Several studies have shown that different components of reading (word decoding, spelling, and reading comprehension) demand different skills and are predicted by different compositions of cognitive and linguistic child factors (e.g., Papadimitriou & Vlachos, 2014; Perfetti & Stafura, 2014). In the current dissertation, the variation in a wide scope of factors was measured, resulting in a child profile of individual performances on phonological, orthographical, semantic, and memory skills. This child profile was related to the longitudinal development of three components of learning to read. Findings were in line with the expectation that code-based skills of phonological awareness and grapheme-to-phoneme knowledge would be especially predictive for later word decoding development and for spelling (Chapter 2 and 3), whereas the meaning-based skill involved in the vocabulary task would be a
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prominent predictor for later reading comprehension (Chapter 5). As expected it was also found that lexical retrieval skills as measured in rapid naming were particularly relevant in predicting word decoding efficiency, and that short term memory was directly predictive for the developmental domains of word decoding and reading comprehension.
An important finding with regard to the second research question of the current dissertation was the omnipresent influence of phonological awareness in the prediction of learning to read. Apart from word decoding development, also spelling in Grade 1 and 2 (Chapter 3) and reading comprehension in Grade 2 and 3 (Chapter 5) were directly predicted by phonological awareness skills. One explanation for the high predicting value of phonological awareness skills in all domains of learning to read, might be the prominent role of phonological information in the core component skill of reading, namely word decoding. This prominent role of phonology in word decoding has been theoretically described in the Lexical Quality theory (Perfetti, 2007) and the Triangle model of reading (Harm & Seidenberg, 2004; Plaut et al., 1996; Seidenberg & McClelland, 1989) and the evident position of word reading and related skills in the development of reading comprehension, has been emphasized in the Reading System Framework of Perfetti and Stafura (2014). This current population wide study of early reading development in the transparent orthography of Dutch empirically evidenced that phonological awareness skills contribute to the direct prediction of all core elements of learning to read.
In addition to phonological awareness skills, rapid naming was found to be highly predictive for the development of word decoding efficiency. That was shown already during the incremental building of the alphabetic principle (Chapter 2 and 4), and with ongoing (direct) contributions later during Grade 1 and Grade 2 (Chapter 3 and 5). This suggests that rapid naming remains longitudinally contributive to word decoding development. In contrast, no direct contribution of rapid naming on the prediction of spelling was found (Chapter 3), nor on reading comprehension (Chapter 5). It has been argued that rapid naming skill reflects orthographic processing skills like lexical retrieval (Moll et al., 2014). Although some orthographic processing skills were assumed in spelling activities, automatization of lexical retrieval turned out to be less important for the prediction of spelling development. Children learning to spell in Dutch orthography profit more from well-developed phonological awareness skills than from rapid naming skills. Previous literature in other orthographies (Chinese, Finnish, and English) also found rapid naming to be prominent in the prediction of
word decoding but not in the prediction of spelling (Georgiou, Aro, Liao, & Parrila, 2016; Verhagen et al., 2010; but see Lervag & Hulme, 2010). It comes along (and should be noted) that, apart from reflecting orthographic processing skills, rapid naming skills are also a reflection of speed of cognitive processing in general. During spelling and reading comprehension measurements, no speed element was measured in contrast to measurements of word decoding efficiency (e.g., Kirby, Desrochers, Roth, & Lai, 2008; Lervåg & Hulme, 2010).
Concerning the other cognitive and linguistic factors studied in the current dissertation, results indicated that vocabulary knowledge was a particularly strong predictor of reading comprehension (Chapter 5). That is in line with theories explaining the crucial role of lexical quality in reading comprehension (Perfetti, 2007). Furthermore, current research indicated the predicting role of verbal and visual short term memory in both word decoding and reading comprehension development (Chapter 2 and 5). The predicting role of visual memory on reading performances has been evidenced before (Van den Boer et al., 2013; Bosse and Valdois, 2009), and was now also indicated during the first months of reading instruction. The fact that direct contributions of verbal short term memory skills come in only later during developmental steps for both word decoding (after three monthly measurements; Chapter 2) and reading comprehension (after the second Grade 2-measurement six months later; Chapter 5), might indicate the specific role for (verbal) memory skills as soon as tasks become more demanding in terms of either more complex word structures, or more complex text structures.
Concerning the longitudinal prediction of word decoding development by cognitive and linguistic factors, it is pronounced that results in Chapter 3, 4, and 5 expand findings of Chapter 2 in showing that the kindergarten characteristics remained predictive for the development of word decoding efficiency beyond the phase of mastering the alphabetic principle. That means that the same cognitive and linguistic kindergarten skills impact word decoding over at least the first year of reading instruction. This can be explained by the stable nature of the word decoding skill in learning to read in Dutch. In Dutch, word decoding development is a matter of growing efficiency (accuracy per time element) from the very beginning of formal reading instruction (Chapter 2). The current dissertation showed ongoing development of word decoding efficiency in Grade 1 and 2 (Chapter 3, 4 and 5).
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The findings of the current longitudinal study highlight the important influence of phonological, orthographic, semantic, and memory skills in children’s early reading development. The precursor skills differentially relate to the components of reading development.