Robin van Rijthoven

34 Chapter 2 verbal working memory may constraint the storage of verbal content when excessive demands are being made, as is the case in word decoding (Swanson et al., 1996). In the course of reading development, word decoding becomes faster, and gradually, most words are recognizedmore or less instantly (Bishop & Snowling, 2004; Nation & Snowling, 2004). Becoming a proficient reader requires having high-quality lexical representations as claimed by the lexical quality hypothesis (Perfetti, 2007). These representations develop by multiple exposures to words that consist of orthographic, phonological, and semantic features (Perfetti & Hart, 2002). For childrenwith dyslexia, however, the acquisition of word decoding is problematic as a consequence of inadequate phonological skills. Already at preliterate age, children at risk for dyslexia have found to be behind in speech decoding (Richardson et al., 2010), phonological awareness, rapid naming, and verbal working memory (Puolakanaho et al., 2007). Their phonological deficit may cause problems in manipulating speech sounds that may hamper the grasping of the alphabetic principle. Moreover, childrenwithdyslexiamay stay behind inphonological recodingof writtenword representations because their phonological lexicon can be considered underspecified (Elbro, 1996; Ramus, 2001). An important question is how a strong capability in semantic abilities may compensate dyslexic children in reading words and pseudowords. Semantic abilities can, according to the lexical quality hypothesis, be defined as a fuller range of meaning dimensions to discriminate among words in the same semantic field (Perfetti, 2007). Not only vocabulary or the broadness of vocabulary but also the depth of the semantic representations thus may be of importance. The depth of semantic representations is defined as the quality of the meaning network surrounding a word (Nagy & Herman, 1987). Most studies only took the broadness of the semantic lexicon into account and not the depth of the semantic representations (Perfetti & Hart, 2002). Interestingly, the semantic representations of children with dyslexia are quite similar to typically developing children (Nation & Snowling, 1998; Swan & Goswami, 1997), which may provide them with the possibility to use their semantic knowledge as a compensatory mechanism. Based on the lexical quality hypothesis (Perfetti & Hart, 2002), a direct effect can be expected of semantic abilities on word reading because a better semantic quality of lexical representations may facilitate word identification. And based on the lexical restructuring hypotheses (see Walley et al., 2003), an indirect effect can be expected of semantic abilities on both word and pseudoword reading mediated by phonology. According to this lexical restructuring hypothesis, the development of preliterate phonological abilities in children with dyslexia can be fostered by a strong lexical development. As the numbers of words and their semantic relations increase, a