15 General introduction 1 In line with the lexical restructuring hypothesis, converging evidence from neuroimaging studies (e.g., Shaywitz et al., 2005) as well as the triangular framework (Seidenberg & McClelland, 1989) suggest that high-quality semantic representations could be a source of compensation for the weak orthographic and phonological representations in children with dyslexia. However, most studies regarding the role of semantic abilities in reading and spelling were performed among typically developing children, children with reading problems, or children at risk for dyslexia. Research among children with the actual diagnoses of dyslexia is currently missing. Furthermore, the existing research mostly included the broadness of vocabulary (i.e., quantity). However, in contrast to the broadness of the available semantic network, the depth of the semantic representations seems to be a better indicator of the semantic representations that are necessary in order to compensate for weaknesses in the phonological representations. To be more specific, according to the lexical quality hypothesis, semantic abilities can be defined as a fuller range of meaning dimensions to discriminate amongwords in the same semantic field (Perfetti, 2007), which is reflected in the quality of themeaning network surrounding a word (i.e., Nagy & Herman, 1987). In order to find out the compensatory role that semantic abilities can play, the depth of the semantic representations should therefore be included as well. As children with dyslexia could benefit from a well-developed semantic network, the ability to expand the specificity and redundancy of the (phonological) lexicon could be important too. In order to develop such a lexicon, one needs to be able to learn and consolidate verbally presented information in memory, processes that are also known as verbal learning and verbal consolidation (Kibby, 2009). As differences between children with dyslexia and typiccaly developing children were found in verbal learning (e.g., Elbro et al., 2005; Kibby, 2009) and in a single case also in consolidation (e.g. Kibby, 2009; Kramer et al., 2002) this could possibly be a facilitating or constraining factor causing differences in reading and spelling outcomes. Only two studies related verbal learning and consolidation (measured by verbal list learning) to reading and spelling outcomes (Kibby, 2009; Tijms, 2004) and only one study did so for verbal consolidation (Tijms, 2004). However, the debate on the compensatory role of verbal learning and consolidation can best be called inconclusive for several reasons. First, research so far, did not include a typically developing control group, nor did it control for all other important cognitive factors (phonological awareness, rapid automatized naming, verbal working memory and already acquired semantic abilities). Second, differences in conceptualization of verbal learning could have influenced the results because the operationalization of a learning measure should not reflect the result at the end of the learning process (see Tijms, 2004; Kibby, 2009) but should rather focus on the learning process itself. No prior study related this dynamic aspect of verbal learning and consolidation to reading and spelling outcomes, which is important because this shows the learning potential of semantic information that could facilitate phonological representations.
RkJQdWJsaXNoZXIy MTk4NDMw