The third research question of the present dissertation was how children’s age of onset is related to their responsiveness to intervention. Children’s initial reading and spelling abilities were, together with their cognitive abilities, added as predictors of their responsiveness to intervention after the declarative phase of the intervention in Chapter 3 and to the prediction of the sustained intervention in Chapters 4 and 5. In addition to the initial abilities and cognitive precursors, the growth during the intervention as well as the precursors class repeat, group (being dyslexic or not) and grade (early versus late) were
added in the prediction of responsiveness to intervention in Chapter 5. Predictors of responsiveness to the declarative phase of the intervention
As the declarative approach of the clinical phonics intervention mainly focused on grapheme-phoneme learning in order to read and spell monosyllabic words, precursors in Chapter 3 were related to the dependent variables word and pseudoword reading and spelling outcomes and to letter naming as well. In the literature so far, letter knowledge is frequently included as one of the predictors (see for example Foulin, 2005), and less as a dependent variable to which precursors are related. To begin with the prediction of letter knowledge, results in Chapter 3 revealed that the speed of naming grapheme- phoneme correspondences during the declarative phase of the intervention can directly be predicted by children’s rapid automatized naming abilities, their verbal working memory skills and their phonological awareness. These cognitive characteristics underlying dyslexia (Berninger, Raskind, Richards, Abbott, & Stock, 2008), thus impede children’s responsiveness to intervention. In the prediction of the other dependent variables, the cognitive precursors showed no direct effect on the prediction of intervention outcomes on real- and pseudoword reading and spelling during the declarative intervention approach. Thus, although individual differences in precursor measures play a minimal role in the prediction of children’s responsiveness to reading and spelling outcomes, which is in line with previous findings (Tijms, 2011), responsiveness to intervention on letter knowledge largely depends on several cognitive characteristics in children with dyslexia. The predictive role of rapid automatized naming is not surprising, as the ability to speed up the naming of grapheme-phoneme correspondences is closely related to serial naming abilities. The predictive role of phoneme deletion is neither surprising as it assumes the ability to segment elements of words. A critical note, however, should be made about the role of verbal working memory in predicting children’s responsiveness to intervention. Verbal working memory was still relevant in predicting responsiveness to intervention. Symbolic scaffolds did thus not reduce the overload in children’s memory to such an extent that verbal working memory differences did not play a role anymore.
Thus, although the role of cognitive aspects is minimal in predicting responsiveness to intervention on reading and spelling abilities, in the prediction of children’s responsiveness to intervention on letter knowledge cognitive aspects are certainly important. However, it remains unclear to what extent the incomplete letter knowledge is due to dyslexia or to the educational system. If children’s delay in letter knowledge is not resolved using the declarative aspects of the intervention, the approach should be adjusted, by, for example, considering the role of underlying cognitive precursors.
Predictors of responsiveness to the sustained phase of the intervention
Where the prediction of responsiveness to declarative phase of the intervention is related to initial abilities in reading and spelling and less to cognitive predictors, the studies described in Chapter 4 and 5 showed the important role of underlying cognitive factors to the prediction of children’s responsiveness to intervention during the second, sustained phase of the intervention.
With respect to efficiency, results reveal that besides initial abilities responsiveness to the clinical intervention can best be predicted by rapid automatized naming abilities. The present dissertation replicates findings of previous studies in which the predictive role of rapid automatized naming abilities has been proved as precursor of intervention outcomes (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001; Scheltinga, van der Leij, & Struiksma, 2010; Zoccolotti, De Luca, Marinelli, & Spinelli, 2014). Where rapid automatized naming abilities of children with dyslexia were important in predicting efficiency outcomes, phonemic awareness directly predicted accuracy outcomes. This is in line with a study by Otaiba and Fuchs (2002), although it should be noticed that the predictive role of phonological awareness in Chapter 4 is limited to pseudoword reading and not for the reading of real words. Where letter knowledge was only a dependent variable during the first phase of the intervention, in Chapter 4 and 5, it was added as a precursor of responsiveness to the sustained intervention. Surprisingly, neither in reading, nor in spelling, letter knowledge predicts children’s responsiveness to intervention. Nevertheless, the role of precursors on the prediction of responsiveness to the sustained phase of the intervention was limited to initial abilities, rapid automatized naming and phonological awareness. In addition to the prediction of responsiveness to the sustained intervention in Chapter 4 which involved second graders, in Chapter 5 it was further examined to what extent the age of onset of dyslexia adds to the prediction of intervention outcomes. ‘Grade’ (second graders with dyslexia versus third graders with dyslexia) was added as precursor in the prediction of responsiveness to intervention. Based on the results in Chapter 5 there is no substantiation that early intervention leads to more responsiveness to intervention. The prediction of responsiveness to intervention is limited to initial reading abilities and their rapid automatized naming.
To conclude, in the prediction of children’s responsiveness to the sustained intervention initial reading abilities and cognitive predictors play an important role. The age of onset does not add to the prediction of children’s responsiveness to intervention. Early intervention, which is recommended by many studies (see for example Singleton, 2009), cannot be claimed based on the findings of Chapter 5.