Starting Over: International Adoption as a Natural Experiment in Language Acquisition

Starting Over: International Adoption as a Natural Experiment in Language Acquisition Jesse Snedeker (snedeker@wjh.harvard.edu) Joy Geren (geren@wjh.harvard.edu) Department of Psychology, 33 Kirkland St. Cambridge, MA 02138 USA Abstract Language development is characterized by predictable shifts in the words that children learn and the complexity of their utterances. Because language acquisition typically occurs simultaneously with cognitive development and maturation, it is difficult to determine the causes of these shifts. We explored how acquisition precedes in the absence of possible cognitive or maturational roadblocks, by examining the acquisition of English in internationally-adopted preschoolers. Like infants, and unlike other L2 learners, these children acquire a language from child-directed speech in the home, without access to bilingual informants. Parental reports (CDI- 2) and speech samples were collected from 14 preschoolers, 3 to 18 months after they were adopted from China. These children made rapid progress in acquiring English and showed the same developmental patterns as monolingual infants (matched for vocabulary size). Early on, their lexicons were dominated by nouns, their utterances were short, and function morphemes were almost entirely absent. Children at later stages of development had more diverse lexicons and produced longer utterances with more closed-class morphemes. Introduction Language development is marked by a series a qualitative shifts. Infants speak in single-word utterances for several months before beginning to combine words. Young children learn a disproportionate number of nouns before acquiring a balanced complement of verbs, adjectives and prepositions. Young English speakers typically omit function morphemes from their early word combinations, and then gradually begin to add them in. A central question in language acquisition is what causes children to move through these phases (Lenneberg, 1967, Bloom, 1973, Gleitman & Newport, 1995, Ganger, Pinker, Chawla & Baker, 2004). Are the early stages reflections of cognitive immaturity or do they represent necessary steps in decoding the target language? Is the emergence of new linguistic abilities driven by maturation or by the child’s growing knowledge of the language? These questions are difficult to answer because language acquisition is confounded with cognitive development and maturation in typically developing children. However much of what we know about language development comes from studies of atypical populations. Research on aphasics suggested there might be a critical period for language acquisition (Lenneberg, 1967), a hypothesis confirmed by studying adults deprived of linguistic experience in childhood (Newport, 1990). Research on blind children (Landau & Gleitman, 1985), linguistic isolates (Goldin-Meadow & Feldman, 1977), and children with limited language models (Singleton & Newport, 2004) has been central in demonstrating the resilience of children’s linguistic abilities. These natural experiments allow us to explore the effects of variables that are impossible or unethical to manipulate. International adoption provides the opportunity for just such a natural experiment. Over 20,000 internationally- adopted children enter the U.S. each year. While most are infants or toddlers, thousands of older children are also adopted. Typically these children rapidly lose their birth language (Glennen & Masters, 2002). By adulthood, they fail to distinguish speech in their birth language from an unknown language and show no cortical activations that distinguish them either (Pallier et al., 2003). Most of these children are adopted well within the sensitive period for language acquisition (Newport, 1990) and become fluent speakers of their new language (Pallier, et al., 2003). But we know almost nothing about how they get there. Recent studies show that internationally-adopted infants make rapid progress in acquiring English (Glennen & Masters, 2002). But there is no existing data on older adoptees. The learning problem faced by these children is broadly similar to that of infants learning their first language: they are exposed to child-directed speech in the context of daily routines; they must learn the new language to communicate with their families; they have little access to text or bilingual informants; and they lack many of the metalinguistic abilities available to older children and adults (Gombert, 1992). However, these children are more cognitively and physically mature than their infant counterparts and have already started to learn one language. The current study compares language acquisition in internationally-adopted preschoolers and monolingual infants. Our goal is to explore the role that cognitive development and maturation play in shaping the course of first-language acquisition by examining how acquisition proceeds when these road blocks have been removed. By doing this we hope to tease apart two very broad kinds of explanation for systematic changes during language acquisition: 1) Maturational-Cognitive Hypotheses: Theories of this kind attribute the order of acquisition or the emergence of new abilities to changes in the learner which are independent of the child’s experience with