The Sensory-Motor Period (0-18 months)

Piaget labeled the first stage of cognitive development, that of a newborn, the sensory-motor period. It lasts from birth to about 18 months of age. At first (Piaget believed) the infant is unable to differentiate itself from the environment. In the first months of life it comes to recognize the existence of people and things separate from itself. Babies developed intentionality (goal-directed behavior) during the sensory-motor stage. They learn to execute simple goal-directed plans, such as reaching out and grasping a pacifier.

What are characteristics of the sensory-motor period, in Piaget's scheme? What is object constancy?

Piaget pointed out a phenomenon that surprised people at first. Infants act as though a hidden object ceases to exist. To very young children—younger than about 6 months—"out of sight" is not only "out of mind" but also "out of existence." If a toy eagerly pursued by a 4 month old slips under a blanket, it is no longer pursued...even if it makes an obvious bump. A tyke about three months old loses interest in a toy once it is hidden behind a curtain. Piaget said such a child lacks object constancy, the awareness that a hidden object continues to exist.

By the age of one, a baby will brush a blanket aside and attempt to locate a toy hidden there. This shows the baby knows the hidden object continues to exist. The baby now has a mental representation of the object: a mental structure or schema. This developmental sequence is basic and primitive, and there is no reason to expect it would be limited to humans. Indeed, Wise, Wise and Zimmermann (1974) showed that the infant rhesus monkey goes through a very similar succession of stages.


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Copyright © 2007 Russ Dewey