Most fields of psychology have one or more developmental theories, meant to explain how people develop their personalities and abilities. The major theory of development in cognitive psychology was formulated by Jean Piaget, and has been very influential in many areas including education. Piaget suggested that we each progress through four stages as we develop the ability to think maturely, and that we suffer from certain illogical thought patterns in the first three stages. There have been several criticisms of this theory, including that its ages are too generous and that it doesn’t account for individual differences, but its general ideas are sound.
Sensorimotor Period: From birth to about 2 years, we explore and learn about the world through our senses. The main difficulty Piaget identified with this stage is the lack of object permanence, the understanding that objects are still there even when removed from sight. If you show a baby a toy and then cover the toy with a blanket, the baby will likely lose all interest because it has forgotten the toy even exists.
Preoperational Period: We are in this stage 2 to 7 years, and now can think about objects that aren’t there. We can form mental representations: thoughts about things we can’t currently see or touch. Preoperational children have a number of limitations in their thought, however. These include egocentrism, an inability to understand that other people have their own unique thoughts; conservation, not understanding that objects that change their shape don’t also change their mass; and animistic thinking, or imagining that inanimate objects have thoughts and feelings like people do.
Concrete Operations Period: Children from 7 to 11 years old can think more logically and problem solve, but have difficulty thinking hypothetically and abstractly. They reason best when they have physical objects to manipulate and help them think, such as blocks.
Formal Operations Period: From 12 years up, Piaget said we can think in formal and adult-like ways. Youngsters at this stage can now reason hypothetically and abstractly, answering complex ‘what if’ problems and imagining possible benefits and drawbacks to a future decision.