Jean Piaget - Developmental Psychology - The Canon

Psychology: Essential Thinkers, Classic Theories, and How They Inform Your World - Andrea Bonior 2016

Jean Piaget
Developmental Psychology
The Canon


BORN 1896, Neuchâtel, Switzerland


DIED 1980, Geneva, Switzerland


Educated at the University of Neuchâtel and the University of Zurich



Jean Piaget’s name is known to virtually anyone who takes a scholarly interest in child development, from teachers to therapists to medical doctors. He referred to his area of work on the origins of knowledge as genetic epistemology. (Note that genetic in this sense does not refer to genes and biology but rather to how something emerges and develops.) Piaget’s ideas were a departure from earlier theories of intellectual development, as he felt that intelligence grows qualitatively with age, not just quantitatively. And he insisted that it grows in an active way that depends on a child’s interactions with his or her environment. The latter idea is often said to reflect a constructivist way of thinking.

Schemas, or schemata—the mental structures that we use to make sense of our experiences, and that help us organize our environment by allowing us to categorize our perceptions and knowledge into patterns—are an important building block of Piaget’s work. (Piaget was the first to apply the term schemas in a systematic way to psychology, originally calling them schemes.) Schemas create shortcuts for us, though they can sometimes lead to stereotyping. A schema can be represented by anything from “Cars have four wheels,” to “If I let go of a toy I’m holding, it will fall.” Piaget suggested that there are different types of schemas that depend on one’s stage of development. Babies, for example, can use only behavioral schemas; an object has meaning only if it is in front of a baby who is acting on it. Older children, on the other hand, can conduct cognitive operations with an object, developing schemas that involve more general rules as to its qualities.

Piaget proposed that, over time, children learn to adjust their schemas, not just through combining them but also through adapting them to their environments. This process of adaptation entails two complementary aspects: assimilation and accommodation. Assimilation is the attempt to fit the outside world into a schema that the child already has. Let’s say a child has a schema for oranges, knowing that an orange is a round fruit. One day the child is faced with a mandarin orange. It is much smaller than what the child is used to, but it fits the child’s existing schema, so the child now has a new type of orange there. The child is assimilating it into his schema. But let’s say that one day he is faced with a grapefruit. It, too, looks basically like an orange, and so he considers it to be one. But let’s say he tastes it, and—whoa! It is very different from the oranges he knows so well. He must therefore adapt his existing schema to take this new information into account. After hearing the explanation of a grapefruit, he now changes his current schema to encompass the fact that not all round fruits are oranges. This is accommodation. (The fact that grapefruit have nothing in common with grapes will have to be tackled when the child is older.)

Piaget theorized that these processes are what create intellectual growth, and he recognized that cultural and environmental factors can speed up or slow down that growth. But he also argued that growth always unfolds in a particular order, and his best-known theory lays out four sequential stages of that development: the sensorimotor, preoperational, concrete operational, and formal operational stages.

During the sensorimotor stage, as its name implies, a baby is focused on decoding her environment through her senses and beginning to understand how her body can move within her environment. Piaget said this stage begins at birth and starts with the reflexes newborns are equipped with. According to Piaget, over the course of the next two years, an explosion of growth moves the child along from having only reflexes as a tool to actually being able to think about her environment much more critically. There are several substages and much action in these first two years. From the ages of 1 to 4 months, infants start to control their behaviors (for example, cooing and finding their thumbs to suck on). But they are still focused on their own bodies. By 8 months, they are more purposefully interacting with external objects, and by 12 months, they are becoming more intentional, and they’re coordinated enough to lift, to grasp, and to chain behaviors together, moving toward true goal setting. By 18 months, a child will begin to experiment more with objects, learning just what happens when she throws her bowl of soup on the floor. And by 24 months, she is constructing mental images and beginning to think symbolically. She is developing true insight into how to solve problems (or perhaps create new ones for her parents: “If I move that chair up to the kitchen counter, I’ll be able to climb up onto it!”). Throughout the sensorimotor stage, object permanence solidifies. That’s the understanding that objects continue to exist even when the child can’t immediately see or otherwise sense them. This isn’t automatic knowledge upon birth (one reason peekaboo is so thrilling).

