The Role of Lexical and Phonological Complexity in Early Vocabulary Growth

Matthew Carlson

From birth to school entry children’s lay a foundation of language development that will have important effects on their further development after school entry. Understanding variability between children at these crucial early stages is vital to understanding later development as well as to designing effective instruction. This study focuses on the development of phonological knowledge in the early lexicon, linking phonological structure to the particular contents of the lexicon as well as to vocabulary growth.Evidence suggests that while children favor words with frequent sound patterns, they may have difficulty acquiring highly similar words (e.g. cat/cap). The present research builds on these earlier experimental findings by tracking vocabulary growth in 1- to 5-year-olds using naturalistic speech samples. However, measures of phonological form have traditionally been based on sequences of individual phonemes, and similar words have been defined as differing in a single phoneme, such that all words differing in 2 or more phonemes as equally distant. These operational definitions are limited because they may not accurately reflect the structure of the child lexicon. Therefore, this project seeks to develop more sophisticated measures of phonological form and word similarity by incorporating higher-level phonological structures (e.g. the syllable) and by utilizing more continuous measures of similarity between words.By utilizing these innovations to analyze a large, longitudinal database, this project opens significant possibilities for understanding differences between children in language development and, importantly, subsequent success in reading. For instance, some children may have a higher tolerance for similarity or complexity in their vocabularies, which in turn may influence their success in learning to read.

About Matthew Carlson

Matthew Carlson earned his AB from Dartmouth College in 1996 and his K-12 foreign language certification in 1997. After four years of teaching Spanish grades 8-12, inspired and intrigued by this interaction with second language learners, he decided to pursue graduate work studying second language acquisition, completing MAs in Spanish (2003) and German (2005) before being awarded his Ph.D. in Spanish Linguistics from the Pennsylvania State University in 2007). In his dissertation, directed by Chip Gerfen, Dr. Carlson investigated how subtle subregularities in the Spanish lexicon are taken up by individuals learning Spanish after the onset of puberty, and whether learners develop a fine-grained sensitivity to these patterns similar to that observed in native speakers. Currently, he is a postdoc in Developmental Psychology at the University of Chicago, working with Susan Goldin-Meadow, Susan Levine, and Howard Nusbaum. In Chicago he has continued his diverse training through work on preschool language development as well as the use of gesture by bilinguals. Dr. Carlson’s work builds on this vitally cross-disciplinary training, blending techniques and insights from linguistics, cognitive and developmental psychology, and education. He incorporates sophisticated statistical analysis of grammatical structure and sensitive measures of speakers’ knowledge and use of language to understanding language learning as a lifelong developmental process. This allows for a nuanced understanding of how language experience shapes people’s implicit knowledge of their language(s), the cognitive and social mechanisms through which this takes place, and how changes in language use (e.g. the onset of literacy or the learning of a second language) affect language development. Within this global perspective, Dr. Carlson’s research has focused on emergent phonological and morphological grammar and on bilingualism and language acquisition to learn how language knowledge and use evolve through periods of both stability and change, from birth through adulthood, for each individual