Jean Piaget (1896-1980), a Swiss psychologist, is best known for his pioneering work on the development of intelligence in children. His studies have had a major impact on the fields of psychology and education. Piaget was the first to conduct systematic observations of children in order to study cognition. Piaget was primarily interested in the nature of knowledge and how it could be seen as a form of adaptation to the environment. He described his work as genetic epistemology – the study of the origins and development of knowledge. Piaget based many of his ideas on observations of his own children–Jacqueline, Lucienne, and Laurent. From his observations of children, Piaget concluded that children were actively constructing their own knowledge; they were not limited to receiving knowledge from caregivers or teachers.

In studying the cognitive development of children and adolescents, Piaget identified four major stages: sensorimotor, preoperational, concrete operational, and formal operational. In each stage, children demonstrate new intellectual abilities and increasingly complex understanding of the world. According to Piaget, these stages cannot be skipped—cognitive development always follows this precise sequence. The ages at which children progress through the stages are approximations, varying with the environment and background of individual children. Further, at any given time, a child may exhibit behaviors characteristic of more than one stage. Piaget’s work provides the foundation on which constructivist theories are based. Constructivists believe that knowledge is individually constructed and that each person constructs their own understanding of concepts, which may vary from person to person (Berk, 2017; Crain, 2011; Santrock, 2013.

Sensorimotor Development

In the Sensorimotor Stage, occurring from birth to age 2, the child is concerned with gaining motor control and learning about physical objects. Piaget proposed that an infant’s intelligence is essentially practical in that all interactions with its environment are either sensory (i.e., seeing, hearing, etc.) or motor (i.e., grasping, pulling, etc.). Thus, the first stage of development is known as the sensorimotor stage. Knowledge is limited in this stage because it is based on physical interactions and experiences. Infants cannot predict reactions, and, therefore, must constantly experiment and learn through trial and error. Such exploration might include shaking a rattle or putting objects in the mouth. As they become more mobile, infants’ ability to develop cognitively increases, and early language development begins during this stage.

Preoperational Development

In the Preoperational Stage, from ages 2 to 7, the child is preoccupied with verbal skills. At this point, the child can name objects and reason intuitively. In this stage, children can use symbols to represent words, images, and ideas, demonstrated by children in this stage by engaging in pretend play. A child’s arms might become airplane wings as he zooms around the room, or a child with a stick might become a brave knight with a sword. Children also begin to use language in the preoperational stage, but they cannot understand adult logic or mentally manipulate information (the term operational refers to logical manipulation of information, so children at this stage are pre-operational). Children’s logic is based on their own personal knowledge of the world so far, rather than on conventional knowledge. More complex concepts, such as cause and effect relationships, have not been learned. During this stage, we also expect children to display egocentrism, which means that the child is not able to take the perspective of others. A child at this stage thinks that everyone sees, thinks, and feels just as they do.

Concrete Operational Development

In the Concrete Operational Stage, from ages 7 to 11, the child begins to deal with abstract concepts such as numbers and relationships. In this stage, children can think logically about real (concrete) events; they have a firm grasp on the use of numbers and start to employ memory strategies. They can perform mathematical operations and understand transformations, such as addition is the opposite of subtraction, and multiplication is the opposite of division. Thinking at this stage becomes less egocentric, and children come to understand the concept of conservation—even if something changes shape, its mass, volume, and number stay the same. For example, if you pour water from a tall, thin glass into a short, fat glass, you still have the same amount of water.

Formal Operational Development

The period from adolescence through adulthood is the Formal Operational Stage. During this stage, adolescents and adults begin to reason logically and systematically. Adolescents and adults in this stage are able to use symbols related to abstract concepts. Adolescents can think about multiple variables in systematic ways, can formulate hypotheses, and think about abstract relationships and concepts.  Piaget believed that intellectual development was a lifelong process, but that when formal operational thought was attained, no new structures were needed. Intellectual development in adults involves developing more complex thoughts through the addition of knowledge (Berk, 2017; Crain, 2011; Santrock, 2013).

“Play is the work of childhood.” – Jean Piaget

Criticisms of Piaget’s Cognitive Development Theory

As with other major contributors to theories of development, several of Piaget’s ideas have come under criticism based on the results of further research. For example, several contemporary studies support a model of development that is more continuous than Piaget’s discrete stages (Courage & Howe, 2002). Many others suggest that children reach cognitive milestones earlier than Piaget describes. Piaget’s theory also predicts that thinking within a particular stage would be similar across tasks. In other words, preschool children should perform at the preoperational level in all cognitive tasks. Research has shown diversity in children’s thinking across cognitive tasks. Researchers now believe that children may be more competent than Piaget originally thought, especially in their practical knowledge.

Lastly, according to Piaget, the highest level of cognitive development is formal operational thought, which develops between 11 and 20 years old. However, many developmental psychologists disagree with Piaget, suggesting a fifth stage of cognitive development, known as the postformal stage (Commons & Bresette, 2006). In postformal thinking, decisions are made based on situations and circumstances, and logic is integrated with emotion as adults develop principles that depend on contexts. One way that we can see the difference between an adult in postformal thought and an adolescent in formal operations is in terms of how they handle emotionally- charged issues.

Educational Implications

An important implication of Piaget’s theory is the adaptation of instruction to the learner’s developmental level. The content of instruction needs to be consistent with the developmental level of the learner. The teacher’s role is to facilitate learning by providing a variety of experiences. Opportunities that allow students of differing cognitive levels to work together often encourage less mature students to advance to a more mature understanding. Perhaps the most significant implication for instruction is the use of concrete “hands-on” experiences to help children learn.