Director, CHILDES - Child Language Data Exchange System , Department of Psychology
BioAmong the many puzzles that language presents to the developmental psychologist, perhaps the most fascinating is the relative ease with which a toddler picks up a first language. Although infants know nothing of the rules of grammar and have only a fragmentary understanding of the physical and social world, they are able to master the core structures of language by the age of three. The ease with which children master their first language contrasts with the more painful and incomplete process of learning a second language in adulthood.
My approach to this problem views language acquisition as an emergent process. Eschewing the traditional opposition betwee nativism and empiricism, I believe that we can better understand language learning as a process grounded on competitive Darwinian processes that operate across a variety of time scales, including a phylogenetic scale, an ontogenetic scale, and a synchronic processing scale.
On the synchronic time scale of online language processing, I view utterances as providing cues that adjudicate the competition between alternative interpretations. Beginning in 1978, Elizabeth Bates and I worked with over 20 colleagues studying processing in 18 different languages to elaborate what we call the Competition Model. The Competition Model views language processing as a series of competitions between lexical items, phonological forms, and syntactic patterns. Competition Model studies have shown that learning of language forms is based on the accurate recording of many exposures to words and patterns in different contexts. If a pattern is reliably present in the adult input, the child picks it up quickly. Rare and unreliable patterns are learned late and are relatively weaker even in adults.
More recently, I have attempted to relate the communicative functions postulated by the Competition Model to the process of perspective-taking. This process allows the human mind to construct an ongoing cognitive simulation based on linguistic abstractions grounded on perceptual realities. The perspective-taking approach views the forms of grammar as emerging from repeated acts of perspective-taking and perspective-switching. Grammatical devices such as pronouns, case, voice, and attachment can all be seen as ways of expressing shifts in a basically ego-centered perspective. One major goal in this new line of research is to better understand the brain mechanisms underlying perspective-shifting.
On the ontogenetic time scale, we can examine language emergence in at least two ways. One methodology uses neural network models to simulate the acquisition of detailed grammatical structures. Beginning in 1989, I have worked on building conectionist models for the acquisition of morphology, syntax, and lexicon in English, German, and Hungarian. More recently, I have examined the ontogenetic emergence of language from a more biological viewpoint, using data on language processing from child with early focal lesions. The results of studies of these children using reaction-time methodologies and standardized tests indicate that, although they have completely normal functional use of language, detailed aspects of processing are slower in some cases. Using functional magnetic resonance imaging technology, we have pinpointing areas of activation involved in specific linguistic tasks. These results have allowed us to evaluate a series of hypotheses regarding sensitive periods for the emergence of language in the brain.
Models of language learning need to account not only for the acquisition of a first language by children, but also for the learning of second languages. The connectionist perspective on second language learning emphasizes the role of transfer and interference. Empirical studies in the Competition Model framework have supported these predictions. We still need to construct a clearer view of the ways in which declines in brain plasticity lead to a loss in language learning ability over time. However, for adults who are able to activated underlying compensatory processes such as the phonological loop and motivational supports, language learning is still possible in adulthood.
Finally, on the phylogenetic time scale, researchers have begun to examine the ways in which language has emerged through competitive Darwinian processes. My work on perspective-taking, competition, and brain mechanisms suggests that the most likely account of the origin of language is one grounded on social mechanisms. In this sense, the elaboration of an emergent account of perspective-taking suggests a Vygotskyan approach to language evolution.