In the first stage of cognitive development, the sensori-motor stage, sensory input is co-ordinated with motor actions through circular reactions, where children repeat the same action over and over to test sensori-motor relationships. One development of this stage is object permanence, the recognition that objects continue to exist even when out of sight. In stage 2, the pre-operational stage, which develops between 2 and 7 years, thought, becomes increasingly symbolic as they begin to represent their world in words and images. The child is not yet capable of reversibility of thought, which results in the child’s tendency towards egocentrism, a failure to understand that what the child sees is relative to his or her own perspective. The child is also guilty of centration, a tendency to focus attention on one aspect of a situation and not take other details into account. In stage 3, the concrete operational stage, the child develops the basics of logical operations such as conservation (e.g. several different sizes of juice on a table, children choose the glass that is the tallest because they perceive the taller glass as having more juice inside of it) and seriation (which refers to the ability to sort objects or situations according to any characteristic, such as size, color, shape, or type) although he or she cannot solve such problems when in abstract form. In the final stage, the formal operational stage, from age 11 onwards, the child has a better understanding of cause and effect of relationships, and is now able to develop their own theories about the world, which they can test in an organised way. They can also understand and apply abstract concepts.
Piaget’s theory is based on studies of intelligent European children. However, research carried out in other cultures has shown that concrete reasoning may be more highly regarded, which may explain why children in those cultures often do not display formal operational reasoning. A problem with some of the earlier research on this theory is that it often failed to consider other explanations for the findings. For example, the lack of object permanence in infants may be due to the lack of an ability to uncover the object. Research that has used surprise to test object permanence has found that infants aged 4 months showed this ability (Bower et al 1971). In many of the studies, the tasks used were confusing, e.g. conservation failures may have been due to the use of two questions, as when one question was asked younger children did better (Samuel and Bryant, 1984). Many of the tasks were unrealistic, e.g. the three mountains used to test for egocentricity. This problem was easier when children were given a more realistic test (i.e. the policeman and the naughty boy, Hughes 1975). Children may also have displayed demand characteristics. Mc Garrigle and Donaldson (1974) found that when transformation in conservation tasks was accidental (using naughty teddy) children were more successful than when the transformation was deliberate.
Limitations of theory include the fact that Piaget may have overestimated the ability to use abstract logic in the formal operational stage. Dasen (1994) found that only one third of adults reach this stage. There is little empirical support for the concept of equilibration; in fact some research has shown that children may learn better in situations of mild conflict (Inhelder et al 1974). Many psychologists see stage theories such as Piaget’s as being too rigid. Piaget introduced the idea of horizontal delagage, the fact that certain cognitive abilities are shown in some circumstances but not others, to deal with this criticism. Despite this, strength of Piaget’s theory is that it has been highly influential and has had major effect on education in the UK.