In Piaget’s theory, the sensorimotor stage is first, and it is defined as the period when infants “think” by means of their senses and motor actions. As every new parent will attest, infants continually touch, manipulate, look, listen to, and even bite and chew objects. According to Piaget, these actions allow them to learn about the world and are crucial to their early cognitive development.
The infant’s actions allow the child to represent (or construct simple concepts of) objects and events. A toy
animal may be just a confusing array of sensations at first, but by looking, feeling, and manipulating it repeatedly, the child gradually organises her sensations and actions into a stable concept, toy animal. The representation acquires a permanence lacking in the individual experiences of the object, which are constantly changing. Because the representation is stable, the child “knows”, or at least believes, that toy animal exists even if the actual toy animal is temporarily out of sight.
Piaget called this sense of stability object permanence, a belief that objects exist whether or not they are actually present. It is a major achievement of sensorimotor development, and marks a qualitative transformation in how older infants (24 months) think about experience compared to younger infants (6 months).
During much of infancy, of course, a child can only barely talk, so sensorimotor development initially happens without the support of language. It might therefore seem hard to know what infants are thinking, but Piaget devised several simple, but clever experiments to get around their lack of language, and that suggest that infants do indeed represent objects even without being able to talk (Piaget, 1952).
In one, for example, he simply hid an object (like a toy animal) under a blanket. He found that doing so consistently prompts older infants (18-24 months) to search for the object, but fails to prompt younger infants (less than six months) to do so. “Something” motivates the search by the older infant even without the benefit of much language, and the “something” is presumed to be a permanent concept or representation of the object.