4.4 Structure and stages
Piaget's developmental processes can be described in the context of infant behaviour to show how they explain behaviour becoming more adapted, in a step-by-step way. First, the infant develops the ability to combine different schemas in order to achieve new ends. Then, the child represents schemas ‘internally’; they become representations of actions (‘operations’). Finally, by the age of 2 years, the child becomes capable of combining representations into sets of actions. He saw one of the goals of the first 2 years of life as being the achievement of a set of operations that are represented as a structure; not just a random collection of unconnected actions, but a co-ordinated set of possibilities for manipulating the world.
Piaget's theory described four stages of intellectual development: these are outlined in Box 4.
Box 4 Piaget's stage theory of development
Stage 1: Sensori-motor stage (from birth to about 2 years)
Children are born with innate behavioural patterns (reflexes), which are their first means of making sense of their world. Children can take in new knowledge and experiences as far as they are consistent with their existing behaviours. Eventually they begin to generate new behaviours in response to their environment (schemas). As contact with the environment increases, they develop more elaborate patterns of behaviour. This stage ends when children are able to represent their behaviours internally.
Stage 2: Pre-operational stage (from about 2 to 6 years)
Children begin to use combinations or sequences of actions that can be carried out symbolically. For example, putting two objects together can be represented symbolically as an abstract mathematical principle (addition). However, at this stage children are only able to perform them as actions in the real world rather than to represent them symbolically.
Stage 3: Concrete operations stage (from about 6 to 12 years)
During this stage children are mastering the ability to act appropriately on their environment by using the sequences of actions they acquired in the pre-operational stage. They develop the ability to generate ‘rules’ based on their own experiences (e.g. noticing that adding something to a group of objects always ‘makes more’). Children can now manipulate their environment symbolically too, so they can imagine adding ‘more’ to a group of objects. They are still only able to understand the rules that they have had concrete experience of, but can now begin some mental manipulation of these concepts. What they are unable to do at this stage is use rules to anticipate something that could happen, but that they have not yet experienced.
Stage 4: Formal operations stage (from about 12 years onwards)
By this stage children can reason in a purely abstract way, without reference to concrete experience. They can tackle problems in a systematic and scientific manner and are able to generate hypotheses about the world based on their accumulated representations of it.
Each stage is, according to Piaget, marked by characteristic modes of thought. The general progression through the stages is such that thought, and consequent action, become progressively less ‘centred’. Through increasing abstraction of representation, ‘mental operations’ become less tied to concrete realities and egocentric perceptions.
Using the word ‘stage’ to describe a period of development suggests that children do different things at each of these stages. This idea of stage makes it possible to describe these changes in terms of particular behaviours and ways of solving problems that appear to dominate in particular age ranges. However, it should be noted that Piaget's theory recognises that some children develop more slowly or faster than others, and the development of an individual child may not be maintained at a constant rate. For example, illness can slow development down and, when they have recovered, children often show a spurt of ‘catch-up’ growth, both mentally and physically.
An implication of Piaget's theory is that there is some sort of abrupt change or discontinuity in development that establishes a boundary between one stage and the next. Indeed, if there is no such boundary implied, then it is rather dubious whether we would be justified in calling a particular period a ‘stage’ at all. But using the word ‘stage’ also often carries with it a notion of sequence, that one stage must follow another stage in a set order, or even that there is a causal relationship in which the completion of one stage is deemed a necessary condition for the transition to the next one. Piaget's stages form a necessary sequence, with no child missing out any of the stages, nor passing through them out of sequence.
So, how did Piaget determine when a child passed from one stage to the next? This was achieved by administering sets of experimental tasks, each task being linked to a core concept associated with a given stage of development. For example, pre-operational children, in Piaget's theory, are basically egocentric, centred on their own perceptions because they are still very tied to the concrete world and their actions on it. Also, because this group of children lack the ability to reflect on operations, their understanding of the world tends to focus on states, rather than on transformations. Similarly, such children are unable to comprehend points of view different from their own.
One of the concepts that Piaget suggested was absent from pre-operational children's representation of the world was conservation – the understanding that a quantity will be the same, even if its manner of presentation changes. For example, a quantity of water remains the same whether it is presented in a tall, thin glass or a short, wide glass. His conservation of liquid task involves three basic steps:
The child is shown two identical transparent beakers, each about two-thirds full of water. They are placed side-by-side in front of the child. The experimenter seeks the child's agreement that the quantities of water in each are the same, if necessary adding or taking away small amounts until the child is satisfied.
The water from one beaker is all poured into another beaker, which is either taller and narrower than the first one, or shorter and wider.
Typically, up to the age of about 6 or 7 years, children will assert, when asked, that the amount of liquid has changed. If the children are then asked why this is so, they will tend to say something like ‘because it's taller’. The children's answers seem to indicate that their judgement of quantity is centred on the visual change brought about by the transformation (see Figure 6).
Piaget considered conservation (the understanding that a quantity remains the same, in spite of any transformation of the way in which it is presented) not just in relation to amounts of liquid, but also in relation to mass, volume, weight, area, length and number. For example, to assess conservation of mass, a child is shown two balls of clay and asked whether each ball has the same amount in it. When the child is satisfied that both are equal, one of the balls is rolled out into a sausage shape and placed alongside the other, untransformed, ball. Then, just as in the conservation of liquid task, the child is asked whether there is more material in the sausage shape, or less, or the same amount. A ‘non-conserver’ will now say that the amounts are no longer the same, as the sausage shape now has more in it.
Piaget's theory involves the child progressively becoming freed from the constraints of their own perspective and the concrete objects around them, as mental operations become more abstract. This process reaches its end-point in Piaget's final stage, when operations become wholly abstract and the child becomes able to reason purely hypothetically and systematically.