Language learning by adults (the so-called "second language acquisition")
During childhood, language acquisition is a natural consequence of prolonged exposure to a language. A spoken language need not be formally taught to a child in order to be learned. (By contrast, written language must always be taught.) Any small child will acquire native fluency in any language if exposed to it on a consistent basis in a social setting. A child will naturally acquire native fluency in more than one language under these circumstances.
In the overwhelming majority of individuals, however, this natural ability to acquire spoken language without deliberate effort begins to diminish sharply at about the age of puberty (12-14 years of age). Teenagers exposed to a new language after this age will acquire it with definite interference from whatever language or languages they had been exposed to before puberty. Language acquisition by adults is language learning--a deliberate, painstaking, intellectual process that rarely, if ever, results in the total native fluency acquired so naturally by any small child, regardless of intellectual ability or personal motivation. The deficiency is particularly evident at the phonetic level, and adults who learn second languages usually speak them with some recognizable non-native accent. Thus, language acquisition by children and language learning by adults are strikingly different phenomena. What accounts for this difference?
Today we will talk about language learning by adults (post puberty individuals), a process usually called second language acquisition. But this term is misleading. Some people think that it is the presence of a first language that caused the difficulty. This is not true. Before puberty, young children can acquire second and third languages with equal ease and fluency, although they will forget them just as quickly if they cease to be exposed to them in childhood. Also, a child who never acquires a first language will still have problems acquiring a language after puberty (cf. the story of Genie, an abused child found by social workers at about age 13 1/2 who had never been spoken to and had no first language at all). So the presence of one language is actually not the critical factor that slows down a person's ability to acquire other languages. Instead, the crucial factor seems to be the age and maturation of the individual: a person before puberty acquires language naturally, while the same person after puberty must learn the language with great effort that yields less than perfect results.
Why the link with puberty? Is it simply coincidence? We don't know whether the two phenomena of onset of adult sexual characteristics and dimunition of child-like language acquisition skills is coincidental or interdependent. It is suspected that some change in the structure of the brain that occurs at puberty also reduces language learning ability. Whatever the case, the dimunition of language acquisition ability is probably the consequence of an evolutionary adaptation. The brain is a greedy organ, using a great deal of energy. It is assumed that a larger portion of the neural capacity in a child's brain is structured to participate in the acquisition of language. Later, most of those neurons are rerouted for other uses. By puberty, the language function becomes localized in specific areas of the brain. This course of maturation probably developed during the many tens of thousands of years that humans lived in small bands of hunter-gatherers--and adult language learning was not generally essential to the welfare and survival of the group.
No one can prove this, of course, and no one has isolated exactly what neural changes in the brain cause child language acquisition to be replaced by adult language learning. But there is one hypothesis that attempts to describe the mechanism which reduces language acquisition ability in the adolescent.
Let's reexamine the period of change between child language acquisition and the need for adult language learning. The critical age hypothesis of language acquisition. Biologists studying the origin of species-specific behavior (rats, goslings), have noted that there were periods when a particular kind of stimulus is needed to be present if the fledgling was to develop normally. American psycholinguist Eric Lenneberg (1921-1975) argued that such a critical period also exists for human language acquisition. He put forward the critical age hypothesis: changes in language acquisition ability are linked to stages in brain maturation. Studies have shown that beginning at about age 2, language skills begin to be localized in the left hemisphere of the brain (the Broca's and Wernicke's areas to be discussed next week). This process, known as lateralization, seems to be completed at about the time of puberty. This hypothesis based on evidence from studying adults who suffer brain damage that results in language loss, or aphasia. If the damage is mild, adults who suffer such brain damage may regain their language facilities quickly; but in cases of more severe damage, part or all of the language ability is lost forever. In small children, however, even severe aphasia is more likely to be gradually reversed, with language becoming localized or relocalized in the right hemisphere of the brain. Recovery is even possible for children in cases where the entire left hemisphere is surgically removed. For most adults, on the other hand, losing the left hemisphere would mean the permanent loss of language.
Problems with the critical age hypothesis.
1) Children do not always recover from aphasia either. Why doesn't relateralization take place in all cases of pre-puberty brain injury?
2) More recent neurological studies indicate that much of brain lateralization takes place long before puberty. But proponents of the critical age hypothesis argue that lateralization is not fully established until the age of puberty.
Another way to test the hypothesis: Children deprived of social interaction necessary for language learning: first exposure to language being after the critical age. 200 or more cases of the so-called 'wolf children' --raised by animals. Most legendary or poorly documented:
A famous case: Wild boy of Aveyron. Found running wild in woods of France in 1800. Taken to psychologist-- couldn't speak although he had perfect hearing--11 or 12 when found never learned to speak. May have been retarded-- too little is known.
Another famous case: 1970- Genie, 13 1/2 year-old girl, confined to a room and never spoken to. Knew only a few words and rudimentary commands. Later learned English from exposure to speech in a foster home. Learned to communicate in English but still had trouble with certain phonetic combinations. Difficulty in asking questions and in using deictic area of speech. Studies showed that the right side of her brain, not the left, controlled language, which would support the critical age hypothesis.
