Jean Piaget (1896-1980) was a biologist and developmental psychologist who studied the cognitive development of children. His theories have been influential within the developmental psychology field, as well as in education. Piaget described four stages of cognitive development from infancy to adulthood, including elements such as language, memory, imagination, and thought. Piaget theorized that children gain specific intellectual abilities and a greater capacity for complex understanding during each stage.

Sensorimotor Stage

Infants learn basic motor skills during the sensorimotor stage.
Infants learn basic motor skills during the sensorimotor stage.

The sensorimotor stage lasts from birth until approximately two years of age, and is divided into six sub-stages. Development is focused on motor skills. The infant gains basic reflexes, and begins repetitive activities and habits. The child is also focused on external objects, physical interactions, and experiences. Experimentation and trial-and-error allow the child to acquire basic hand-eye coordination. Increased mobility enhances the ability to explore, leading to new areas of cognitive development. Early language development also begins during the sensorimotor stage.

Preoperational Stage

Young children develop considerable language skills during the preoperational stage.
Young children develop considerable language skills during the preoperational stage.

The preoperational stage generally occurs as the child becomes a toddler, until early childhood (around seven years of age). During this stage, reasoning starts to emerge. The preoperational stage is one of intense language learning. The child also becomes able to represent objects with symbols, and can conceptualize people, events, and places that are not immediately present. Imagination is a large component of this stage, including playing that involves make-believe. The child is still essentially egocentric, and has trouble understanding time and cause-and-effect relationships.

Concrete Operational Stage

Older children gain capacity for logic during the concrete operational stage.
Older children gain capacity for logic during the concrete operational stage.

The concrete operational stage generally occurs between the ages of seven and 11. The child begins to use logic, and to better understand cause-and-effect relationships. The child also gains an understanding of classification. During the concrete stage, egocentricism gives way to an ability to view things from the perspective of others. There is greater awareness of the outside world, and the ability to interpret it in rational ways. The child still has some difficulty understanding abstract concepts.

Formal Operational Stage

The stage between adolescence and adulthood is one of increasingly sophisticated and abstract thinking.
The stage between adolescence and adulthood is one of increasingly sophisticated and abstract thinking.

The formal operational stage lasts from adolescence until early adulthood. During this period, the individual gains increasing ability to think abstractly. Logical reasoning becomes more sophisticated. Adolescents gain abilities to plan more effectively, and systematically test hypotheses. The individual becomes more able to use hypothetical and deductive reasoning, and to follow a process for problem-solving. The adolescent can also gain abilities to formulate complicated verbal arguments, and to understand complex mathematics.