Among child psychologists who have attempted to track the dramatic shifts in cognition, knowledge, and memory that distinguish infants from adults, Jean Piaget has had the greatest inﬂuence. Based on intensive observations of a small sample of infants, including his own children, as well as extensive interviews with older children, the Swiss psychologist proposed a theory in which developmental change is qualitative rather than merely quantitative. In other words, an older child thinks differently than an infant, and a teenager thinks differently than an older child, and an adult thinks differently than all of them. Children don’t just know less, remember less, and have less experience than adults, they actually think in completely different ways at different ages. Jean Piaget’s developmental theory, which he referred to as genetic epistemology, proposes that cognitive development proceeds through a series of distinct stages, or periods, and that all children pass through the same stages, in the same order, in a universal and invariant sequence. The start of each stage is marked by a qualitative change from what preceded it.
So what changes from stage to stage? Piaget saw the mind as made up of cognitive structures he called schemas, which are mental images or generalizations based on our experience of the world. We use schemas both to organize past experience and to provide a framework for organizing and understanding future experiences. The newborn infant has very little experience, thus very few schemas. Piaget saw infant reﬂexes, such as the sucking reﬂex, which allows the newborn to feed immediately, as the earliest schemas. The infant immediately begins gaining experience with the outside world, however, which causes the schemas to begin changing almost at once. The sucking schema will rapidly change to accommodate the fact that a range of objects may be sucked, but not all sucking will produce food, for example.
Two processes guide the development of ever more complex schemas: assimilation and accommodation. Assimilation is the process by which new information is placed into existing schemas. A child who has a cat at home, for example, will have no difﬁculty recognizing the nature of a new cat since the child already has a schema for what a cat is. Real cognitive change, however, comes from the challenges to our existing schemas that the world is always ready to provide. This process is known as accommodation. For example, when that same child encounters his or her ﬁrst dog, the child will ﬁrst try to ﬁt this new creature into what is already known (“Kitty?” he or she says tentatively). Fairly brief experience will show that this creature doesn’t ﬁt the schema, however, and so the schemas must change to reﬂect the new state of the world. A new “doggie” schema, along with a more general “pet” or “animal” schema may be the result.
Piaget called the ﬁrst stage of cognitive development, from birth to about age two, the sensorimotor period, as the child’s development in this stage is largely conﬁned to schemas about sensory functions and motor skills. Piaget believed that during this stage, infants can form schemas only about objects and actions that are actually present. If an object is not currently in sight or within grasp, the child cannot think about it. He based this belief largely on the observation that if an adult covers or hides a toy that the infant is currently reaching for, the child will immediately appear to lose all interest in the toy, without trying to ﬁnd it. For the infant, out of sight is out of mind. The sensorimotor period ends when the child is able to form mental representations of objects despite being unable to see them, an ability Piaget called object permanence.
From about age two to around age seven, children are in the preoperational stage, in which they can think in images and symbols, able to represent something with something else. Unsurprisingly, this is the stage in which language use and pretend play become common. Piaget believed that children at this stage are highly egocentric, meaning they are unable to appreciate the perspectives of others or understand that there is any way to see a situation other than their own. He based this belief on a task in which the child walks around a three-dimensional model of three mountains and is then asked what someone (usually a doll) would see from a particular position. Preoperational children typically select the view that corresponds to their own current perspective, rather than the correct one. The name of the stage, however, comes from children’s performance on tasks requiring conservation: recognition that important properties of a substance remain constant despite changes in shape or appearance. In the classic test of conservation, children watch as water or juice from two identical glasses is poured into two new glasses, one tall and thin and the other short and wide. When asked if one glass contains more than the other, preoperational children typically choose the taller glass. Children at this stage do not understand the mental operations of reversibility (if they poured the water back into the original glasses, they would clearly hold the same amount again) and complementarity (one glass is taller, but the other makes up for that difference by being wider), thus their thinking is preoperational.
In the concrete operations stage, ages seven to about twelve, the child becomes able to understand and apply logical principles, thus conservation is no longer a challenge, and the ability to apply such logic to number and amount makes mathematics learning possible. According to Piaget, however, the child’s ability to perform logical operations is limited to real, concrete objects within their experience. The ability to think logically about abstract ideas awaits the development of formal operations, the developmental period that begins with adolescence, and the ﬁnal stage proposed by Piaget. The fact that Piaget’s developmental sequence ends with adolescence has prompted other theorists to propose several variations on an additional stage of post formal reasoning, to allow for recognition that the adult mind often works differently than that of a twelve-year-old child.
The basic elements of Piaget’s theory remain very inﬂuential today, especially the insight that adult thinking differs qualitatively from that of young children, along with the recognition that various cognitive milestones are achieved in the same order by all children. Piaget has also been widely criticized, however, especially for underestimating the cognitive abilities of young children by frequently using tasks that the children didn’t understand. A large body of research on infant memory, for example, indicates that children are capable of using mental representations at much younger ages than Piaget believed.
Conservation may also appear a lot earlier than Piaget suggested, an insight that requires altering Piaget’s favorite tasks a bit. When the children do the pouring in the liquid conservation task, rather than watching an adult do it, preoperational children frequently answer correctly. Preoperational children are also less egocentric than Piaget imagined, as when the three-mountain task is redesigned a bit to more closely resemble a game children might actually play. Instead of mountains, children look in on a simple maze in which some walls contain windows and some don’t. A doll dressed as a policeman is then placed in the model, as is a doll dressed as a thief. Children are asked to take the perspective of the policeman and decide whether he can see, and therefore catch, the thief. Preoperational children answer correctly at much higher rates than they did on Piaget’s task, perhaps because the task is more relevant to the children’s experience.
Furthermore, many psychologists question the wisdom of thinking in terms of rigidly bounded stages, rather than recognizing that children reach some concrete-operational milestones before others. It makes more sense, therefore, to think in terms of individual mental abilities developing rather the whole mind changing at once. Still, Piaget continues to cast a large shadow on the ﬁeld of study that he created.
- Donaldson, Margaret. Children’s Minds. New York: W. W. Norton & Co., 1979.