Was the most influential theorist on cognitive development and may be considered the most important developmental theorist of all time?

One of the most popular theories of cognitive development was created by Jean Piaget, a Swiss psychologist who believed that cognitive growth occurred in stages. Piaget studied children through to their teens in an effort to determine how they developed logical thinking. He attempted to document the stages of cognitive development by observing the memory processes of children.

Was the most influential theorist on cognitive development and may be considered the most important developmental theorist of all time?
Jean Piaget

Essentially, Piaget believed that humans create their own understanding of the world. In theological terms, he was a psychological constructivist, believing that learning is caused by the blend of two processes: assimilation and accommodation. Children first reflect on their prior experiences to understand a new concept and then adjust their expectations to include the new experience. This means that children are continuously constructing knowledge based on the newly presented ideas, which lead to long-term changes. Piaget was more focused on the cognitive developments presented over time.


Through his studies, Piaget declared that cognitive development occurred in four stages throughout one’s childhood:

  1. Stages occur in order.
  2. Children did not skip stages but pass through each one.
  3. There are visible changes from one stage to the next.
  4. The stages occur as building blocks, each one using pieces from the last stage.
Was the most influential theorist on cognitive development and may be considered the most important developmental theorist of all time?
Stages of Cognitive Development

This type of developmental model incorporates each stage into the next, which is why it is often called a “staircase” model. On this staircase, Piaget labeled four stages of cognitive growth that occurred at an approximate age in children.

  1. Sensorimotor Intelligence, from birth to age 2.
  2. Preoperational Thinking, from ages 2 to 7.
  3. Concrete Operational Thinking, from ages 7 to 11.
  4. Formal Operational Thinking, from age 11 on.

The Sensorimotor Stage: Birth to Age 2

The first stage is aptly named after how infants learn until age two. From birth, infants absorb information through their senses: by touching, looking, and listening. They are very orally fixated and tend to put everything in their mouths. Piaget believed that this stage was valuable to their development, and each consecutive step is built on the growth that occurs in this stage.

We can observe the thought processes of infants through their actions. From about 6 months on, children begin to organize ideas into firm concepts that do not change. An infant may first not make sense of a specific toy, but as they begin to look at it, feel it, and manipulate it often, they are able to represent the object in their minds. This is how we can begin to observe knowledge in babies, as they begin to show understanding of an object for what it is. For example, by playing continuously with a toy animal, an infant begins to understand what the object is and recall their experiences associated with that toy. Piaget labeled this understanding as object permanence, which indicates the knowledge of the toy even if it is out of sight. He considered this understanding to be a major milestone in the sensorimotor stage and believed that it demonstrated the differences in the thought processes of toddlers compared to young infants.

The sensorimotor stage is unique in that is occurs without the use of language. As infants cannot speak, Piaget developed a few creative experiments in an effort to understand what they were thinking. His experiments were able to demonstrate that infants do represent objects and understand that they are permanent. In one of his experiments, Piaget consistently hid a toy underneath a blanket. Toddlers, or children between the ages of 18 and 24 months, took initiative to look for the toy themselves, but infants less than 6 months of age did not. The older infants interpreted the hiding of the toy as a prompt to search for it, which is thought to support the idea of object permanency.

The Preoperational Stage: Age 2 to 7

Children continue to build on the object representation that is significant to the sensorimotor stage in different activities. While the way they represent objects has no logic or reasoning behind it, they continue to grow in this area through dramatic play. Imaginative play, or the art of make-believe, is an indicative sign of this age and stage.

As dramatic play is considered to be beneficial to educational growth, teachers often promote its use in the classroom. The preoperational stage occurs from age two to age seven, which means that imaginative activities are encouraged from preschool all the way to second grade. Dramatic play is considered to be one of the first demonstrations of metacognition in children, or dual thinking. While engaged in imaginative play, children are simultaneously reflecting on the realistic experience.

The Concrete Operational Stage: Age 7 to 11

In Piaget’s next stage, children begin to represent objects and ideas in a more logical way. While the thought process is not on the same level as an adult, they begin to be more flexible in their thoughts and ideas. This allows them to solve problems in a more systematic way, leading to more success in educational activities in school. Piaget labeled this stage as concrete operational because he believed that children were able to manage concrete objects, but not yet think methodically about the representations of objects. It is only later that children are able to reflect on abstract events and manipulate representations of events. For example, a child may implement the rule “if nothing is added or taken away, then the amount of something stays the same.” Applying systemic rules or ideas may help a child solve simple tasks in the classroom, such as addition and subtraction problems or scientific calculations.

