Briefly describe Piaget's theory of child development.

In essence, there are two main theorists behind the stages of child development: Piaget and Vygotsky. Piaget's theory is based on the assumption of the existence of schemas. Schemas are defined by Piaget as "A cohesive, repeatable action sequence possessing component actions that are tightly interconnected and governed by a core meaning" which is formed in the mind as a mental representation. These schemas provide the building blocks of cognitive models. Piaget argues that a number of these schemata are innate, such as the grasping reflex or a sucking reflex. As the child gets older and increases in experience with the surrounding environment, these schemata develop and new ones form, such as crawling which is then followed by walking. Part of Piaget's theory is based around assimilation and accommodation, when existing schemata are either used to deal with a new object or situation (assimilation) or the existing schemata need to be altered to deal with a new situation (accommodation). Equilibrium drives development according to Piaget, and occurs when the schemata can deal with the majority of novel information via assimilation. When this is not the case (disequilibrium), accommodation takes over to acquire new schemata, which will then in turn follow a similar process of assimilation in the future when new challenges are faced.

Due to this model, Piaget asserts that development is not a steady, slow process but occurs in big leaps, when the child is typically of a certain age when new challenges are faced. This gives birth to Piaget's four stages of cognitive development: The sensorimotor stage ( 0 > 2 years), the pre-operational stage (2 years > 7 years), the concrete operational stage (7 years > 11 years) and the formal operational stage (11 years +). Every child passes through every stage in the same order, albeit at differing rates, depending on individual differences in biological maturation and environmental interaction. The sensorimotor stage is all about the development and assertion of object permanence - the knowledge that an object exists even when it is out of view as it requires the ability to form a mental representation (i.e a schema) of the object. The pre-operational stage is best defined as the point when children can think symbolically, but thinking is very much stilol rooted in egocentrism. The concrete operational stage is the point Piaget describes the child able to conserve information (i.e. understand that quantity can change, even if appearance remains the same, e.g. showing in front of the child, moving 100ml  eachof water in a bowl, a tall glass and a small glass will make the amounts of water look different, but the child will be able to recognise that it is the same amount of water). The final stage of development, which lasts into adulthood is the formal operational stage, when people can develop the ability to think abstractly and to test hypotheses etc.