"The Invention Of Language By Children: Environmental And
Biological Influences On The Acquisition Of Language"
Language acquisition is a universal phenomenon, because "all normal children acquire their native tongue to a high level of proficiency within a narrow developmental time frame." Why? The explanation of this must lie in biology. "In other words, some part of the capacity to learn langauges must be innate'. At the same time, it is equaly clear that language is `learned'." One issue dealt with by this chapter is an attempt to resolve this conflict.
Basic point: "Language acquisition in humas seems to involve a type of learning that is heavily constrained, or predisposed to follow certain limited courses, by our biology." Innateness reflects deep, underlying similarities among all human languages. The point of the chapter is to review 2 lines of evidence for biological underpinnings of language acquisition: (1) enviromental variability does not affect language learning to any great degree, while (2) child picks up linguistic properties that could not have been in the environment.
"Language learning follows the same course in all of the many languages that have been investigated." By 1 year, isolated words are produced; by 2 years, there is a vocabulary spurt with rudimentary sentences; from 2-5 years language structure is elaborated to include complex multiclausal sentences that include function morphemes; 5 year old language is essentially adult.
All of this implies biological basis for language learning. "Language learning is controlled, at least in part, by some underlying maturational timetable." But these findings are not conclusive, because they might only reflect the fact that children "may go through these regular stages because such stages are the only logical way to learn, through time and exposrue, all the detailed facts about the language that they are hearing from adults around them."
Apporach to rule this out is to show that changing the environment has little effect on the time course of language learning, but that changing the biological "maturational status" of the language learner can have great effects on language learning. Altering The Learning Environment
Variation In Motherese
Question: Does motherese play a causal role in language acquisition? In a nutshell, the answer to this question is NO! First, "contrary to intuition, maternal speech is not characterized by simple declarative sentences of the kind that children utter first." Second, simplicity of mother's language does not predict child's learning rate.
Language Invention By The Isolated Deaf Child
Sign language (ASL) is a full blown natural language, with all of language's abstract structure. "Most deaf infants, though, are born into hearing families in which the parents know no sigh language. In many cases the parents make the decision not to allow the children access to sign language at all." This represents radical environmental variation, because children are deprived of linguistic input.
Amazingly, language's time sequence of development is still evident -- 1 year, produce single manual gestures; "at about age 2, again in common with their hearing peers, the deaf children began to sequence their gestures in rudimentary two- and three-sing sentences, with occasional examples of yet further complexity." While homemade system is ultimately much simpler than would be the case if full linguistic environment is present, its developmental sequence indicates underlying biology.
Language Development In The Blind Child
Vision is an important source of contextual meaning during language learning. So, "the restrictons on blind children's access to contextual information ought to pose acquisitoinal problems. Yet study of their progress demonstrates that there is neither delay nor distortion in their language growth." For example, words describing visual experience, like `look' and `see', are the first verbs to appear in their language -- with meanings adjusted to the sense of blind `looking' with touch.
In sum, changes in environment have little effect on maturation of language. What about changes in biology? Changing The Learner's Mental Endowment
Deprivation Of First Language Exposure Until Late In Life
"If maturation is a serious limiting factor in acquisition, learning should look different if it takes place later in life than in the usual case: Presentation of a full and complete environment for language learning, but at a time after the usual matrualtional sequence should have been completed, would on this view not result in normal acquisition."
E.g of this -- feral children. Isabelle did acquire language, but Genie and Chelsea did not. "Why did Genie and Chelsea not progress to full language knowledge while Isabelle did? The best guess is that the crucial factor is the age at which exposure to linguistic stimulation began. Age 6 (as in Isabelle's case) is late, but evidently not too late. AGe 13 or 31 is too late by far." Bottom line: biology determines a critical period for learning. But it is premature to make this claim without converging evidence.
Second Language Learning
What about learning a second language later in life? Early on, adults are more efficient, but "the long-range outcome is just the reverse. AFter a few years very young children speak the new language fluently and sound just like natives. This is highly uncommon in adults." The later the exposure to the second language, the poorer are the expected results of language learning.
Late Exposure To A First Language
Another example is first language exposure late in life. There are many ASL instances of this, and again evidence for a critical period is found. "After thirty years or more of exposrue and constant use, only those who had been exposed to ASL before age 6 showed native-level fluency.
Pidgins And Creoles
Pidgin is used in communiteis that must communicate across language barriers. Children exposed to pidgin-speaking parents develop a creole language, which "undergoes rapid change and expansion of just the sort one might expect based on the learning data we have presented so far." Similar results from "pidgin ASL" exposure.
Focus so far has been on data from unusual language learning situations. "These findings point to a human `linguistic nature' that rescues learners from inadequacies in relevant nurture." But such evidence is not necessary. "For every learner of a human langague, no matter how fortunately circumstanced, is really in the same boat as, say, the blind child or the learner exposed to a rudimentary contract language: isolated from much of the information required to learn a langauge from mere exposure.
I.e., language learning is always a difficult induction problem given the stimulus information that the learner is provided. Good example of this is learning meaning of vocabulary words. "All in all, it seems that the word learner is `isolated' from direct informaiton aobut word meanings, even under optimal environmental conditions." Basic point: poverty of the stimulus affects every language learner. (NB: This moves to the second line of evidence, because in essence the poverty of the stimulus argument is interesting because (1) children go beyond the stimulus in terms of what they learn, and/or (2) children require innate, internal constraints to solve this problem which underdetermines their ability to learn language.) "How could a child learn that the principles of English syntax are -- always as it turns out -- structure-dependemnt rather than serial order dependent? ... The solution seems to be that learners are innately biased to assume that generalizations in natural langauges will always be structure-dependent rather than serial-order-dependent."
"To a surprising degree, language is the product of the young human brain, such that virtually any exposure conditions short of total isolation and vicious mistreatment will suffice to bring it forth in every child." Universality of language is a central cognitive property. Of course, the environment does play a role. "What we have tried to emphasize, however, is that acknowledgment of significant environmentally caused variation should not blind us to the pervasive commonalities among all languages and among all their learners."
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