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Critically Assess Piaget’s Theory of Cognitive Development

This essay will look at the theory put forward by Jean Piaget (1896-1980) that cognitive development is a process that is defined by stages of thinking which change as a person grows from infancy to adulthood. It will examine his theory, commenting on its strengths and weaknesses and compare it to other cognitive development theories put forward by Jerome Bruner and Lev Vygotsky. Cognitive development is defined as “the development of intelligence, conscious thought, and problem-solving ability that begins in infancy” ( Piaget was interested in how thinking develops in an individual, and he developed his theory after becoming unhappy with the idea that intelligence is a fixed attribute.

Instead, he considered it a process that developed over time due to biological maturation and interaction with the environment. As the brain grows and becomes more intricate, it can develop more complex ways of thinking. However, children are limited to benefit from the experience as their brains are not adequately developed enough. The environment is also linked to cognitive development as children are fundamentally programmed to explore and test the world around them. This is why Piaget called children “little scientists” ( In this way, Piaget is seen to be a constructivist.

According to Piaget, there are four stages of cognitive development, sensorimotor, pre-operational, operational, concrete operational and formal operational. Underpinning these stages is a series of mental constructs that a child must build to aid their understanding of the world. First, the child builds schemata, mental patterns which enable the individual to understand and interact with the world. Schemas continue to be built upon and develop as an individual encounters new experiences and their learning increases. For schemas to develop, a process of assimilation needs to occur; this involves understanding new objects, ideas or situations fitting in with existing knowledge. Accommodation occurs when new information is taken in, and an existing schema is modified to absorb this knowledge.

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Piaget believed that equilibrium occurs when a child achieves a balance between assimilation and accommodation. As a child moves through developmental stages, it is important to balance applying previous knowledge and modifying behaviour to account for new knowledge. This helps to explain how a child progresses through the stages (Hill, 2001, pp35). The first stage, the sensorimotor stage, takes place between birth and the age of two. This stage is characterized by the infant developing their thoughts through sensory information and actions. During this stage, the infant is deeply egocentric and cannot differentiate between itself and its environment. During this stage, Piaget describes schemas as reflex actions that gradually become more intentional. One of the major defining factors of this stage is the development of “object permanence”.

This is the understanding that objects can still exist even when they are hidden. Piaget investigated this theory by observing his own children when he hid an object from them. He found that a child will not search for an object hidden from view between the ages of 0-5 months, but by the age of 8 months, the child will actively look for it (ibid, pp36). According to Piaget, around the age of 2-7 years, a child will become pre-operational. Schemas are now largely symbolic, represented internally by words. The child is not mentally developed enough to carry out logical operations and still has difficulty understanding that others do not see, think and feel things as they themselves do (ibid). To demonstrate this, Piaget and Inhelder (1956) carried out their Three Mountain Experiment. Children were shown a series of photos of the mountains from different viewpoints and were asked to pick the one which best fitted the view the doll had.

Four-year-olds failed to pick the correct view, and six-year-olds, although more aware of other viewpoints, tended to be incorrect. On the other hand, seven and eight-year-olds consistently got the answer right (Gross et al., 2006). There is, however, some evidence to suggest that Piaget’s mountain experiment may have been too difficult for children to demonstrate their abilities as the task had little human meaning to them. Hughes (1975) repeated the mountain experiment by hiding a doll from two police officers. This made more “human sense” to the children by requiring them to see things from another person’s perspective with an understandable reason for doing so (Hill, 2001, pp 36). By doing this, Hughes found that 90% of 3 – 5-year-olds were successful in the task, from which he concluded that it was a lack of understanding rather than egocentrism that prevented them from doing the task correctly (

Pre-operational children also lack the ability to understand that some things remain unchanged despite them looking visibly different. Piaget thought that this was because children of this age are unable to pay attention to more than one character in a situation and can reverse the operations in their heads (ibid). Piaget conducted a liquid conservation experiment to show this (see picture 2 below). Even though the children saw the same amounts of liquid in the original beakers, when the liquid was poured into the tall, thin beaker, pre-operational children said that this one contained more liquid despite agreeing that none had been taken out or spilt. More recent research has questioned Piaget’s view of the conservation abilities of pre-operational children.

McGarrigle et al. (1974) repeated Piaget’s conservation task with 6-year-old children, using counters arranged in rows of equal numbers. When the researchers muddled up the counters, only 16% of the children thought that the counters were the same. However, when a “naughty teddy” muddled them up, 62% of children could give the correct answer (Hill, 2001, pp37). This seems to contradict Piaget by suggesting that children are better able to conserve than he thought if the situation is given a meaning that children understand. The Concrete Operational Stage occurs from 7 – 11 years old and is the third stage of Piaget’s theory. This stage is characterized by the child’s ability to perform several more complex cognitive tasks, including classification, seriation, reversibility, decentration and conservation.

