Spoken word recognition lies at the root of language comprehension and acquisition. Recognition of known words (numbering in the tens of thousands for adults) is prerequisite for retrieval and storage of semantic, syntactic, and pragmatic information associated with those words. Typically, such recognition is fast, accurate, robust, and effortless. Yet the perceptual computations required are highly complex, as anyone listening to speakers conversing in an unfamiliar language begins to discern: what one hears is a babble lacking readily identifiable words. Nevertheless, within the first year of life, infants must develop the skills needed for spoken word recognition. Such skills are prerequisite to further acquisition of language, for if a language learner cannot break input utterances into their constituent words, it will be impossible to learn how these words fit together or what individual words mean. Research proposed in this application focuses on elucidating precursors to, and predictions from, development of spoken word recognition. This project seeks to explore causal pathways from early cognitive development, basic speech perception skills, and language experience to development of spoken word recognition and early language knowledge, and hence to pre-school language outcomes. A pair of integrative longitudinal studies will measure infants from birth to 24 months on batteries of tests assessing cognitive and linguistic development;language environments will also be measured. A further battery of tests at 36 months will assess pre-school language outcomes. One longitudinal study will enroll full-term infants to establish normative baselines. The second, concurrent study will enroll preterm infants (<28 weeks gestation): language delays and deficits are associated with low birth weight, and preterm infants receive markedly different early input, but it is not known whether the causal structure of language development differs across the two populations. Specific questions to be addressed include: What is the relation between early (segmental and prosodic) discriminative and representational abilities and development of spoken word recognition skills? Are effects of cognitive development on language outcomes in pre-school years mediated by early spoken word recognition skills? How does absolute performance on cognitive and linguistic measures at specific ages in infancy compare to changes in such performance across ages (growth curves) with regard to predicting pre-school language outcomes? How do variations in informational quality and quantity affect early speech processing, development of spoken word recognition, and pre-school language outcomes?
Anyone who has listened to fluent conversation in an unfamiliar language can readily attest that recognizing spoken words is a far from trivial skill, but without this skill it is impossible either to comprehend speech or to master combinatorial or compositional 'higher'levels of language. Language deficits and delays impede intellectual development for hundreds of thousands of individuals. This application incorporates two longitudinal studies that examine the relation between development of spoken word recognition skills and pre-school language outcomes. One explores receptive language development in healthy full-term infants, examining how such development may be determined by both endogenous factors, including cognitive abilities, speech perception skills, and fluctuations in infants'functional hearing, and exogenous factors, such as input quantity. A second, concurrent study explores language development in preterm infants, a population known to be at risk for language delays. The overarching goals of these studies is to elucidate the pathways from early cognitive development, basic speech perception skills, and language experience to development of spoken word recognition and early language knowledge, and hence to pre-school language outcomes, and to examine how these pathways may differ for the two populations to be studied.