Infant exhibiting undeveloped object permanence
Infant exhibiting undeveloped object permanence


‍Stage Theory

Piaget's stages each identified a normative age range for normal cognitive development. However, numerous studies have found that Piaget's stages may have underestimated child developmental capacities. Baillargeon et al. found that infants at 3.5-4.5 months displayed an understanding of object permanence; this is far before Piaget stated they should be able to understand this.

Lourenco et al. found that 5-6 year old children are capable of concrete operational thought; according to Piaget, children should not be capable of concrete operation thought until 7-11 years.

Additionally, child development is not as consistent as the stages suggest. Piaget would claim that a child has an understanding of certain concepts and is able to apply this concept to every area of the child's life or does not understand it; there is no transitional period. However, some children learn to apply the concepts more quickly in terms of quantities, space, social behavior, narrative, music, or motor behavior than other domains.

Methodological Flaws

When Piaget developed his theory, he used a combination of observation and interviews to test his hypotheses. He used observation with infants and conducted interviews with children old enough to communicate verbally. Piaget began also using observation with older children towards the end of his career. While observation and conducting interviews can be empirically sound forms of research, Piaget's studies had many methodological flaws.

Piaget based his theory of infants on his own three children. It could be argued that he never really had a concerted interest in figuring out child cognitive development but that he was intrigued by his kids' discovering of the world. ‍This presents several issues and seriously inhibits generalizability. First, this is a very small sample size, so any findings may only be unique to Piaget's three children. There also might have been bias in the interpretation; Piaget also could have reinforced his children to behave in certain way over time. Since Piaget was the only observer, there was no measure of reliability from two independent observers.

Piaget used the clinical method to derive his findings and the issues were spontaneous fantasy, suggestion, and chance. Experimentalists working within an empirical framework argued that the method was more a logic of discovery rather than logic of justification or truth testing.
He was much better at describing processes rather than explaining how they operate. In his use of the method, he could describe early egocentric thought and language. Both the reality and the explanation given by the child were pertinent. The question of how we get from strict egocentrism (everything only affects me) to social consideration (viewpoints of others) is not addressed by Piaget. He merely saw social interaction as a function of cognitive development, not the other way around. In his observations, he noticed that responses would become more socially acceptable and less spontaneous as the children advanced through stages.

Piaget did not report any demographic information or specific information concerning methodology. Also, as Piaget was the only researcher, there were no other independent observers to confirm or disagree with his conclusions.

Piaget's interviews may have tested verbal ability, rather than the concepts he was testing. Multiple studies have been conducted and have shown that Piaget's interviewing techniques underestimated the abilities of children. Furthermore, Chapman (1988) illuminates
"epistemological realism" in that Piaget never truly distinguishes between the child's reality and the scientist's reality. Epistemologically, this is an affront on the integrity of knowledge production.


In Piaget's methodology, his sample was not only very small but also lacking in diversity variables. Piaget believed his stages of development are universal so studying diverse populations would not influence his data. However, he did not test the universality of his theory by controlling for variables like race, ethnicity, SES, disability, etc. Also, Piaget was concerned with "normal" development but never operationally defined what he thought normal was‍. He had no way of explaining individual differences. Clearly a diversity issue but Piaget could also not explain differences of individuals at the very basic level of his own theory, as to say one child should not be able to develop the tasks of a given stage of development before another.