Robin van Rijthoven

94 Chapter 4 In line with the first hypothesis, children with dyslexia made more phonological, morphological, and orthographic errors compared to typically developing children. These results confirm previous research (Bourassa & Treiman, 2003; Bourassa et al., 2006; Cassar et al., 2005). In accordance with our second hypothesis, we found that orthographic spelling is more difficult for all spellers. This finding confirmed that more specific knowledge of rules and orthographicpatterns isnecessary for orthographic spelling (seeAllen, 1992). Bothchildren with dyslexia and typically developing children made proportionally most morphological errors, followed by orthographic and phonological errors. In addition, when comparing the relative differences between children with dyslexia and typically developing children, results showed that children with dyslexia differed most from typically developing children on phonological errors compared to morphological and orthographic errors. The fact that children with dyslexia struggle more than typically developing children with phonological errors follows from their phonological deficit, which prevents children with dyslexia from building strong bi-directional connections between phonological and orthographic representations (Cassar et al., 2005; Snowling, 1998). In compliance with our third hypothesis, we found that for children with dyslexia morphological errors were negatively associated with verbal working memory and phonological, morphological, and orthographic errorswere negatively associatedwith their level of semantic abilities. The impact of verbal working memory on morphological errors is also highlighted in the Morphological Pathways Framework, suggesting that additional workingmemory isneeded inthesecases (Levesqueetal., 2021). The importanceof semantic abilities for both phonological and orthographic spelling is in line with the lexical quality hypothesis (Perfetti, 2007); semantic abilities could be seen as a compensatory factor for both phonological and orthographic spelling. We showed that semantic abilities is not only important for reading (Nation & Snowling, 2004) but for phonological and orthographic spelling as well. This is in line with the connectionist model of Plaut and colleagues (1996) in which literacy development was described in terms of a division of labour between interacting phonological and semantic pathways. Variation in both phonological and semantic processing could be related to individual differences in literacy development, whereas children with dyslexia rely on contributions from the semantic pathway because of their poorly developed phonological pathway (Nation & Snowling, 1998; Snowling, 2000). However, longitudinal studies are necessary to understand the complex interplay between phonological and semantic abilities as been indicated by Laing and Hulme (1999). With regard to our fourth hypothesis, we found a decline in the error percentages in all three error categories after a phonics through spelling intervention. The change per session (decline in error percentages) was highest for morphological errors, followed