Which psychologist thought that development occurred in stages?

Jean Piaget

Explanation:

The theory developed by Piaget conceives a model of development where 4 main stages take place.: the sensorimotor, preoperational, concrete operational and formal operational period.

The model implies that children gradually construct knowledge first through direct sensations and experiencing to gradually move to concrete and formal thinking. The stages also imply how intelligence develops and may suggest why sometimes hindering a stage can have important consequences in later life of anyone.

His theories are still so widely used, and many educational and psychological approaches draw on may of his assumptions