Concrete Operational Period

The  concrete  operational  period  is  the  third period in Jean Piaget’s theory of cognitive development. Piagetian periods occur in invariant order. Thus, a child must pass through the sensorimotor and preoperational periods before entering the concrete operational period and must pass through the concrete operational period before entering the formal operational  period.  Although  exact  ages  of  acquisition are not central to Piaget’s theory, he proposed that children in the concrete operational period are between the ages of 6 and 12. Contemporary research has found that both younger and older individuals may engage in thought that is characteristic of the concrete operational period.

Each Piagetian period is characterized by qualitative changes in the nature of children’s thought. Entry into the period of concrete operations is marked by the child’s mastery of operations. Operations can be defined as the mental representation of transformations. Using operations, children in the concrete operational period are able to reason logically about real situations. Children in this period are still unable to reason logically about hypothetical situations or to reflect upon their own thoughts.

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Entry into Piagetian periods is marked by success on Piagetian tasks designed to assess the quality of children’s reasoning. Typically, conservation tasks are mastered by children during the concrete operational period. Conservation can be defined as the realization that changes in appearance do not cause changes in quantity. Conservation is tested in the domains of number, length, liquid, mass, area, weight, and volume. In the conservation of mass task, a child is shown two identical balls of clay. The child is asked if the two balls have the same amount of clay. If the child believes that one of the balls contains more clay than the other, adjustments are made until the child believes the two balls have equal amounts. One of the balls is then flattened while the child watches. Again, the child is asked if the two balls have the same amount of clay. Children in the preoperational period believe that the flattened ball has either more or less clay than the rolled ball. Children in the concrete operational period understand three concepts that help them to realize that the amount of clay is unchanged: (1) Identity: An item’s appearance can change without changing its identity. Using identity, the child reasons that only the shape of the clay has changed, not the amount. (2) Reversibility: The effects of actions can be reversed. Using reversibility, the child reasons that because the flattened clay could be rolled into a ball again, the amount has not changed. (3) Decentration: A change in one dimension can be compensated for by an opposite change in another dimension. Using decentration, the child reasons that although the flattened clay covers a wider area, it is also thinner than the rolled clay and that therefore the amount has not changed.

In general, Piaget believed that advances in reasoning are domain general, meaning they occur in all areas of knowledge. However, in the case of conservation, Piaget recognized a decalage. Decalage can be defined as instances in which children show more advanced  forms  of  reasoning  in  one  domain  than in other domains. For example, children typically conserve number, length, liquid, and mass before they conserve area and weight and conserve area and weight before they conserve volume.

When Piaget’s tasks are exactly replicated, his results have been widely validated both cross-culturally and across different cohorts. However, contemporary research has found that children show earlier evidence of identity, reversibility, and decentration when the traditional tasks are simplified.


  1. Beilin, (1992). Piaget’s enduring contribution to developmental psychology. Developmental Psychology, 28, 191–204.
  2. Flavell, H. (1996). Piaget’s Legacy. Psychological Science, 7, 200–203.
  3. Piaget, J. (1970) Piaget’s theory. In P. H. Mussen (Ed.), Carmichael’s  manual   of   child   psychology:   Vol. New York: Wiley.