146 Chapter 6 readers and spellers and did not lead to proficient reading and spelling after a phonics through spelling intervention. However, in the complex interplay of multiple cognitive factors these two factors give children with dyslexia an additional boost, which may have prevented them from even weaker performances in reading and spelling. Limitations and future perspectives This dissertation showed two possible compensatory sources for children with dyslexia, but some limitations shouldbeacknowledgedat thispoint alongwithrecommendations for future research. First of all, the data used to answer the first research question were cross-sectional. In addition, the participants included in the dissertation showed large variation in age, and, with regard to the reported effect of semantic abilities on reading and spelling errors in chapter 2, 3, and 4, control groups of typically developing peers missed. Causal conclusions should thus be regarded with caution, and larger samples with a more homogeneous age-group of children with dyslexia compared to readingmatched and age-matched control groups are needed to replicate the current findings. As a case in point, Van Viersen and colleagues (2017) studied the role of semantic abilities and family risk for dyslexia in two developmental pathways towards reading comprehension, through word reading and through oral language abilities. They followed children with a risk for dyslexia and controls between 4 and 12 years old and our finding that semantic abilities are at the base of preliteracy skills and thereby word decoding replicates their conclusion. Second, we found that a phonics through spelling intervention is beneficial for both reading and spelling. However, control conditions and data on the effectiveness of elements of the intervention were not part of this dissertation and, therefore, it remains unknown whether the intervention is more successful than others and which elements are particularly effective. In line with Galuschka and colleagues (2014), we found in this dissertation that a phonics intervention is successful, but future research could compare different forms of phonics interventions (including a phonics through spelling intervention). This could focus on the intervention as a whole and different elements of the interventions to gather knowledge about what works best for children with reading and spelling problems. Since the phonics through spelling interventionmost difference from other phonics interventions in the amount of spelling instruction and exercise, it would be interesting to compare the results of the intervention to interventions that included reading solely, spelling solely and both in different proportions. Based on the fact that spelling is more difficult than reading (Bosman & Van Orden, 1997) and the fact that knowledge of spelling transfers to reading and vice versa (Conrad, 2008) we expect that a combined intervention is more effective and that integrating spelling to a bigger extent is the best way to facilitate literacy development.
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