The Preoperational stage is the second of four stages of cognitive development theorized in Piaget's theory. By observing sequences of play, Piaget was able to demonstrate that towards the end of the second year a qualitatively quite new kind of psychological functioning occurs. Operation in Piagetian theory is any procedure for mentally acting on objects.

According to Piaget, the Sensorimotor stage of development is followed by this stage (2-7 years), which includes the following processes:

Symbolic functioning - is characterised by the use of mental symbols words or pictures which the child uses to represent something which is not physically present.

Concentration - is indicated by a child concentrating more on one aspect of a person which is consistent rather than concentrating on the inconsistent aspects of his personality,behaviour or physical characteristics.

Intuitive thought - occurs when the child is able to believe in something without knowing why she or he believes it.

Inability to Conserve -Through Piaget's conservation experiments (conservation of mass, volume and number) Piaget concluded that children in the preoperational stage will not be able to conserve mass, volume or number after the original form has changed.

The next stage in Piaget's theory of cognitive development is the Concrete Operational stage.