This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The ability to turn thoughts into words is central to communication and learning. The earliest form of this uniquely human skill is object name production. Children begin using words to name familiar objects around their first birthday. Over the next several months new words are slowly added to their productive repertoire. Many researchers have noted that towards the end of the second year, there is a striking increase in the rate of productive vocabulary growth. As children develop increasingly larger and more complex language systems, a major challenge is to locate information quickly and easily. The focus of this research is on how the lexical processing system develops in response to this challenge. Previous investigations support the idea that the lexicon is a complex and dynamic entity. In children, especially, the emergent lexicon is continuously subject to change and reorganization as new words are added and lexical neighborhoods (groups of related words) are formed. More words in the lexicon increase the opportunity for competition during retrieval. The need to retrieve a growing number of lexical items quickly and accurately thus may serve as an impetus for system-wide changes in how words are processed early in the course of word acquisition and production. In the current research, the critical question is whether there is a point in development when lexical processing is no longer guided by the properties of individual words alone, but rather by the ensemble of words belonging to a single system. Such a shift would suggest an increase in automaticity. Automatic processes are typically fast and require little attention and effort. The benefit of automaticity would be to free up cognitive resources for other cognitive and linguistic tasks. A number of key components are implicated in the simple act of naming: processing the visual or perceptual attributes of objects, matching this information to memory, linking semantic representations of the objects to their phonological forms, and formulating and executing words for production. Early in development, children seem to invest considerable effort in these processes. The primary objective of the present research is to investigate the mechanisms associated with word retrieval and the developmental changes that underlie improvements in naming. The principal technique used for investigating these processes is children's failures of retrieval, that is, the errors they produce when attempting to name familiar objects. Such errors provide a unique window onto the structure and operations of the lexicon as they change with increased vocabulary growth. The investigation will include both typically developing children and children with specific language impairment who experience difficulties with naming. This clinical population is characterized as having normal comprehension skills and nonverbal intelligence, but problems with retrieving words from lexical memory.
This research will make an important contribution in three major respects. First, the project will provide new empirical findings and theoretical insights into how children develop the skills needed to become mature speakers of language. Second, the findings will have relevance for existing models of adult language production and help to bridge knowledge of the word retrieval operations in novice and experienced word learners. Third, the research will contribute new understanding of the critical differences between normal and language impaired children and may provide practical benefits for understanding the etiology of those identified with word finding problems. In particular, the behavioral data obtained from this research should enhance the adoption of best practices in the assessment and early intervention of children at risk for lexical processing disorders.
