Story of Psychology - Morton Hunt [232]
Such mental development does not take place smoothly and continuously. From time to time, the accumulation of small changes such as the discovery of commutativity brings about a relatively abrupt shift to a different stage of thinking. The notion that the human psyche develops stage by stage was not original with Piaget—it had been suggested earlier by other psychologists—but Piaget was the first to identify and describe the stages on the basis of a wealth of observational and experimental evidence. The four major stages in Piaget’s theory (there are many substages) are:
—sensorimotor (birth to 18–24 months),
—preoperational (18–24 months to 7 years),
—concrete operations (7 years to 12 years), and
—formal operations (12 years and up).
The ages are only averages; Piaget was well aware that there are individual differences. But he said that the sequence was invariant; each stage is the necessary foundation of the succeeding one.
This is what takes place in each (some of the following findings have been modified by later research, as we will shortly see):12
Sensorimotor (birth to 18–24 months): At first infants are aware only of their sensations and do not connect them with external objects. They do not even connect the images of their hands with the sensations of their hands moving, and only gradually, through trial and error, discover how to make their reaching for a toy coincide with what they see.
Even when their movements become more purposeful and accurate, they have no sense of what the objects around them are like or how those things will respond to their actions. So they experiment: they suck, shake, bang, hit, or throw objects, thereby acquiring new knowledge that leads to more intelligent and purposeful actions.
From such experiences, and with the help of the growing power of memory (in part due to continuing maturation of the brain), children begin to have a store of mental images. This is why they realize, in the latter quarter of the first year, that a hidden object still exists, even though the perception of it is gone. Piaget called this the attainment of “object permanence.”
Toward the end of this stage, children begin to use their stored images and information to solve problems involving physical objects; they think about what might happen, instead of relying solely on manipulating things. Piaget, as a young father, proudly reported an episode of such thinking by his daughter Lucienne, who was sixteen months old. While playing with her, he put a watch chain in an empty matchbox, which he carefully left slightly open. He handed the matchbox to Lucienne, who had not been aware of his opening and closing it and had not seen him put the watch chain in it. She had only two “schemes” (learned ways of dealing with the situation): turning the box upside down to dump out its contents, and pushing her fingers in the slit to bring out the chain. She tried the second procedure first, groping to reach the chain, but was unable to. Then came a pause, during which Lucienne did something odd and noteworthy; as Piaget later reported the event:
She looks at the slit with great attention; then, several times in succession, she opens and shuts her mouth, at first slightly, then wider and wider… [then] unhesitatingly puts her finger in the slit, and instead of trying as before to reach the chain, she pulls so as to enlarge the opening. She succeeds and grasps the chain.13
Children also begin,