Story of Psychology - Morton Hunt [242]
To be sure, there are other candidates for a metatheory that will provide a unified mental science; more of that later. Meanwhile, we have gone far afield from development, to which, after a final word about Piaget, we return.
About Piaget: Many developmentalists, while accepting his general conception of human development, now consider his scheme of stages physiologically limited and culturally biased. A number of modified stage theories have been advanced, but it is unclear which one will eventually dominate the field. Whichever one does, however, it will embody Piaget’s fundamental concepts but go far beyond them, even as Einstein’s physics embodied but went far beyond Newton’s.
Maturation
Despite Piaget’s training in the natural sciences and his early decision to explore the biological explanation of knowledge, his theory deals almost entirely with development through cognitive processes; he either ignores the role of maturation—the growth processes of the body that automatically cause changes in behavior—or takes it for granted. But for some years many developmentalists have felt that until the part that maturation plays in psychological development is fully spelled out, we cannot know to what extent behavior is innate rather than acquired by means of assimilation and accommodation.
Yet how is one to distinguish between the two influences? From the infants’ first day outside the womb they are learning as well as maturing; isolating the results of each process is a scientific problem of the first order. Newborns do, to be sure, possess important reflexes at birth that cannot owe anything to learning, such as turning their head toward a touch on the cheek as if in search of the nipple before they have ever known a nipple. And as most parents know, if you stick out your tongue at infants only one to three weeks old, they reflexively stick out their own tongues, an inherent reaction produced by “mirror neurons” that have recently been identified by brain scans and located as being in the pre-motor cortex. But in general most changes in behavior or new forms of behavior may come either from maturation or learning or both.
Sometimes, however, nature accidentally provides an experiment that separates the two. Infants begin to babble at three or four months as a preparation for speech—but so do deaf children, obviously not in an effort to imitate heard speech but for some other reason. Babbling is evidently a form of programmed behavior that owes nothing to experience but begins spontaneously when the neural centers that direct it reach a certain stage of development. In normal children, babbling changes through learning, coming more and more to resemble the sounds and intonations of speech; in deaf children it slowly disappears from lack of learning.54
Since opportunities to observe behavioral development in the absence of learning are rare, during the early years of the specialty a few developmental psychologists made history by creating the conditions experimentally. In 1932, Myrtle McGraw, then at the Columbia-Presbyterian Medical Center in New York, got a low-income Brooklyn family to lend her their twin boys for an experiment. For two years Johnny and Jimmy, apparently identical twins, spent eight hours a day, five days a week, in McGraw’s laboratory. Johnny got extensive training in physical skills; Jimmy remained in his crib “undisturbed” (not even played with) and with only two toys at a time. Johnny,