Psychology 101: Intro to Psychology

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How does a child's thinking change as she gets older? When does she learn about object permanence, conservation and abstract reasoning? You'll see that thought processes we take for granted as adult are actually important milestones in a child's cognitive development.

Janie is six, and she has really curly hair. She's noticed that when she takes a bath and her hair gets wet, it looks longer. She thinks this is really cool; she believes that her hair literally grows when it gets wet and shrinks again upon drying. She asks her mother one day if keeping her hair wet for longer will help it stay long when it dries; her mother laughs and explains to a disappointed Janie that when curly hair gets wet, it straightens out and looks longer. Hair doesn't actually grow when it's wet. Janie has trouble understanding this, because she's at a stage of cognitive development where it's hard for her to imagine that the same volume of a substance--in this case, her hair--can be shaped very differently. Psychologist Jean Piaget did a lot of work to define these stages, developing his 4-stage model of cognitive development. As children move through these stages, they begin to think more and more like adults.

The first stage, which lasts until the child is about two years old (0-2), is called the sensorimotor stage. Babies in this stage learn about the world through their senses. Cognitively, a baby's biggest sensorimotor development is a sense of object permanence. Have you ever wondered why young babies enjoy peek-a-boo so much? It's not that fun for adults because we know that when a person covers their face, they're still there. But young babies think that if they can't see something, it has disappeared; so when mom covers her face, the baby thinks it's gone, and when she reappears, she's returned! Once babies develop object permanence, at around eight months, they recognize that their mother doesn't really go anywhere, and aren't quite as interested in peek-a-boo.

Piaget's second stage spans ages 2-7. He called it the preoperational stage. Piaget uses operational as a loose synonym for logic. Children in the preoperational stage, therefore, are only in the initial stages of using language and applying abstract thought. They are still not very good at reasoning and going through tasks solely in their heads. Children in this stage are also very egocentric and are gradually learning that others think differently than they do. In experiments to test this, a psychologist will let a child watch him open up an empty juice box, fill it with colorful ribbons, and then seal up the box. Then the psychologist asks what the child's mom will think is in the box. Children at the early end of this stage, around three or four, will say that their mom will know there are ribbons in the box. Only children who are at the later end of this stage will realize that since their mom hasn't seen the psychologist tamper with the juice box, their mom will still think it has juice in it.

Piaget called his third stage, which he believe characterized children from 7-11 years old the concrete operational. Children become more capable of thinking logically during these years. They acquire the cognitive skill that Piaget called conservation, which will eventually help Janie understand that her hair does not actually grow longer when it gets wet. Basically, conservation is the understanding that simply changing the outer form of something does not necessarily change its quantity. To use a more concrete example than Janie's hair, after children have acquired conservation they come to understand that a taller, thinner glass can hold the same amount of water as a fatter, shorter one.

So far we've covered the sensorimotor, the preoperational, and the concrete operational stages. Piaget's final stage, from 11 or 12 years and beyond, is called the formal operational stage. The major accomplishment acquired at this stage is abstract reasoning. Children and adults at this stage are able to think through problems scientifically, rather than by basic trial-and-error. They understand that things in the world aren't black and white and think more about values and goals. They are able to reason through things that are not concrete.

Piaget's stages of cognitive development have shaped the way in which we think about children's cognition, even though subsequent studies have shown that the path to adult thinking is often more complicated than Piaget suggested. Children can acquire new cognitive skills at different times and revert to previous states of thinking, whereas Piaget believed his stages were universal and progressed from start to finish with no backtracking. Subsequent work has also indicated that nurture, or the social environment in which a child develops, is perhaps more important than Piaget had allowed for a child's cognitive development.

Let's quickly summarize Piaget's four stages of cognitive development. During the sensorimotor stage, babies younger than two years old move about their world and explore it with their senses. The preoperational stage comes next, and lasts until about age seven. Children in this stage are egocentric and aren't good at thinking problems through in their heads. The concrete operational stage lasts until around age 11. During this time children develop a sense of conservation, or understanding that changing the outer form of something does not necessarily change internal content. Finally, during the formal operational stage, children learn to apply abstract reasoning.