Children with language impairment (LI) comprise nearly 20% of the population receiving special education services (Tomblin et al., 1997) and are six times more likely to have a reading impairment than their peers with typical language development (Stoeckel et al., 2013). Whereas most children with LI have poor reading comprehension (Catts et al., 2002), fewer than half have poor word-reading abilities, commensurate with dyslexia (Catts, Adlof, Hogan, & Weismer, 2005). In two large-scale studies that examined longitudinal reading outcomes in children with LI, factors could not be identified that reliably distinguished kindergarten children with LI who would go on to have good word reading abilities versus those who would go on to have dyslexia in 2nd grade and beyond (Catts et al., 2005; Bishop et al., 2009). The inability to distinguish future word-reading outcomes for young children with LI creates a critical barrier to efficacious treatment and prohibits optimal use of limited therapy time to address individual children's needs. Contemporary models of typical reading development center on a reciprocal relation between orthographic processing (letters and letter patterns) and phonological processing (sounds and sound patterns). In these models, early phonological processing underpins acquisition of the alphabetic principle (that letters represent sounds) and subsequent word reading, and in turn, orthographic knowledge impacts phonological processing (Share, 1995; Ziegler & Ferrand, 1998). Accordingly, orthographic and phonological processing are correlated in emerging typical readers and continue to develop in tandem with increasing word reading abilities (Hogan, Catts, & Little, 2005; Wagner et al., 1997). However, contemporary models cannot explain why more than half of children with LI develop good word reading skills despite early phonological processing weakness (Catts, Adlof, Hogan, & Weismer, 2005). Despite its significance to typical reading development, orthographic processing has largely been ignored in studies of children with LI. Our compelling pilot data are the foundation for our hypotheses that: a) initially weak phonological processing is compensated for by orthographic strengths in children with LI, and b) these early orthographic strengths will predict who among young children with LI will go onto have good word reading versus those who will go on to have dyslexia.
Our specific aims are: 1) to determine the impact of exposure to orthography on the acquisition of new orthographic and phonological forms during word learning and how this changes over time in children with LI and their typically developing peers; 2) to characterize profiles of orthographic and phonological processing in children with LI and their typically developing peers from kindergarten to 2nd grade; and 3) to determine predictors of development in orthographic processing, phonological processing, and word reading in children with LI and their typically developing peers.
Our aims fill a theoretical gap in which orthographic processing has been overlooked in reading and word learning studies involving children with LI, and they address methodological limitations that have negated conclusive findings on the reciprocity between phonological and orthographic processing. Our rigorous approach combines longitudinal research with carefully controlled experimental work. The innovation of this project includes our use of a novel, dynamic word learning paradigm, which captures phonological and orthographic knowledge and learning in a single task. Our findings will have broad clinical and theoretical impact by contributing to our long-term goals a) to create more precise tools for early identification of reading impairments in children with LI; b) to reveal theory-based mechanisms for the interrelated development of orthographic processing, phonological processing, and word reading; and c) to quantify orthographic and phonological learning profiles to inform individualized reading interventions.
This longitudinal project aims to contribute to a better understanding of the mechanisms by which children with language impairment learn words and develop language and literacy skills during a critical early period of formal reading instruction. This project is relevant to the NIDCD's mission to improve the lives of individuals with communication disorders because findings from the proposed studies are expected to be informative for refinement of prognosis, assessment, and treatment methods for this population. This project is also relevant to the broader field of public health because of the importance of language and literacy skills to quality of life outcomes.