Stage 1: The Sensorimotor Stage: between 0 and 18 months. Piaget believed that babies learn through their senses and only experince the present, with no memories or thoughts. He claimed that babies ‘reflex activity’ becomes the foundation for all cognitive functioning in the future, through the process of assimilation and accomodation.
Stage 2: The Pre-Operational Stage: between 18 months and 7 years. The major distinction between the sensorimotor stage and the preoperational stage is the degree of development and the use of internal images and symbols (e.g. words) as is marked by the establishment of object permanence.
The child uses symbolic functions, their language development accelerates and imaginative play becomes more apparent as they spend a lot of their time engaged in make-believe.
Another important difference seen in this period is that children can imitate (copy) another’s behaviour after some time has passed, implying that they have a way of symbolically remebering the original behaviour that they observed.
These actions suggest an internal cognitive mediation process between incoming stimuli and later responses.
Stage 3: The Concrete Operational Stage: between 7 and 12 years. Operations are logical rules and it is thought that children in this stage are able to use logical rules to deal with problems.
Stage 4: The Formal Operational Stage: between 12 years and above, when thoughts are governed by logical reasoning and cause and effect can be considered.