Early Theories of Cognitive Development in Childhood
In 1954 Swiss psychologist Jean Piaget observed that children do not think like adults. He developed a theory of cognitive development rooted in observations of his own children. Piaget believed cognitive development begins with the sensorimotor stage (birth to two years of age), during which infants are aware only of sensations and their own movements. By exploring the world, they develop schemas (theories) about the way the world works. They integrate new information learned from experience into their existing understanding of the world in a process called assimilation. They modify or create new theories as a result of experience in a process called accommodation. Infants begin life with no concept of object permanence, the understanding that objects continue to exist even when they are out of sight. Piaget believed that object permanence emerged at about nine months of age.
According to Piaget, at around two years of age, children enter the preoperational stage (two to seven years of age) during which they develop a preliminary understanding of the physical world. Young children lack the concept of conservation, the understanding that the quantitative (quantity-related) properties of an object are constant despite changes in the object's appearance. For example, when children are shown two equal sets of objects (e.g., coins or cups) arranged in two rows, they agree the objects are equal in number. But when the objects in one row are spread apart to make the row longer, children claim that the longer row has more objects. Preoperational children also show marked egocentrism, a developmentally normal failure to understand that other people differ in their knowledge and perspectives. When children begin to tell lies, this shows an emerging understanding that they may have knowledge other people do not share.
In the next stage of development, called the concrete operational stage (7 to 11 years of age), children come to understand which actions can or cannot affect concrete objects. They can understand math that has clear links to the world of objects, such as adding or multiplying. In the fourth and final stage, the formal operational stage (age 11 and beyond), children acquire the capacity to reason about abstract concepts. During this stage they become capable of complex mathematical reasoning. They also become able to evaluate abstract ideas such as freedom or justice.
Piaget’s Stages of Cognitive Development
|Sensorimotor||0–2 years||Experiences the world through senses and actions|
|Preoperational||2–7 years||Represents things with words and images; uses intuition rather than logic|
|Concrete operational||7–11 years||Thinks logically about concrete events; can understand and make analogies|
|Formal operational||11+ years||Uses hypothetical and abstract reasoning|
Modern Perspectives on Cognitive Development
Violation of Expectation Experiment
According to Piaget, preoperational children fail to understand that other people may possess different preferences than they do due to an egocentric way of thinking. Yet when asked to select food to give to other people, toddlers choose foods they know the other person prefers, even if they do not like that food themselves. Piaget also claimed that until 9 or 10 years of age, children had great difficulty with perspective-taking (i.e., judging what a scene looks like from another person's point of view), yet more recent research has demonstrated this ability in children as young as four years of age.
Some of the most compelling results in developmental research come from work on theory of mind, the ability to attribute mental states (such as beliefs, desires, and knowledge) to others and to reflect on one's own mental states. Early work indicated that this ability does not emerge until the fourth or fifth year of life. This research was based on variations of the false-belief task, which was initially explored by psychologists Heinz Wimmer and Josef Perner at the University of Salzburg, Austria, in 1983. In this task, a child watches as a puppet places an object (e.g., chocolate) in a container and then leaves. A second puppet then moves the chocolate to a different location. When the first puppet returns, the child is asked where the puppet will look for the object. Children older than about five years of age say the puppet will look where the object was originally placed. But younger children say the puppet will look in the new location for the object. Using the violation of expectation and looking time paradigms, children as young as 15 months show surprise and look longer when the puppet looks in the new location rather than the original location. This means they expect the puppet to still believe the object is where it was originally put, not where the infant knows the object actually is.
Adolescent and Adult Cognitive Development
Brain maturation continues through the early- to mid-20s. There is a marked increase in the rate of growth in nerve tissue just before puberty that improves communication among different brain regions, such as those involved in language and spatial reasoning. These changes greatly benefit abstract reasoning.
By contrast, the prefrontal cortex undergoes significant neural pruning (removal of connections) rather than growth. Two-year-olds have about 15,000 synaptic connections in this region. By the end of adolescence, fewer than half of those connections remain as infrequently used connections are eliminated. The prefrontal cortex is involved in skills such as reasoning and behavioral control. Because this process of brain wiring and pruning is not complete until the beginning of the second decade of life, adolescence is a time of improved abstract reasoning but faulty decision-making.
Researchers have studied older adults in disciplines as diverse as chess, typing, and plane piloting. In each case, older adults respond more slowly and show poorer memory for new memories formed outside their areas of expertise. However, they rival much younger adults in speed and accuracy when executing skills within their areas of expertise and on memory tests involving information about which they are experts. This happens because the aging brain becomes less differentiated (more brain areas are involved in completing tasks). The brains of younger adults are highly differentiated in that different regions of the brain are specialized in performing specific mental tasks. In the brains of older adults, differentiation decreases as multiple areas of the brain are recruited to aid in performance.