Language development

Human infants are acutely attuned to the human voice, and prefer it above all other sounds. In fact, they prefer the higher pitch ranges characteristic of female voices. They are also attentive to the human face, particularly the eyes, which they stare at even more if the face is talking. These preferences are present at birth , and some research indicates that babies even listen to their mother's voice during the last few months of pregnancy. Babies who were read to by their mothers while in the womb showed the abilityto pick out her voice from among other female voices.

 Infancy

Since the early 1970s, it has been known that babies can detect very subtle differences between English phonemes (the functional units of speech sound). For example, they can detect the difference between "pa" and "ba," or between "da" and "ga." Of course, they do not attach meaning to the differences for 12 months or more. The original technique of investigating this capacity capitalized on babies' innate ability to suck on a nipple. The nipple is linked to a device that delivers sound contingent on the baby's sucking. Babies introduced to this device suck vigorously to hear the sound, even when it is a repetitive "ba ba ba ba." Because babies also get bored with repetition, they stop sucking hard after a few minutes. At that point the researcher can change the sound in subtle ways, and see if the baby shows renewed interest. For example, it might be a different example of "ba," perhaps one with a bit more breathiness. Or, it could play a sound that would fall into a new phoneme class for adults, like "pa." Babies ignore the first kind of change, just as adults would, but they suck with new vigor for the new phoneme.Babies have finely tuned perception when it comes to speech sounds, and, more importantly, they seem to classify many sounds the same way adult speakers would, a phenomenon known as categorical perception . These sounds that they perceive as indivisible categories are generally those that form the basis for many speech systems in the world's languages, rather than those that are used only rarely, like "th." Infants come into the world already predisposed to make certain distinctions and classifications: apparently they are not driven to make them by language exposure

Babbling

At the beginning of infancy , vegetative noises and crying predominate. Observers note that by the age of four months, the baby's repertoire has expanded in more interesting ways. By this point babies are smiling at caregivers and in doing so they engage in a cooing noise that is irresistible to most parents. When the baby is being fed or changed, she will frequently lock gazes with her caregiver and coo in a pleasant way, often making noises that sound like "hi," and gurgles. It is common for the caregiver to respond by echoing these noises, thereby creating an elaborate interchange that can last many minutes. This may not happen universally, however, as not all cultures take the baby's vocalization so seriously. The nature of the sounds made at this stage is not fully speech-like, though there are open mouth noises like vowels, and an occasional "closure" akin to a consonant, but without the full properties that normally make a syllable out of the two.

At some point between four and 10 months, the infant begins producing more speech-like syllables, with a full resonant vowel and an appropriate "closure" of the stream of sound, approaching a true consonant

This stage is called "canonical babbling."

Toddlerhood

The first words make their appearance any time between nine and 15 months or so, depending on the child's precocity and the parent's enthusiasm in noticing. That is, the baby begins making sounds that occur fairly

Reliably in some situations AND are at least a vague approximation to an adult-sounding word.

What the baby "means" by these sounds is questionable at first. But before long, the baby uses the sounds to draw a caregiver's attention, and persists until she gets it, or uses a sound to demand an object, and persists until it is given to her. At this point the first words are being used communicatively as well. There is a fairly protracted period for most babies in which their first words come and go, as if there is a "word of the week" that replaces those gone before. One of the characteristics about these first words is that they may be situation-specific, such as the case of a child who says "car" only when looking down on the roofs of cars from her balcony. But after several months of slow growth, there is an explosion of new words, often called the "word spurt." This usually coincides with an interest in what things are called, e.g., the child asking some variant of "What's that?" Vocabulary climbs precipitously from then on—an estimated nine new words a day from ages 2 to 18 years. These developments are noted in all the cultures that have been studied to date

Word meanings

The meanings of the child's first words are not necessarily the same as those of the adults around her. For instance, children may "overgeneralize" their first words to refer to items beyond their usual scope of application. A child might call all men "Daddy," or all animals "doggie," or all round objects "ball." Others have pointed out that "undergeneralization" also occurs, though it is less likely to be noticed. For instance, a child might call only her own striped ball "ball," and stay silent about all the rest, or refer to the family dog and others of the same type as "doggie" but not name any others. The child may also use a word to refer to a wide variety of objects that hold no single property in common. A child who learned "moon" for the full moon later used it for street lamps, house lights (lights in common), doorknobs and the dial on the dishwasher (shape in common), and toenail clippings on a rug (related shape). Put into a class, these objects share nothing in common except a shifting form of resemblance to the original moon,

Preschool years: the two-year-old

Grammar: the two-word utterance

The first sentence is the transition that separates humans from other creatures. Most toddlers produce their first spontaneous two-word sentence at 18 to 24 months, usually once they have acquired between 50 and 500 words. Before their first sentence, they often achieve the effect of complex expressions by stringing together their simple words:

Book

Mine

Read

Then their first sentence puts these words under a single intonational envelope, with no pause. Their first sentences are not profound, but they represent a major advance in the expression of meaning.

Semantic relations

Most studies on early child language conclude that the child at the two-word stage is concerned with the expression of a small set of semantic relationships. The cross-linguistic study of children includes languages as remotely related as French, Samoan, Luo (spoken in Kenya), German, Finnish, and Cakchiquel (a Mayan language spoken in Guatemala). Two-yearold children learning all these languages expressed only a narrow range of the possible meanings that the adult language could express. All over the world, children apparently talk about the same meanings—or ideas—in their first sentences, despite the variety of forms in those languages. For example, the children refer to possession (Mommy dish, my coat), action-object sequences (hit ball, drop fork), attribute of an object (big truck, wet pants) or an object's location (cup shelf, teddy bed).