The effect of oral language, particularly phonological skills, on reading accuracy has been extensively studied as discussed above. In contrast, there has been much less research on the reverse relationship, i.e. the impact of reading accuracy on oral language. This will be discussed in regards to children with Down syndrome later in this chapter, and therefore studies in typical development are relevant.
Ziegler, Muneaux and Grainger (2003) considered the effect of orthography on phonology in the context of the lexical restructuring hypothesis; they argued that as the number of acquired orthographic representations increases, this may also promote segmental phonological representations. This can be related to Perfetti and Hart’s (2002) lexical quality hypothesis, of which the key premise is that a lexical representation is high quality when it has fully specified orthographic, phonological and semantic representations. It is also suggested that reading practice can produce better specified lexical representations and one mechanism by which this occurs could be by promoting the segmental nature of phonological
representations.
A number of studies have taken advantage of an opportunity to avoid the confounds of social or medical factors to study the effect of illiteracy in a Portuguese community. These studies have focused on phonological skills and have found that adults who never learnt to read were poorer on phonological awareness tasks and nonword repetition than those who had learnt to read (Castro-Caldas, Petersson, Reis, Stone-Elander, & Ingvar 1998; Morais, Cary, Alegria, & Bertelson, 1979). Morais et al. (1979) suggested that the explicit awareness and manipulation of phonemes is not a necessary prerequisite for learning to read, but the underlying cognitive ability for this awareness to develop is, and there is a reciprocal relationship between development in reading accuracy and phonological awareness.
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Hulme, Caravolas, Malkova and Brigstocke (2005) outline two versions of the theory that increasing orthographic knowledge promotes phonological awareness. The strong version is that there is an item-specific relationship between acquiring grapheme-phoneme
correspondences and phoneme awareness, i.e. children learn to successfully manipulate phonemes they know the letter for. A second, weaker, account of the relationship is that learning grapheme-phoneme correspondences results in children acquiring the alphabetic principle and the knowledge that spoken words can be segmented into their constituent phonemes. However in this study, children successfully completed phoneme awareness tasks for phonemes they did not know the letter for and some children with no letter-sound knowledge succeeded on phoneme awareness tasks. This contradicts both versions of the theory, particularly the stronger one. Hulme et al. conclude that although there may be a reciprocal relationship between orthographic and phonological relationships, learning to read is not a necessary prerequisite for phoneme awareness to develop.
If learning to read does indeed affect oral language skills, then it may be expected that this would lead to changes in the functional organisation of the brain. To investigate this Castro-Caldas et al. (1998) asked six literate and six illiterate women to perform word and nonword repetition tasks whilst undergoing a PET scan. In addition to finding an effect of literacy on both tasks, there were differences in the areas activated in the brain. For the literate women, there was more activation unique to the nonword repetition task, which the authors suggest represents a neural network that is involved in the processing, organisation and production of new phonological output, i.e. a nonword. The implication is that learning to read promotes explicit phonological processing and the use of this network. The ability to decode words, i.e. break words down into their constituents, is transferred to oral language and whole words are automatically split into their individual phonemes (Frith, 1998; Nation & Hulme, 2011).
The possible effect of reading accuracy on phonological skills in typically developing children has also been examined. Nation and Hulme (2011) examined the longitudinal relationship between reading accuracy and nonword repetition when children were aged 5-6 years and 6-7 years. Concurrently, reading accuracy predicted nonword repetition at the second time point, but not the first. Longitudinally, reading accuracy predicted nonword
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repetition and this was independent of a measure of oral language and the autoregressor. It was argued that learning to read helps create segmental phonological representations and therefore leads to more accurate repetition of nonwords.
Children with specific language impairment (SLI) typically have difficulties with phonological short-term memory and difficulties on nonword repetition tasks are seen as a cognitive marker of SLI (Hulme & Snowling, 2009). Children with SLI often also present with literacy difficulties, therefore Conti-Ramsden and Durkin (2007) examined the longitudinal relationship between these two skills in adolescents with SLI between the ages of 11 and 14 years. There was a reciprocal relationship between reading accuracy and nonword repetition, although this was not significant when the autoregressors were entered. It should be noted that there was little growth in nonword repetition over the course of the study hence it would be difficult for any variable to contribute significantly to nonword repetition after initial scores were controlled for.
1.3.3.1. Summary: Impact of reading accuracy development on oral language There is little research on the effect that reading accuracy may have on oral language development. The studies that have been conducted focus on phonological skills and fall into two categories: those looking at the effect of life-long illiteracy and those looking at reading accuracy and oral language development in childhood. Individuals who have not received reading instruction are disadvantaged on tasks which involve segmenting spoken words or nonwords, and their patterns of brain activity suggest that, unlike adults who have learnt to read, a co-ordinated neural circuit is not activated during these tasks. During childhood, reading accuracy predicts development on nonword repetition tasks that, again, benefit from segmenting spoken stimuli. Together with the evidence reviewed above, this suggests the presence of highly interactive spoken and written language processing systems.