PROCESSING KNOWLEDGE Input
M, Nvelar
8.4 Conclusions
The first year prepares children for first words and beyond. During a child’s first twelve months, they categorize sound immediately and can even
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detect speech distinctions corresponding to contrasts which do not exist in their native language. “[T]he most important factor controlling the young infant’s . . . speech . . . appears to be a basic set of innate perceptual mechanisms rather than exposure to specific types of early linguistic experience” (Aslin, Pisoni and Jusczyk 1983 and 1998, 642). The wide array of non-native and native sound distinctions of which infants are capable (appendix 2b) has suggested that:
39. a. “[I]nfants can without prior exposure discriminate contrasts relevant to any particular language” (Trehub 1976).
b. They initially “discriminate many, if not all, phonetic contrasts regardless of the linguistic environment in which they are reared” (Kuhl 1987a).
Although it is not yet possible to identify a universal phonetic repertoire with a universal set of category boundaries which subsequently get extended or reduced in an individual language,37 we can conclude that infants appear to be prepro- grammed to distinguish sound variations along every major dimension of speech- sound variation which any language of the world may potentially involve. These facts provide a basis for solution of the problem of language acquisition raised in chapter 3: infants do not need to search the speech stream to perceive acous- tic invariants and thereby discover units. Categorical perception allows them to assign units immediately.
Both speech perception and production reveal continuous linguistic mapping to the phonology of the language being acquired, and developments of percep- tion and production are linked. Effects of the language-specific target on both are first detected about six months. Sensitivity to general prosodic properties of the language, evidenced shortly after birth, develops continuously thereafter. Devel- opments in speech perception and speech production converge on the child’s production of first words at about twelve months.
Consistent with Jakobson’s theory, acquisition of phonology after the first twelve months represents a linguistic, not merely a motoric, challenge for chil- dren. They gradually extend their phonetic repertoire; many of the fundamental phonetic dimensions Jakobson identified may guide the course of this language acquisition. Although there appear to be general constraints at work on children’s acquisition of phonology, such as early sensitivity to given phonetic dimensions of variation and early limitation to simple (CV-based) word forms, as well as other markedness constraints, there appears to be no universal order of acquisi- tion of sounds (or phonemes) that is revealed across all children independent of the language being acquired.
Development over the first twelve months in acquisition of phonology does not simply reflect maturation, since it differs from language to language. It also does not cohere with a simple “learning theory”; i.e., more experience producing
37Given the possibility for up to seventy or more phonemes in a language, no infants have been tested for the full range of possible contrasts. The boundaries of phonemic categories vary across languages, e.g., along the VOT continuum, as in English vs. French or Spanish. We assume that the infant cannot be born with all boundaries for all contrasts.
proportionately more learning, and thus more knowledge. Instead, during the first year, we see a gradual elimination of response to excess distinctions, resembling a narrowing or “fine tuning” to those which characterize the target language.
The gradual elimination of children’s responses to certain sound distinctions is not due to general decline in perceptual abilities. (a) Infants maintain a sensitivity to sound distinctions where phonemic contrasts based on this distinction exist in the native language. (b) Adults can discriminate non-native sound distinctions when a more sensitive procedure is used and can train to discriminate nearly any non-native contrast (Pisoni, Lively and Logan 1994). (c) Adults can discriminate acoustic cues differentiating non-native contrasts even without training (Werker and Pegg 1992). (d) Some non-native contrasts remain more accessible in adult- hood, e.g., certain Zulu clicks (which “are not at all assimilable to English,”
Werker 1994, 108; Best, McRoberts and Sithole 1988). The facts reviewed above suggest that development involves neither simpleaddition, norloss, but the grad- ualorganizationof a specific phonological system (Werker and Pegg 1992, 297).
The construction of this grammatical system determines how speech input is per- ceived. It begins to do so before the infant speaks a first word (Werker 1994 and Best 1995).
After the first year, children master language-specific word and phrase struc- tures, integrate segmental and suprasegmental units and levels of representa- tion, coordinate the “notes” and create the “score” of their language’s phono- logical system. Constraints are continually modulated by the specific language being acquired. Development involves an increase in language-specific linguistic computation.
8.4.1 Toward an explanation
Because early phonological competencies do not depend on experi- ence of a specific language, they suggest an innate component as their source.38 Because children demonstrate these very early, before lexical learning or meaning or linguistic communication are developed, they appear modular. Do these results reflect an innate “Language Faculty” (e.g., Aslin, Pisoni and Jusczyk 1983, 642)?
Categorical perception characterizes other cognitive areas39 and non-human species (e.g., chinchillas, crickets), and is thus not specific to the Language Faculty.40 However, biological programming may provide a general (cross- species) auditory/acoustic structure which is co-opted by the Language Faculty.
Since non-human species do not develop language, it must be that this audi- tory/acoustic structure is differentially “connected” for the human species to
38It is not clear how a model could be developed which allowed the opposite of the empirical facts:
how could one learn that speech perception should be categorical?
39E.g., perception of color and music (Harnad 1987).
40These cross-species behaviors require thousands of training trials, differing from the human infant who demonstrates sensitivity to the distinctions within the first few minutes of testing (e.g., Jusczyk 1997, 57f.). Some infant abilities appear not to generalize across species, e.g., Kuhl 1987b.