Jean Piaget is widely recognised as the most influential developmental psychologist of the twentieth century. His central thesis is that human development occurs through the interaction between maturational processes and the environment. In line with Piagetâs initial training as a biologist, maturation in turn depends upon the development of a personâs nervous system: biological structure dictates the parameters of a personâs functioning and the sequence of stages through which she passes.
Similar to Kelly, however, Piaget espouses a constructivist position. The development of human knowledge is also an active process, transforming sensory information from the external environment.
I find myself opposed to the view of knowledge as a passive copy of reality. . . . I believe that knowing an object means acting upon it, constructing systems of transformations that can be carried out on or with this object. Knowing reality means constructing systems of transformations that correspond, more or less adequately, to reality. The transformational structures of which knowledge consists are not copies of the transformations in reality; they are simply possible isomorphic models among which experience can enable us to choose. Knowledge, then, is a system of transformations that become progressively adequate. (Piaget, in Evans, 1973: 53)
Piaget proposes that a newborn baby already possesses a set of skills – such as the ability to grasp objects or to suck a nipple – to enable her to act, mentally and physically, in the world. The mere existence of such skills presupposes an underlying mental structure or internal representation of the related sequence of actions, which initially in a personâs life will comprise inherited reflexes. Piaget adopts the term schema (schemata in the plural) to refer to such internal structures. Through the innate tendency Piaget labels organisation, furthermore, existing schemata are co-ordinated and combined into more complex systems. This can occur early in an infantâs development when the act of feeding from a nipple or bottle comes to represent an integration of the looking, grasping and sucking schemata.
A childâs knowledge develops, Piaget continues, through an interaction of such schemata with the external environment. Two outcomes can occur. Firstly, the information from the environment may fit into the schema, a process Piaget calls assimilation. The grasping schema, for instance, enables the infant to grip a small range of convenient objects. Piaget also considers play to illustrate assimilation, the child striving to fit outside reality into her own needs and views. Since any schema can only represent a portion of reality, however, assimilation is not always possible. Accommodation must take place. The child restructures her schemata in line with the demands of the environment. Hence, the grasping schema becomes modified to cater for larger and heavier objects and those of a different shape. Imitation is another example of accommodation, the child changing some of her own schemata by copying another personâs behaviour. More generally, whereas recognition is principally assimilation, learning (adding new information) is principally accommodation. Piaget argues that a fundamental equilibrium or adaptation is achieved through the complementary processes of assimilation and accommodation. The success or failure of this innately programmed, though manifestly idiosyncratic, venture also determines cognitive ability.
Concerning specific, biologically based, stages of human cognitive development, Piaget cites four in invariant sequence, all representing distinctly different ways of viewing the world:
- the sensorimotor stage
- the preoperational stage
- the concrete operational stage
- the formal operational stage.
The child progresses from being incapable of independent thought to being conversant with abstract logical thought.
The sensorimotor stage occurs between birth and approximately the age of two. Gradually, the infant becomes able to distinguish himself from his surroundings. Not only does he not think in the commonly understood meaning of the word, but he is still grappling with basic concepts which ordinary thinking takes for granted: for example, that grasped objects drop when released or that fulfilling needs requires more than random activity. The infant concentrates mainly upon seeking and repeating satisfying events, initially concerning his own body (primary circular reactions), and later concerning objects, such as rattles (secondary circular reactions). He is becoming more acquainted, moreover, with the notion of causality. Pulling a tablecloth, for instance, is linked to bringing objects closer. Between eight months and a year old, awareness of object permanence (or object constancy) develops. For the growing infant, an object being out of immediate sensory experience no longer so definitely means its being out of existence. Similarly, there is a shift from dependence upon physical action to being able to represent mentally events not currently present in the childâs perceptual field. In short, the child begins to symbolise and to be freed from the present moment.
The preoperational stage, between the ages of approximately two and seven, extends basic symbolisation towards the use of language and the development of imaginative play. During the preconceptual sub-stage, between the ages of approximately two and four, the child learns to use words as labels. Words effectively become mental objects endowed with the meaning of the objects they represent in the real world. (The capacity for such symbolisation may distinguish humankind from most other species, who are consigned to a far greater degree to learn behavioural lessons anew.) During the intuitive sub-stage, between the ages of approximately four and seven, the child begins to use concepts, enabling her to sort objects by colour, size and shape. She remains, however, egocentric: able to construe the world only from her own perspective and unable to decentre herself from the focus of her ownÂ perceptual world. This is illustrated by various limitations in her thinking. She displays irreversibility, for example: able to answer correctly and affirmatively when asked if she has a sister, but not being able to comprehend that her sister also has a sister.Â The overriding constraints of centration may be highlighted through the childâs lack of mastery over the principles of conservation (understanding that number, volume and mass stay constant despite perceptual changes in their grouping or form).
The concrete operational stage, between the ages of approximately seven and 11, signals a decrease in the childâs egocentricity. He becomes better able to empathise and, hence, take on the role of another person. Experiments have also shown that the conservation difficulty, characteristic of the preoperational stage, is overcome. It becomes increasingly possible for the child to use logical thought, through reversibility, classification (using categories and hierarchies) and seriation (placing objects in order of measurement). Such problem-solving ventures are only feasible, however, with live tangible objects rather than linguistically in the absence of such objects.