Reading-related skills of youth with intellectual disability (ID) were compared with those of typically developing (TD) children of similar verbal ability level. The group with ID scored lower than the TD group on word recognition and phonological decoding, but similarly on orthographic processing and rapid automatized naming (RAN). Further, phonological decoding significantly mediated the relation between group membership and word recognition, whereas neither orthographic processing nor RAN did so. The group with ID also underperformed the TD group on phonological awareness and phonological memory, both of which significantly mediated the relation between group membership and phonological decoding. These data suggest that poor word recognition in youth with ID may be due largely to poor phonological decoding, which in turn may be due largely to poor phonological awareness and poor phonological memory. More focus on phonological skills in the classroom may help students with ID to develop better word recognition skills.
Individuals with intellectual disabilities (ID) often struggle with learning to read. In a recent large-scale survey, reading difficulties were named the most common secondary condition of ID, with 67% of the sample reporting reading as a secondary problem area (Koritsas & Iacono, 2011). Interestingly, researchers commonly define secondary conditions as those that are preventable ( Koritsas and Iacono, 2011 and Turk, 2006). This implies that, given sufficient knowledge about reading skills and implementation of appropriate training programs, reading difficulties should be somewhat preventable for those with ID. However, until recently, literacy education for students with ID has been largely overlooked by researchers and educators alike ( Katims, 2000). As we now know that many children with ID can learn to read but are still struggling, researchers must explore how they learn to read. This is a necessary step toward designing effective interventions and reading training programs for students with ID. This can be accomplished by first identifying patterns of strength and weakness in reading skill development.
The purpose of the present study is to identify both strengths and weaknesses in reading skills of students with ID. To do this, we look to the skills that are important in learning to read in the typically developing (TD) population. The well-known Simple View of Reading proposed by Gough and Tunmer (1986) suggests that there are two main components of reading: word recognition (identifying words in print) and language comprehension (extracting meaning from the words). Whereas both components are important, the relative significance of each changes across development (Gough et al., 1996 and Vellutino et al., 2007). The focus of early readers is often word recognition. Later in reading development, the focus usually shifts toward comprehension. Because the sample in our study consists of students who are struggling to read at the beginning stages, our focus is on word-level reading rather than comprehension.
In the literature on TD readers, researchers have identified three primary skills that are used in word recognition: phonological decoding (Kirby et al., 2003, Parrila et al., 2004 and Wagner et al., 1997), orthographic processing (Barker et al., 1992, Cunningham et al., 2001 and Cunningham and Stanovich, 1990), and rapid automatized naming (RAN; Kirby et al., 2003, Parrila et al., 2004 and Wolf and Bowers, 1999). These three skills, described in detail below, are unique contributors to word recognition in TD children but have not been fully examined in participants with ID.
