ConfidencePiaget described development in terms of successive changes in how children think. He suggested that they come through three periods of development, each distinguished by a different way of thinking.


Age Period of Development Cognitive Structures
Birth to 2 Years Sensorimotor Infants understand the world through perception and action. Abilities expand throughout this period, so that by age two, toddlers can purposefully combine their actions.
2 to 11 Years Concrete Preoperational Subperiod Children master independently acquired skills. Children are able to form mental representations of objects and imagine actions related to them. Thought is egocentric (self-centred).
7 to 11 Years Concrete Operational Subperiod Children are capable of logical thinking. Their imaginations are constrained by reality, and they can perform logical operations on concrete objects.
12 Years Through Adulthood Formal Operational Children develop the ability to reason abstractly.


According to Piaget, cognitive development through adolescence involves:

  • movement from concrete to abstract thinking, and
  • a decrease in egocentric thought.

Prior to adolescence, the thinking of a child is concrete. The acquisition of formal reasoning skills allows older adolescents (age 15 onwards) to think about many possible outcomes of a situation that do not exist now. They can construct possibilities and assess probabilities. Imagine, for instance, that you pose the hypothetical situation of an adolescent pregnancy. An adolescent with formal reasoning skills (with appropriate guidance) could try to think through the full implications of parenting a new-born.

The transition from concrete to completed formal operational thinking occurs in stages between the ages of 11-14. According to Piaget and other cognitive theorists, the predominance of egocentric thought during this period leads to some particular views and behaviours, including:

  • self-consciousness
  • the imaginary audience: feeling as though one’s actions and appearance is being constantly scrutinized
  • the personal fable: viewing one’s thoughts and feelings as unique experiences, and
  • feelings of invulnerability, leading to risk-taking behaviour.

By sharing experiences with peers, adolescents learn that many of their thoughts and feelings are shared by almost everyone. This realisation helps them to feel less unique — or less “abnormal” — and more like others. The egocentric thinking of early adolescence therefore lessens by the age of 15 or