Language acquisition

Language acquisition is the process by which language develops in humans. First language acquisition concerns the development of language in children, while second language acquisition focuses on language development in adults as well. Historically, theories and theorists may have emphasized either nature or nurture as the most important explanatory factor for acquisition.

Most researchers however, acknowledge the importance of both biology and environment. One hotly debated issue is whether the biological contribution includes language-specific capacities, often described as Universal Grammar. For fifty years, linguist Noam Chomsky and before his death Eric Lenneberg, strongly argued for the hypothesis that children have innate, language-specific abilities that facilitate and constrain language learning.

Other researchers, including Elizabeth Bates, Catherine Snow, and Michael Tomasello, have hypothesized that language learning results only from general cognitive abilities and the interaction between learners and their surrounding communities. Recent non-nativist work by William O'Grady proposes that complex syntactic phenomena result from an efficiency-driven, linear computational system. One of the most important advances in the study of language acquisition was the creation of the CHILDES database.

Nativist theories
Linguistic theories hold that children learn through their natural ability to organize the laws of language, but cannot fully utilize this talent without the presence of other humans. This does not mean, however, that the child requires formal teaching of any sort. Chomsky claims that children are born with a hard-wired language acquisition device (LAD) in their brains. They are born with the major principles of language in place, but with many parameters to set (such as whether sentences in the language(s) they are to acquire must have explicit subjects). According to nativist theory, when the young child is exposed to a language, their LAD makes it possible for them to set the parameters and deduce the grammatical principles, because the principles are innate.

Mark Baker's work, The Atoms of Language (2004) presents arguments that there are not only certain "parameters" (as Chomsky called them) that are innate switches in our LAD, but we are very close to the point where these parameters could be put together in a "periodic table of languages" as determined by their parameter features. Baker's work is very controversial, however, because he has argued (1996: 496-515) that principles and parameters do not have biological or sociological origins, but instead were created by God (i.e. creationism). In contrast to Baker's theological creationism, Chomsky, although not a creationist has been described as a magical creationist or a crypto-creationist (e.g. MacFarquhar, 2003: 71) by people who find his scepticism of natural selection troubling. Chomsky does however make it clear in a reply to John Maynard Smith that he does believe that the innate capacity for language can be explained by biology when he states that language "... can be studied in the manner of other biological systems.".

In addition, there are significant studies in biogenetics that strongly suggest that the genetic factors that combine to build the brain contain redundant systems for recognizing patterns of both sight and sound.

One idea central to the Chomskian view is the idea of Universal Grammar, which posits that all languages have the same basic underlying structure, and that specific languages have rules that transform these underlying structures into the specific patterns found in given languages. This is important in 20th Century philosophy because it directly counters Wittgenstein's key assertion that grammar is just surface and arbitrary, like the rules of a chess game.

Another Chomsky argument is that without a propensity for language, human infants would be unable to learn such complete speech patterns in a natural human environment where complete sentences are the exception. This is sometimes mischaracterised as the poverty of the stimulus argument. Psychologists such as Catherine Snow at Harvard, who study parent-child interaction, point out that children do not have to deduce the principles of language from impoverished and ungrammatical scraps of talk. Many studies of child directed speech or CDS have shown that speech to young children is slow, clear, grammatical, and very repetitious, rather like traditional language lessons.'

Non-nativist theories
Non-nativist theories include the Competition model and Social interactionism. Social-interactionists, like Snow, theorize that adults play an important part in children's language acquisition. However, some researchers claim that the empirical data on which theories of social interactionism are based have often been over-representative of middle class American and European parent-child interactions. Various anthropological studies of other human cultures, as well as anecdotal evidence from western families, suggests rather that many, if not the majority, of the world's children are not spoken to in a manner akin to traditional language lessons, but nevertheless grow up to be fully fluent language users. Many researchers now take this into account in their analyses. Furthermore, as any parent knows, children often pay scarce attention to what they are told to say, instead sticking to their own ungrammatical preferences.

