By the time you reach adulthood you have learned a few things about how the world works. You know, for instance, that you can’t walk through walls or leap into the tops of trees. You know that although you cannot see your car keys they’ve got to be around here someplace. What’s more, you know that if you want to communicate complex ideas like ordering a triple-shot soy vanilla latte with chocolate sprinkles it’s better to use words with meanings attached to them rather than simply gesturing and grunting. People accumulate all this useful knowledge through the process of cognitive development, which involves a multitude of factors, both inherent and learned.
Stage theories of development, such as Piaget’s stage theory, focus on whether children progress through qualitatively different stages of development. Sociocultural theories, such as that of Lev Vygotsky, emphasize how other people and the attitudes, values, and beliefs of the surrounding culture, influence children’s development.
Swiss psychologist Jean Piaget proposed that children’s thinking progresses through a series of four discrete stages. By stages he meant periods during which children reasoned in the same way about many superficially different problems, with the stages occurring in a fixed order and the thinking within different stages differing in fundamental ways. The four stages that Piaget hypothesized were the sensorimotor stage (birth to 2 years), the preoperational reasoning stage (2 to 6 or 7 years), the concrete operational reasoning stage (6 or 7 to 11 or 12 years), and the formal operational reasoning stage (11 or 12 years and throughout the rest of life).
During the sensorimotor stage, children’s thinking is largely realized through their perceptions of the world and their physical interactions with it. Their mental representations are very limited. Consider Piaget’s object permanence task, which is one of his most famous problems. If an infant younger than 9 months of age is playing with a favorite toy, and another person removes the toy from view, for example by putting it under an opaque cover and not letting the infant immediately reach for it, the infant is very likely to make no effort to retrieve it and to show no emotional distress (Piaget, 1954). This is not due to their being uninterested in the toy or unable to reach for it; if the same toy is put under a clear cover, infants below 9 months readily retrieve it (Munakata, McClelland, Johnson, & Siegler, 1997). Instead, Piaget claimed that infants less than 9 months do not understand that objects continue to exist. This is called object permanence.
During the preoperational stage, according to Piaget, children can solve not only this simple problem (which they actually can solve after 9 months) but show a wide variety of other symbolic-representation capabilities, such as those involved in drawing and using language. However, such 2- to 7-year-olds tend to focus on a single dimension, even when solving problems would require them to consider multiple dimensions. This is evident in Piaget’s (1952) conservation problems. For example, if a glass of water is poured into a taller, thinner glass, children below age 7 generally say that there now is more water than before. Similarly, if a clay ball is reshaped into a long, thin sausage, they claim that there is now more clay, and if a row of coins is spread out, they claim that there are now more coins. In all cases, the children are focusing on one dimension, while ignoring the changes in other dimensions (for example, the greater width of the glass and the clay ball).
Children overcome this tendency to focus on a single dimension during the concrete operations stage, and think logically in most situations. However, according to Piaget, they still cannot think in systematic scientific ways, even when such thinking would be useful. Thus, if asked to find out which variables influence the period that a pendulum takes to complete its arc, and given weights that they can attach to strings in order to do experiments with the pendulum to find out, most children younger than age 12, perform biased experiments from which no conclusion can be drawn, and then conclude that whatever they originally believed is correct. For example, if a boy believed that weight was the only variable that mattered, he might put the heaviest weight on the shortest string and push it the hardest, and then conclude that just as he thought, weight is the only variable that matters (Inhelder & Piaget, 1958).
Finally, in the formal operations period, children attain the reasoning power of mature adults, which allows them to solve the pendulum problem and a wide range of other problems. The formal operations stage tends not to occur without exposure to formal education in scientific reasoning, and appears to be largely or completely absent from some societies that do not provide this type of education.
Cognitive Development and Culture
Although Piaget’s theory has been very influential, it has not gone unchallenged. Recent research indicates that cognitive development is considerably more continuous than Piaget claimed. For example, Diamond (1985) found that on the object permanence task described above, infants show earlier knowledge if the waiting period is shorter. At age 6 months, they retrieve the hidden object if the wait is no longer than 2 seconds; at 7 months, they retrieve it if the wait is no longer than 4 seconds; and so on. Even earlier, at 3 or 4 months, infants show surprise in the form of longer looking times if objects suddenly appear to vanish with no obvious cause (Baillargeon, 1987).
Similarly, children’s specific experiences can greatly influence when developmental changes occur. Children of pottery makers in Mexican villages, for example, know that reshaping clay does not change the amount of clay at much younger ages than children who do not have similar experiences (Price-Williams, Gordon, & Ramirez, 1969). In a study of tribal children (Inuit of Canada, Baoul of Africa and Aranda of Australia) researchers found differences in the ages at which children reached certain stages and acquired certain skills (Dasen, 1975). About 50% of the Inuit children solved a visual spatial test by the age of 7, 50% of the Aranda children solved the same task by the age of 9; however the Baoul children did not solve the task until the age of 12. On a conservation task the ages of skill acquisition reversed. The differences seem related to the living environment of the children – the Baoul children lived in permanent settlements while the Inuit and Aranda tribes are nomadic. Demands of daily life shape the cognitive development and different societies’ value and reward different skills and behaviors.
A main figure whose ideas contradicted Piaget’s ideas was the Russian psychologist Lev Vygotsky. Vygotsky stressed the importance of a child’s cultural background as an effect to the stages of development. Because different cultures stress different social interactions, this challenged Piaget’s theory that the hierarchy of learning development had to develop in succession. Vygotsky introduced the term Zone of Proximal Development as an overall task a child would have to develop that would be too difficult to develop alone.
Overall, Piaget’s theories are widely recognized as making key contributions to the field of child development and helped pave the way for further empirical study. Cross-cultural testing has challenged many of his ideas, but the overall hierarchy of stages and sub-stages in cognitive development appears to be universal. Timing, ages, and capabilities during each stage appear to vary according to cultural context and enculturation patterns.