Schemas during this stage now become logical and mathematical. By now, children are less self-centred and have the ability to think logically but only about objects that exist in reality. By mastering conservation, a child can now accurately judge this type of task but still needs to be able to see the transformation taking place as they are still unable to process this information purely in their head (Cullis et al., 1999). This stage also sees a child becoming decentralized. About the liquid conservation task, they can see how changes in one area can be compensated in another area; the thinner width of the second beaker compensates for the increased height (Cullis et al., 1999).

Moving on from the concrete operational stage, around the age of 11 onwards, a child will enter Piaget’s formal operational stage. From this age, a child’s mental structures are developed enough to think and apply reasoning in abstract terms. They no longer need to see an example of action or problem physically; instead, they can manipulate the ideas in their heads to reach the correct conclusion. They can also grasp hypothetical situations and problems that they may never have encountered before and will tackle problems systematically (Hill, 2001, pp 37). There is evidence to suggest, however, that formal operational cognition is culturally specific. For example, Gladwin (1970) found that the Pulawat navigators of Polynesia showed complex cognitive abilities when guiding their canoes at sea but were likely to fail standard western tests for cognitive development (ibid).

Many psychologists have countered Piaget’s theory over the years. However, its main strength still lies in the fact that the theory accounts for biological and environmental factors in the development of cognitive intelligence. His studies have also meant that much more research has been carried out into cognitive development, which has increased the overall understanding of the subject. Linking into this idea, other psychologists have used Piaget’s theories to base their own research, enabling questions raised by Piaget’s views to be answered. However, Piaget has been criticized on several levels. His scientific methods have been disparaged for being too informal with small sample sizes, and his interview methods being too child-centred and not easily comparable with other results.

As a result, Piaget made generalized conclusions that may not apply to all children. Psychologists such as Vygotsky and Bruner have noted that Piaget’s theory fails to consider how social interaction with the world and language can impact cognitive development. By only seeing a child as an individual, Piaget does not consider the contribution parents and others may have on cognitive development. Bruner’s (1971) model of cognitive development consists of three modes of representation, which, whilst they are sequential, are not hierarchical and remain with an individual throughout their life. These are the enactive mode, similar to Piaget’s sensorimotor stage, where knowledge is acquired through actions; the iconic model, where knowledge is acquired from likenesses and images; and the symbolic mode, which allows children to store information by way of symbols and language.

Bruner places much emphasis on the importance of social factors, including language, social interaction and experience. Piaget considered language relatively unimportant, viewing it only as an expression of thought instead of Bruner, who saw language as symbolic, logical and operational thought (Hill, 2001 pp 40). To illustrate this, Francoise Frank, reported by Bruner (1964), showed that pre-operational children were much better at liquid conservation tasks if they were encouraged to use their verbal skills. Frank screened much of the beakers used so the children would not rely so much on visual skills, instead of relying on verbal descriptions and subsequently being better able to conserve.

As a result, the number of children able to successfully pass the conservation task vastly increased from 20% in Piaget’s tests to 70% for 5-year-olds and 50% to 90% for 6-7-year-olds (Hill, 2001, pp40). Bruner also stressed the importance of cultural background as he maintained that culture determines the kind of person an individual will become. His view was that culture provides the directions to how a human should develop, clearly disagreeing with Piaget’s view that a child learns independently ( Vygotsky was also a proponent of the importance of social interaction and language in cognitive development.

In contrast to Piaget, who thought learning occurred individually, Vygotsky maintained that cognitive development happened because of the social input that children receive from others (ibid). Therefore, Vygotsky formulated the idea of “scaffolding,” whereby adults provide a support system to help children understand and achieve higher levels of development. According to Vygotsky, because cognitive development is a combination of knowledge achieved between the child and society, it is true to say that a child’s intellectual potential is greater if they are working with support and input from adults than if they were working alone. This is called the “zone of proximal development” (Hill, 2001, pp 41).

In conclusion, despite Piaget’s theory receiving criticism for its apparent lack of emphasis on the social environment, the input of others and the role of language, it still is an important model of cognitive development which has widely influenced teaching practices and has been a starting point for other psychologists to develop their own ideas. Piaget saw children being central to their own learning and proposed that they discover things for themselves, which has been core to many student-centred learning strategies still used in the modern classroom.


  • Cullis, T., Dolan, L., Groves, D., Psychology for You, (1999), Nelson Thornes, Cheltenham.
  • Gross, R., Rolls, G., Essential Psychology, (2006), Hodder Arnold, United Kingdom.
  • Hill, G., AS Level Psychology Through Diagrams (2001), Oxford University Press, United Kingdom.
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