The preoperational stage, from about the age of 2 until the age of 7, sees an overwhelming increase in language and representational thought. Early in this period, symbolic play develops: tea parties without real tea, horses that are really broomsticks, and even the presence of imaginary friends. We also see animism at this stage—the attribution of living qualities to inanimate objects (“The clouds are sad, and that’s why it’s raining.”). And Piaget argued that egocentrism is a defining characteristic in the early part of this stage, with the child assuming that others all share his point of view; there’s an inability to draw the line between himself and others. A child exhibiting egocentrism assumed that because he saw his brother take an extra cookie, his mother also knows about the transgression, even if she wasn’t in the room to witness it. Also observed within the beginning of this stage is lack of understanding of the principle of conservation of quantity; a young preoperational child cannot tell that when juice from a tall, skinny glass is poured into a shorter, broader glass, it is still the same amount of juice.

Next is the concrete operational stage. Thought to typically last from about the age of 7 until the age of 11, it is the stage when children become able to solve problems with logic and various other mental strategies that are much more systematic than those they used in the previous stage. A child at this stage can understand the connection between related parts of a series—this is understanding of transitivity—and can mentally arrange items along a scale by degree, as when she mentally lines up her classmates by height (this is called mental seriation).

Finally, starting at about the age of 11 or 12 and continuing until the end of life, comes the formal operational stage. Now abstract thinking becomes possible, and philosophical ideas, hypotheses, and systematic solutions to larger problems take hold. Children and teenagers at this stage will show deductive reasoning—the ability to take general principles and apply them to specific cases. People at this stage can also start to question the world’s structures in abstract ways; it’s why a preteen is able to pick up on political hypocrisy.

Though some of the exact skills and abilities Piaget spelled out for each stage have been refined and challenged in the decades since, and though some theories of intelligence have emerged that look at separate intelligences rather than at wholesale stages of development, Piaget’s name is a blockbuster one because of the exhaustive data he collected and the attention he gave to understanding individual children’s mental processes. He laid the foundation for understanding mental development from birth to adulthood, and his theories are still put to use in many settings.



Decades of study within developmental psychology were directly spurred on by Jean Piaget’s findings and by the new techniques he developed, including individual clinical interviews with children aimed at understanding their mental processes. Piaget’s ideas about the necessity of active learning and the importance of meeting a child where he is developmentally, rather than trying desperately to speed him up to the next stage, still have many followers today.


If you’ve ever tried to talk with a child at Piaget’s concrete operational stage, you may have come face to face with just how concrete she can be—in fact, you may wonder how to handle this when it comes to explaining the world around her. Perhaps she has already internalized that smoking cigarettes is unhealthy or that honesty is the best policy. That is all great, of course, and yet when it comes to the messier nuances of the real world, her mindset may butt up against more complex realities. It can be downright impossible for a child at this stage to think in more abstract terms, and it can lead to some rather awkward situations: “Grandma must be dumb because she smokes,” or “I need to tell the truth—Uncle Justin is getting fat.”

On a lighter note, perhaps you’ve had the misfortune of scooping ice cream into bowls at a 4-year-old’s birthday party. Maybe you gave one child two small scoops and the birthday boy one big one. Watch out! The birthday boy might just launch an all-out mutiny. If he is not yet able to understand the principle of conservation of quantity, he sees his one scoop as woefully inferior to the two scoops given to his buddy.

Another classic Piagetian concept is the A-not-B error, also called the perseverative error. Let’s say you have two boxes (A and B), a toy, and a baby between the ages of 8 and 12 months. If you repeatedly show the baby that you are putting the toy in box A, she will learn to look for it in box A. But then you mix it up—let’s say you show her that you’ve put the toy in box B. She will likely still look for it in box A because that is where she found it previously. Piaget believed that this error persists because of the baby’s behavioral schema. The baby can’t understand that the toy can be put somewhere that has nothing to do with where she last found it. Other arguments have since been developed as to why this error exists, but Piaget was the first to identify it.

We all know people who enjoy certain stages of childrearing more than others. Some people like the snuggly “baby burrito” stage, others the “philosophizing teenager” phase, and still others some stage in between. Have you ever really thought about why this is, however? It’s likely not the child’s ability to walk or drive, or how tall he is. It’s who he is mentally. For every stage of a child’s development, we have a classic snapshot in our heads of what makes that child tick; we fundamentally understand that a 3-year-old, a 6-year-old, a 9-year-old, and a 12-year-old will say and believe very different things. These mental differences are qualitative and meaningful; they’re not just matters of degree. And Piaget was a pioneer in systematically measuring these differences and quantifying them for the world at large.