Mental Development in the Infant

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The infant's ability to produce sounds is in part anatomical. Initially, the infant's larynx (voice box) is positioned high in his throat, which permits him to breath and ingest milk from a nipple at the same time. Yet this high placement of the larynx also makes it impossible for the infant to articulate the range of sounds found in human languages. (The high placement of the larynx is characteristic of the higher apes and explains why researchers have been able to teach these animals to sign but not to vocalize.) During the first year, the larynx descends into the throat, and the infant is able to progressively articulate more sounds.

Because of the initial high placement of the larynx, the infant's initial sounds are often mewing and throaty. Between the ages of three and nine months, the k and g sounds are very common. This helps to explain why adults, in imitation, often say coo or goo to babies. Later in the first year of life, as babbling comes into play, the early g and k sounds are less prominent as the larynx drops and these sounds become less easy to produce. Once the larynx has moved down into the throat, the infant begins to babble. In the course of this babbling, the infant is likely to produce all of the phonemes—the basic sounds—of his language.

The importance of this early babbling for language acquisition has been demonstrated by recent studies of children who have had their vocal apparatus obstructed by the necessity of a breathing tube in their throats. Their inability to babble during the early months of life delayed not only their acquisition of correct articulation, but also their mastery of other expressive language skills. Because babbling is often a repetitive, rhythmic activity, it has been related to motor development. That is to say, some investigators have found that there is a correlation between motor development and linguistic development. The earlier a child walks, the earlier he is likely to talk. Other investigators, however, find that compensation, not correlation, is the rule. They report that children who walk early, talk late, and vice versa.

Current neurological research suggests that the relation between motor development and language development is more complex than the notion of either correlation or compensation suggests. Brain function is extraordinarily diversified and intricate. Many highly specialized functions combine to form more general functions in a number of different ways. Both language and motor development are linked to brain development, but the interconnections between these developments remain obscure. Put differently, there is no simple relation between motor development and language development, and all sorts of combinations can and do occur.

We can, however, describe the general course of language development. This development involves not only the growing ability to articulate sounds, but also the ability to express meaning and to comprehend the language of others. The babbling that infants engage in during the second half of the first year of life contributes to both of these achievements. First of all, infant babbling is a way of practicing and perfecting the production of speech sounds. Initially, the infant produces many more sounds than those of his native language. Gradually, through hearing adult speech and through being rewarded for making certain sounds that elate parents (like mama or dada), he begins to limit speech production to the sounds of his particular language environment.