language development

n. The acquisition of phonology, morphology, lexicon, syntax, semantics, and pragmatics of a language. Passive exposure to sounds and language begins before birth, while the baby is still in utero. Immediately after birth, infants become exposed to language more directly, as caregivers begin to interact with them and as they hear language sounds or see signing. From very early on, babies learn to detect regularities in patterns of the language to which they are exposed. While healthy human infants are born with the ability to perceive and produce the sounds of all languages, over the course of the first year of life their linguistic system becomes fine-tuned to the structure of the language around them, laying the foundation for native-language learning.

Infants begin to engage in communication early on, initially by crying as they learn to express their needs. Language production develops with babies beginning to coo and then, by the age of 6 months, to babble. In the second half of the first year, the babble turns into nonsense speech that often has the rhythm and sound of language but does not include real words. On average, children are able to produce one or two words by their first birthday, although some children may take a little longer to utter their first word, while children with precocious language abilities often have larger vocabularies at that age. Through their first years of life, children are able to understand more words than they can produce. By 18 months, the average toddler can say 8 to 10 words. By their second birthday, children start putting two or more words together to form simple sentences, such as "more cookie" or "no milk." Researchers who study language development look at children’s mean length of utterance to measure how many meaningful units of language a child can string together.

Children's vocabularies grow rapidly between the second and fifth birthdays, as their brains develop and mature and as they continue to explore their environment. By the time children enter kindergarten, they can already produce declarative, interrogative, exclamatory, and imperative sentences, and many can recognize some letters of the alphabet. Between the ages of 5 and 8, children typically acquire written language and learn to read and write. Language development continues through school age, with children continuously acquiring new words, learning to form increasingly complex sentences, and becoming experts at pragmatic aspects of language use.

Adults continue to hone their language skills throughout the life span, and many go on to learn second, third, or more languages. It is estimated that the majority of the world population is bilingual, trilingual, or multilingual, with individuals successfully acquiring more than one spoken and/or signed language to communicate. Although it is possible to acquire another language at any age, acquisition of a language later in life frequently results in accented speech and in difficulty distinguishing certain sounds, because the articulation and phonological systems are already fully developed and less malleable by new input. Some believe that children who have not been exposed to language prior to reaching puberty will fail to learn language, but the existence of such a critical period is difficult to test empirically since depriving a child of language input is unethical (and the documented cases of feral and isolated children are confounded by other factors).

In general, it is well accepted that language development is shaped by both innate and experiential influences, although the extent to which nature and nurture each contribute to language acquisition remains heatedly debated. On the one hand, language abilities seem to develop best in environments that are stimulating, rich in linguistic input, and full of opportunities to interact with other language users. On the other hand, environmental variables alone cannot account for many of the individual differences, nor for many of the universals observed in language development. One way to study the nativist and interactionist accounts of human language development is by studying the ability of other species to acquire language; research in this area is ongoing. Another way to gain insight into language development is by studying language change as a result of language interaction, for instance, in creole and pidgin languages and in dialects.

Healthy individuals do not normally lose language abilities later in life. However, when associated with medical conditions such as aphasia or dementia, aging can result in loss of language abilities and in difficulty communicating. Intervention approaches developed for remediation of speech and language problems are provided by trained speech- language pathologists and are aimed at individuals with medical conditions, as well as at children acquiring language outside the normal language-development spectrum. Other professionals who study language development include psychologists, linguists, psycholinguists, educators, and communication sciences specialists.

- VM