Jean Piaget is perhaps one of the most influential developmental psychologists of the 20th century. His most significant theory is that humans develop through a series of four stages that roughly map onto key stages.
Piaget emphasized the importance of interaction between physical environmental and maturational factors in development. He developed a theory of cognitive development largely from the observation of children. Through this observation, he observed four distinct stages that children go through in their development. Piaget theorized that children must become proficient in each stage in order to progress to the next.¹
Piaget believed that our progression through these four stages is marked by a building and rebuilding of schemata through cyclic processes known as mechanisms for development:¹
Assimilation is the process by which new information about the world is incorporated into existing schema*. This does not require any need to revise the scope of that schema.
Accommodation is the process by which existing schemata are modified or changed by new experiences. As a result, we must either slightly adjust the parameters of the schema or believe that the new information is an exception to a rule.
Equilibrium is the process that occurs when we accommodate information to the point where the original schema no longer holds true and we must form entirely new schemata.
*Schema is a mental framework through which we can organize, synthesize and understand information about our surroundings.
One of the most prevalent criticisms of Piaget’s stage theory is that it does not account for variability in child development. For example, other researchers have demonstrated that the ability to solve conservation tasks vary across individuals by several years. Modern research techniques have demonstrated that cognitive capacities of infants is most likely far greater than Piaget theorized. Some also criticize Piaget for focusing too much on one’s physical environment and not enough on their social environment.
Despite these valid criticisms, it is undoubtable that Piaget made leaps and bounds in the field of Developmental Psychology. Later theorists such as Lev Vygotsky used Piaget’s material to build more nuanced theories.
The following are Piaget's four life stages:¹
- Sensimotor Stage
- Preoperational Stage
- Concrete Operational Stage
- Formal Operational Stage