There are two things that distinguish concrete operational thinking from preoperational thinking. The first is reversibility, which allows a child to manipulate the order of any process. We can use the example of a sink or float science experiment to demonstrate the presence of reversibility. In this experiment, the child places various objects in a bucket of water, testing to see if they float or sink. A child in the preoperational stage would be able to describe the procedure taken, but only a child in the concrete operational stage would be able to retell the experiment in various ways, such as chronologically or out of order. Multi-step procedures are common in the classroom setting, which makes reversibility a valuable skill in learning. Children that are still in the preoperational stage may require assistance in activities in the form of prompts or reminders from the teacher. We can use the task of learning vocabulary from a story as an example in the classroom. The teacher may assign a multi-step instruction to the students: first, write down the words you don’t know as you come across them in the story, second, search for the definition before continuing on with the story, and third, have a friend quiz you on all of the words that you just learned. This type of multi-step instruction involves returning to the first and second tasks many times, which only children who have already reached the concrete operational stage are able to do.

The second skill that is acquired is decentering. This allows the child to step back and analyze an issue from more than one angle. Being able to consider a problem from another perspective is a key feature of the concrete operational stage. We can view the emergence of this ability in the preoperational stage when children start participating in dramatic play. For example, a child may use a banana as a pretend telephone, demonstrating an awareness that the banana is both a banana and a telephone. Piaget argued that children in the concrete operational stage are making more intentional and calculated choices, illustrating that they are conscious of their decentering. An example in the classroom can be displayed in the form of a simple worksheet. Using a multi-step instruction, the teacher can ask students to identify all problems that fit two criteria: it is a two-digit subtraction problem and it requires regrouping. The child is only responsible for solving problems that fit both of those requirements. A child in the concrete operational stage can move between the first and second criteria with ease, analyzing each problem to see if it meets both specifications. This task would also assume that the student is already able to regroup subtraction problems independently.

Both reversibility and decentering tend to occur together in educational settings. As seen in the worksheet example, procedures may occur out of order while multiple criteria are in place. Piaget had a popular example to demonstrate the idea of conservation or the idea that a quantity will remain the same despite the shape. He used two similar size balls of clay for his experiment. While a child in the preoperational stage may attest that the two balls of clay “look the same,” they are basing their assumptions purely on external observations. If one ball of clay were stretched thin like a hot dog, a child in the preoperational stage may state that they are different, even if the shape used the same amount of clay. In the concrete operational stage, a child is able to understand that two different shapes can be made from the same volume of clay. The child may provide reasoning for his answer using reversibility, stating that “you could squish it back into a ball again,” or decentering, as “it may be longer, but it is thinner.” Piaget maintained that children in this stage could demonstrate conservation of quantities despite the shape.

The Formal Operational Stage: Age 11 and Beyond

As children move into the formal operational stage, they are able to reason about more abstract ideas. Much like the concrete operational stage, the formal operational stage gets its name from the newly acquired skill of representing objects or events. In class, a teacher is now able to ask hypothetical questions with reasonable expectations. Students must reflect internally on various ideas and manipulate many perspectives at once. “What if the world had never discovered electricity?” “What if the European settlers had never left for the New World?” Abstract questions such as these force students to use hypothetical reasoning to come up with an answer.

Piaget was most interested in hypothetical reasoning in scientific experiments, which resulted in most of his studies being conducted at the middle and high school levels. In one study, students are asked questions about a pendulum, a pivot from which weights are freely suspended. “What determines how fast the pendulum swings: the length of a string holding it, the weight attached to it, or the distance that it is pulled to the side?”

Students in Piaget’s experiments were not allowed to physically solve the problem by manipulating the pendulum but were asked to orally reason a solution. This meant that individuals were forced to imagine all of the factors independently while taking into account the factors that remained constant. Being able to resolve this problem in a systemic way was a clear determinant of formal operations in the thought process. The ability to manipulate various outcomes is the precise skill of the formal operational stage.

There are clear advantages for students who have already achieved the formal operational stage. They require far fewer supports in solving problems, which allows them to be more independent in educational settings and need less direction from their teachers. However, this does not mean that they are able to successfully complete all academic tasks nor is it the only way to do so. Self-regulation remains an important part of academic success; if a student is lacking self-motivation or is not well behaved, they do not do as well in school. Formal operational thinking does not offer specialized skills either, such as musical and artistic talent or athletic greatness. One critique of Piaget’s theory is that this stage only covered scientific problem-solving in educational settings, which most people do not come across in their everyday lives. As such, many never achieve this level of operational thinking, or if they do, they use it only inexperienced and familiar situations. This proves that more research is needed on the development of personal and interactive issues of children and youth.