The 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 similarly about many superficially different problems, with the stages occurring in a fixed order and the thinking within different stages differing in fundamental ways. Piaget believed that the timing of his stages was biologically defined - no amount of coaching could lead a child to progress more rapidly from one stage to the next.
The four stages that Piaget hypothesized were as follows:
Sensorimotor (birth to 2 years) - knowing in this first stage is limited to sensing and doing
Preoperational (2 to 6 or 7 years) - while no longer limited to the here and now, in this 2nd stage children do not understand that we all experience the world differently and exhibit various limits in their ability to reason
Concrete Operational (6 or 7 to 11 or 12 years) - during Piaget's 3rd stage, the hallmarks of the preoperational stage are gone, but marked limits to problem-solving are evidence
Formal Operational (11 or 12 years and throughout the rest of life) - Piaget believed his final stage was universal, a conclusion that we now know to be incorrect - as well as his belief that it was commonly achieved so early
During the sensorimotor stage, children’s thinking is largely realized through their perceptions of the world and their physical interactions with it (think of an infant who puts an object in their mouth to explore it). Piaget believed that true thinking, mentally representing the world, was limited or absent. Consider Piaget’sobject 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 hides the toy from view by putting it under a cover and not letting the infant immediately reach for it, the infant is very likely to make no effort to retrieve it (because the infant thinks the toy just disappeared forever, like magic) and show no emotional distress (Piaget, 1954). This is not due to the infant being uninterested in the toy or unable to reach for it; they just think it is no longer there because they can not see 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 even when out of sight (they lack "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). This focus on one dimension is a cognitive limit seen at this age known as "centration". Centration is one reason the preoperational child will fail a conservation task. Another is their inability to mentally reverse. While we can readily reason that the water that looks like more or less in a container of a new shape because we know it came from the original container, the preoperational child lacks that reasoning ability.
Children progress beyond the limits seen in the preoperational stage during theconcrete operational 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 kid believed that weight was the only variable that mattered, that kid might put the heaviest weight on the shortest string and push it the hardest, and then conclude that just as they 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. We will explore Piaget in more detail later.
Although Piaget’s theory has been very influential, it has not gone unchallenged. Many more recent researchers have obtained findings indicating 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.
So, is cognitive development fundamentally continuous or fundamentally discontinuous? A reasonable answer seems to be, “It depends on how you look at it and how often you look.” Thus, the debate between those who emphasize discontinuous, stage-like changes in cognitive development and those who emphasize gradual continuous changes remains a lively one.
Lev Vygotsky (1896-1934) was a Russian psychologist who wrote in the early 1900s but whose work was discovered in the United States in the 1960s but became more widely known in the 1980s. Vygotsky differed with Piaget in that he believed that a person not only has a set of abilities, but also a set of potential abilities that can be realized if given the proper guidance from others. His sociocultural or sociocultural cognitive theory emphasizes the importance of culture and interaction in the development of cognitive abilities. He believed that through guided participation known as scaffolding, with a teacher or capable peer, a child can learn cognitive skills within a certain range known as the zone of proximal development. Have you ever taught a child to perform a task? Maybe it was brushing their teeth or preparing food. Chances are you spoke to them and described what you were doing while you demonstrated the skill and let them work along with you all through the process. You gave them assistance when they seemed to need it, but once they knew what to do-you stood back and let them go. This is called scaffolding and can be seen demonstrated throughout the world. This approach to teaching has also been adopted by educators. Rather than assessing students on what they are doing, they can be understood in terms of what they are capable of doing with the proper guidance. You can see how Vygotsky would be very popular with modern-day educators.
