PROJECT SUMMARY/ABSTRACT It is estimated that approximately 3-10% of children experience significant and persistent word reading difficulties (Fletcher, 2009). Despite decades of research devoted to reading, there are still many unknowns about the underlying processes involved in word reading (WR) development in children, and more specifically the assemblage of factors that lead to significant word reading failure (i.e., dyslexia). While there is broad consensus that phonemic awareness (PA) and phonemic decoding (PD) skills are important underlying factors (particularly in opaque alphabetic orthographies such as English) that support early WR skill and major determinants of early failure, there is also an evolving realization that broader factors both within and outside the phonological language domain are associated with WR failure. Thus, a deeper understanding of these broader phonological factors/skills associated with word reading development is critical for advancing developmental WR theory and the practical search for new predictors of early WR development that can help to improve on current inaccuracies in the early identification and treatment of individuals who are at risk for word reading difficulty/dyslexia. Recent studies in older readers (grades 2-5) suggest that development of word reading skill in English is heavily dependent on a child’s ability to go from a decoded form of a word (derived during PD) to the stored phonological representation, a phonologically based process we refer to as “phonological clean-up” (PC-U) skill and operationalize with the “Set for Variability” mispronunciation task. Currently, it is unknown whether PC-U skill is a precursor to skilled word reading or a consequence of exposure to text and instruction. This skill has not been assessed in pre-readers nor has the longitudinal stability of its relationship with WR been assessed. The purpose of this proposal is to examine the role of PC-U in supporting early WR development using a longitudinal design in kindergarten-1st grade measuring each skill at the beginning and end of each grade (i.e., 4 time points). Two specific aims are proposed. Aim 1 will explore the underlying mechanisms involved in the relation between PC-U and WR skill. Using advanced statistical techniques we will explore the co- developmental pattern between PC-U and WR examining whether causal links may be present in which level of skill in one variable impacts growth in the other. We will further explore whether development is linked at the word level such that the time a child learns to read a word is associated with PC-U performance on that word. Aim 2 will explore the utility of PC-U as an identifier of risk for early WR difficulties. We will explore whether PC- U performance at the fall of kindergarten contributes to the prediction of word reading at the end of 1st grade after controlling for other kindergarten predictors known to predict word reading. Likewise, the importance of PC- U...