1. Piaget's Theory of Cognitive Development

Jean Piaget's theory^[1] consists of four stages: Sensorimotor: (birth to 2 years), Preoperations: (2 to 7 years), Concrete operations: (7 to 11 years), and Formal Operations: (11 to 16 years). Each stage has at least two substages, usually called early and fully.

1.1. Underlying Assumptions

• Each stage lays the foundation for the next.
• Everyone goes through the stages in the same order.
• Each stage is qualitatively different. Meaning it is a change in nature, not just quantity
• The child is an active learner. Basically they have to do it on their own, they cannot be told.

1.2. Sensorimotor Stage (Birth to 2 Years)

This stage is represented when infants obtain some control over their surroundings by sensory and motor schemes. ^[2] Infants start to identify their actions and the consequences of their actions. ^[3]

A child comes into the world knowing almost nothing, but they have the potential that comes in the form of:

• Brain makeup
• Reflexes e.g. sucking and visual orienting
• Innate tendencies to adapt to environment

Infants use these potentials to explore and gain an understanding about themselves and the environment. They have a lack of object permanence, which means they have little or no ability to conceive things as existing outside their immediate vicinity. For example: when you place a barrier, such as a piece of wood, in front of an object an infant will believe that the object is nonexistent.

1.3. Object Permanence

Study

• Infants do not grasp the concept of object permanence when they do not realize that an object exists even when it is not visible at the moment.
• When an object or toy is hidden from an infant they almost immediately lose interest and fail to search for the toy. This is common in infants that are eight months or younger. ^[4]
• Children who are around eight months can form a mental representation of an object in their head proving that they obtain object permanence (sensory motor stage)

1.4. Sensorimotor Play

This play does not provide a purpose other than sensation:

• Swinging on a swing; enjoys the movement
• Singing songs and simply playing with sounds such as 'Tra-la-la."^[5] the sound's purpose is only for the satisfaction they bring
• Some play includes listening, tasting and smelling

Substages of Piaget's sensorimotor stage

1.5. Preoperational Stage (2 to 7 Years)

Preoperational intelligence means the young child is capable of mental representations, but does not have a system for organizing this thinking (intuitive rather than logical thought). The child is egocentric – which is they have problems distinguishing from their own perceptions and perceptions of others. A classic example is, a preoperational child will cover their eyes so they can not see someone and think that that person can not see them either.

The child also has rigid thinking, which involves the following:

• Centration – a child will become completely fixed on one point, not allowing them to see the wider picture. For example, focusing only on the height of the container rather than both the height and width when determining what has the biggest volume.
• State – can only concentrate on what something looks like at that time.
• Appearance – focuses on how something appears rather than reality.
• Lack of Reversibility – can not reverse the steps they have taken. Does not realize that one set of steps can be cancelled by another set of steps.
• Lack of Conservation – realizing that something can have the same properties even if it appears differently.

1.6. Concrete Operations (7 to 11 Years)

• Intelligence is now both symbolic and logical.
• Acquires ‘operations’ = a set of general rules and strategies.
• The most critical part of operations is realizing ‘reversibility’ = both physical and mental processes can be reversed and cancelled out by others.

The concrete operational child will overcome the aspects of rigidity apparent in a preoperational child. These are:

• lack of reversibility
• states
• appearance
• conservation

The tasks of concrete operations are:

• Seriation – putting items (such as toys) in height order.
• Classification – the difference between two similar items such as daisies and roses.
• Conservation – realising something can have same properties, even if it appears differently.

It is important to realise that operations and conservations do not develop at the same time. They develop gradually and are not an ‘all or nothing’ phenomenon. For example, the first to develop is number conservation followed by mass conservation, area conservation, liquid conservation and finally solid volume conservation. Thinking is not abstract. It is limited to concrete phenomena and the child’s own past experiences.

1.7. Formal Operations (11 to 16 Years)

• Child is capable of formulating hypotheses and then testing them against reality.
• Thinking is abstract, that is a child/adolescent can formulate all the possible outcomes before beginning the problem. They are also capable of deductive reasoning.

2. Limitations of Piaget's Theory

A popular criticism is that Piaget underestimated the abilities of an infant. Studies have shown that they have more of a capacity in memory and understanding of objects than he believed. ^[6]

3. Neo-Piagetian and Post-Piagetian Stage Theories

Juan Pascaual-Leone was the first to propose a neo-Piagetian stage theory. Since that time there have been several neo-Piagetian theories of cognitive development.^[7] Only the ones that cover at least infancy through adulthood are mentioned here. These include the theories of Robbie Case, Grame Halford, Andreas Demetriou and Kurt W. Fischer. The theory of Michael Commons' model of hierarchical complexity is also relevant. The description of stages in these theories is more elaborate and focuses on underlying mechanisms of information processing rather than on reasoning as such. In fact, development in information processing capacity is invoked to explain the development of reasoning. More stages are described (as many as 15 stages), with 4 being added beyond the stage of Formal operations. Most stage sequences map onto one another. PostPiagetian stages are free of content and context and are therefore very powerful and general.

4. List of Books Formulating Stage Theories

• Giambattista Vico (1725) The New Science
• G.W.F. Hegel (1807) The Phenomenology of Spirit
• Auguste Comte's Law of three stages in 'Plan de travaux scientifiques nécessaires pour réorganiser la société (Plan of scientific studies necessary for the reorganization of society, 1822).
• Søren Kierkegaard (1843) Either/Or, Stages on Life's Way (1845)
• Karl Marx (1867) Das Kapital
• James George Frazer (1890) The Golden Bough
• Sigmund Freud (1900) The Interpretation of Dreams
• Wilhelm Wundt (1912) Elemente der Völkerpsychologie (The Elements of Social Psychology)
• Oswald Spengler (1918) The Decline of the West
• Lewis Mumford (1934) Technics and Civilization
• Stephen Pepper (1942) World Hypotheses
• Jean Gebser (1949) The Ever-Present Origin
• Jean Piaget (1950) The psychology of intelligence
• Northrop Frye (1957) Anatomy of Criticism
• Hayden White (1973) Metahistory
• Jane Loevinger (1976) Loevinger's stages of ego development
• Clare W. Graves (1978/2005)† The Never Ending Quest
• Kieran Egan (1979) Educational Development^[8]
• Ken Wilber (1995) Sex, Ecology, Spirituality

†Posthumously published in the later year listed, primarily written by the earlier year.