Nevertheless, Snow's criticisms might be powerful against Chomsky's argument, if the argument from the poverty of stimulus were indeed an argument about degenerate stimulus, but it is not. The argument from the poverty of stimulus is that there are principles of grammar that cannot be learned on the basis of positive input alone, however complete and grammatical that evidence is. This argument is not vulnerable to objection based on evidence from interaction studies such as Snow's.

However, a powerful argument against Chomskian views of language acquisition lies in Chomskian theory itself. The theory has several hypothetical constructs, such as movement, empty categories, complex underlying structures, and strict binary branching, that cannot possibly be acquired from any amount of input. Since the theory is, in essence, unlearnably complex, then it must be innate. A different theory of language, however, may yield different conclusions. Examples of alternative theories that do not utilize movement and empty categories are HPSG and Construction Grammar. While all theories of language acquisition posit some degree of innateness, a less convoluted theory might involve less innate structure and more learning. Under such a theory of grammar, the input, combined with both general and language-specific learning capacities, might be sufficient for acquisition.

The Critical Period Hypothesis
Linguist Eric Lenneberg (1964) stated that the crucial period of language acquisition ends around the age of 12 years. He claimed that if no language is learned before then, it could never be learned in a normal and fully functional sense. This was called as the "Critical period Hypothesis."

An interesting example of this is the case of Genie, also known as "The Wild Child". A thirteen-year-old victim of lifelong child abuse, Genie was discovered in her home on November 4th, 1970, strapped to a potty chair and wearing diapers. She appeared to be entirely without language. Her father had judged her retarded at birth and had chosen to isolate her, and so she had remained up there until her discovery.

It was an ideal (albeit horrifying) opportunity to test the theory that a nurturing environment could somehow make up for a total lack of language past the age of 12. She was unable to acquire language completely, although the degree to which she acquired language is disputed. Due to this and other complications, she eventually ended up in an adult foster care home.

Detractors of the "Critical Period Hypothesis" point out that in this example and others like it (see Feral children), the child is hardly growing up in a nurturing environment, and that the lack of language acquisition in later life may be due to the results of a generally abusive environment rather than being specifically due to a lack of exposure to language.

The current, up-to-date ideas about the Critical Period Hypothesis are represented by the University of Maryland, College Park instructor Robert DeKeyser. DeKeyser argues that although it is true that there is a critical period, this does not mean that adults cannot learn a second language perfectly. DeKeyser talks about the role of language aptitude as opposed to the critical period.

Additional arguments for nativism
However, there exists emerging evidence of both innateness of language and the "Critical Period Hypothesis" from the deaf population of Nicaragua. Until approximately 1986, Nicaragua had neither education nor a formalized sign language for the deaf. As Nicaraguans attempted to rectify the situation, they discovered that children past a certain age had difficulty learning any language. Additionally, the adults observed that the younger children were using gestures unknown to them to communicate with each other. They invited Judy Kegl, an American linguist from MIT, to help unravel this mystery. Kegl discovered that these children had developed their own, distinct, Nicaraguan Sign Language with its own rules of "sign-phonology" and syntax. She also discovered some 300 adults who, despite being raised in otherwise healthy environments, had never acquired language, and turned out to be incapable of learning language in any meaningful sense. While it was possible to teach vocabulary, these individuals seem to be unable to learn syntax.

The developmental period of most efficient language learning coincides with the time of rapid post-natal brain growth and plasticity in both humans and chimpanzees. Prolonged post-natal brain growth in humans allows for an extended period of the type of brain plasticity characteristic of juvenile primates and an extended time window for language learning. The neotenic pattern of human brain development is associated with persistence of considerable language learning capacity into human adulthood.

Derek Bickerton's (1981) landmark work with Hawaiian pidgin speakers studied immigrant populations where first-generation parents spoke highly-ungrammatical "pidgin English". Their children, it was found, grew up speaking a grammatically rich language -- neither English nor the broken pidgin of their parents. Furthermore, the language exhibited many of the underlying grammatical features of many other natural languages. The language became "creolized," and is known as Hawaii Creole English. This was taken as powerful evidence for children's innate grammar module.