We have seen that all small children are equally excellent language learners. Russian children's writer Kornei Chukovsky sees them as truly creative at this stage: "beginning with the age of two, every child becomes for a short period of time a linguistic virtuoso. Later, beginning with the age of five or six, this talent begins to fade." It recedes drastically after the onset of puberty.
Differences in adult language aptitude
Although every child, regardless of intellectual level, is equally gifted at acquiring language, it does not seem to be the case with adults. Some adults can learn a second language with something close to native fluency; others will retain a distinct foreign accent even after decades of practice. Do some adults possess a special aptitude for learning languages after the critical age? Probably yes: although any adult can learn a second language, not all will do so with equal results (unlike the case with child language acquisition). Adult language learning ability seems to involve a type of talent, or set of talents. What are these talents that can partly mimic childlike facility with language?
Differences in adult ability to master the grammar of a second language seem only in part connected to individual differences in general intelligence; the ability to learn languages in adulthood seems to be a talent apart from what we usually label as general intelligence. In fact, some adults who are seriously learning impaired have almost childlike abilities to master languages (General Eisenhower's translator was a man of very meager mental abilities who was fluent in 44 languages and acquired new ones very quickly.) Adult language learning aptitude seems to be a separate ability, like musical or artistic talent.
Differences in adult abilities to learn languages are even more apparent at the phonetic level: some adults have a natural talent for imitating the voices of other people; other adults do not have this talent at all. This talent for phonetic mimicry in adults definitely does not depend on general intelligence. People of very limited intellectual abilities sometimes have amazing abilities to imitate people's voices (cf. the Truman Capote story Johnny Bear, about an idiot savant with amazing mimicry ability.)
What other individual factors come into play? Exceptional memory in some adults seems to be another factor that assists greatly in second language learning. Memory is also in part an inborn talent separate from general intelligence. Most people who learn several languages during the course of their lifetime forget all but the ones they use. Old languages become dormant as new ones are learned. Only a few individuals are able to acquire and retain fluency in many languages. Charles Berlitz was said to be fluent in several dozen languages. Guiseppe Mezzofanti, librarian at the Vatican who lived from 1774-1849 was said to speak 50 languages fluently and be able to translate several more. But even these gifted individuals learned languages by studying them deliberately; they didn't really acquire them effortlessly as children do. They had to teach themselves language--or pay careful attention when being taught by others.
Although there does seem to be differences in the ability of individual adults to learn a second language, any adult of reasonable abilities, if given enough time, enough opportunity, and--most importantly--having enough desire, can learn to communicate in any language. But the degree of eventual fluency achieved will differ considerably from individual to individual, unlike the situation with child language acquisition (where every child achieves perfect fluency given enough exposure). Successful adult language learners usually learn language through conscious effort--deliberate learning-- rather than acquire it passively without a significant amount of deliberate intellectual effort as do children. Motivation is an important factor in language learning, and societies that praise or emphasize the value of multilingualism will increase the motivation level of learners and thus increase the success of second language learning in general--Hungary being a case in point (since Hungarian is so unlike all of the surrounding European languages, that small country has encouraged multilingualism.)
Since language acquisition in adults is really language learning, how does one go about teaching a second language to an adult? Various philosophies exist regarding adult language learning and teaching. Probably, no single philosophy or method is universally best for all teachers and learners. Each approach has made positive contributions to language teaching; and each one can be negative and limiting if carried to an extreme.
Let's look at two well-known philosophies and approaches to language teaching.
1. Contrastive hypothesis: the structure of the first language is viewed as a powerful linguistic helping device and becomes the main vehicle for the learning of a second language.
Audio-lingual method (from the Behaviorist School). Language is stimulus and response and is best learned by rote. The Russians say, Povtorenie mat' uchenia, or "Repetition is the mother of learning." Emphasis is placed on testing, direct correction. Grammar discussed in the native language of the student.
Criticism: Students taught exclusively in this way are not prepared to use the language in a natural setting. Ignores (some would say stifles) creative aspect of language. Artificial way to learn language (but, of course, for biological reasons, all adult language learning is artificial when compared to child language acquisition).
2. Identity hypothesis: tries to minimize the difference between first and second language acquisition. Exposure to language will bring about good results--and immersion in the language will bring about the best results.
Natural approach--(since the 60's) tries to approximate the environment that language would be learned as a child. Use of target language in class as much as possible, use of realia and play acting, attempt to make the learner feel at ease and not under pressure to perform, de-emphasizes direct correction.
Part of language learning success depends upon the psychological capacity to take on a new linguistic identity, having a childlike lack of bias to new languages.
Natural approach is best at the most basic stages of language learning, to bring out what childlike abilities are still in the adult.
Criticism: Using the natural approach alone cannot convey all the subtlety of human language or the complexity of the grammar. Some deliberate intellectual approach must supplement it, such as grammatical explanations and structured drills and exercises.
A compromise philosophy of language emphasizes learner differences. There is no single, best way to teach language, because there is no single type of learner. Some students require a more formal presentation to learn the language thoroughly; others can acquire more through less structured immersion in the language.
Whatever methods are employed, the most important tools for adult language learners is determination and consistency, as well as exposure to the proper language form.