Sensorimotor Substage: Object Permanence:
Substage 1 (0 - 1 1/2 months)

Reflex Schemas

Involuntary responses to stimuli; e.g. sucking

Makes no attempt to locate objects that have disappeared
Substage 2 (1 1/2 - 4 months)

Primary Circular Reactions

Attempts to repeat chance pleasurable actions, on or near the body; e.g. bringing thumb to mouth

Still makes no attempt to locate objects that have disappeared
Substage 3 (4 - 8 months)

Secondary Circular Reactions

Attempts to repeat chance pleasurable actions, in the environment; e.g. hitting a mobile; picking up a cup

Searches for objects that have dropped from view or a partially hidden
Substage 4 (8 - 12 months)

Coordinated Secondary Circular Reactions

Can put 'secondary circular reactions' together to solve new problems; e.g. uncover, then grasp

Searches for completely hidden objects--but makes the A-not-B error
Substage 5 (12 - 18 months)

Tertiary Circular Reactions

Will deliberately vary an action pattern, to discover the consequences; e.g. dropping ball from different heights

Now has the ability to follow visible displacements of an object
Substage 6 (18 - 24 months)

Beginnings of Symbolic Representation

Can solve problems using representation; e.g. opening and closing mouth

Now has the ability to follow invisible displacements of an object