: Object Permanence Emerges

Piaget believed that representational thought begins to emerge between 18 and 24 months. At this point, children become able to form mental representations of objects. Because they can symbolically imagine things that cannot be seen, they are now able to understand object permanence.﻿﻿

Object Permanence

To determine if object permanence was present, Piaget would show a toy to an infant before hiding it or taking it away. In one version of his experiment, Piaget would hide a toy under a blanket and then observe to see if the infant would search for the object.

Some of the infants would appear confused or upset by the loss while other infants would instead look for the object.

Piaget believed that the children who were upset that the toy was gone lacked the understanding of object permanence, while those who searched for the toy had reached this developmental milestone.

In Piaget’s experiments, this tended to occur around the age of 8 to 9 months.﻿﻿

Recent Findings

While Piaget’s theory was enormously influential and remains quite popular today, it has also been the subject of criticism. One of the major criticisms of Piaget’s work is that he often underestimated children’s abilities.

Research on object permanence has also called into question some of Piaget's conclusions. Researchers have been able to demonstrate that with cues, children as young as four months can understand that objects continue to exist even though they are unseen or unheard.﻿﻿

Other researchers have suggested alternative explanations for why infants do not look for hidden toys. Very young children simply may not have the physical coordination necessary to search for the item. In other cases, babies might not have an interest in finding the hidden object.﻿﻿