Infants have the ability to distinguish among faces from their own ethnic group this is called

Object permanence describes 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.

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.

In order to understand that objects continue to exist even when they are unseen, infants must first develop a mental representation of the object.

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.

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.

One consequence of the development of object permanence is the emergence of separation anxiety. Once infants know that objects and people persist when they are no longer in sight, they often become upset when parents and caretakers are no longer visible.

Fortunately, this anxiety tends to be temporary and usually goes away by age 3. In some cases, however, separation anxiety can become more severe and persistent.

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

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.

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.

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.

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.

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

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.

While Piaget’s theory was enormously influential and remains quite popular today, it has also been the subject of criticism. Research on object permanence has also called into question some of Piaget's conclusions.

One of the major criticisms of Piaget’s work is that he often underestimated children’s abilities. Children may be capable of more at an earlier age than Piaget originally suggested.

Researchers have been able to demonstrate that with cues, children as young as 4 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.

Interacting with and playing with your child is one of the best ways to help develop important skills such as object permanence. Simple games and play can give your child the opportunity to practice skills and explore the world around them. Some things you might do to support this skill include:

• Peekaboo: This classic, simple game is a quick and easy way to entertain your child. You might play the game by covering up your own face or hiding your child's toys behind another object. After hiding the toy, ask where it is before revealing the item.
• Hiding objects: Take a few of your child's toys and hide them in places your child can easily access. This might involve placing them behind another toy or tucking them under a blanket or pillow. Then encourage your child to search for the items. 

The emergence of object permanence is an important developmental milestone and marker of cognitive development in children. While originally believed to occur later during the sensorimotor stage of development, researchers now understand that infants are capable of this feat much earlier in life.

It is important to remember, however, that all children develop at different rates. If you are concerned about your child's understanding of object permanence or have another concern about a developmental milestone, talk to your child's doctor. In many cases, early intervention and treatment can lead to better outcomes.