Orthographic depth has been studied intensively as one of the sources of cross-linguistic differences in reading, and yet there has been little detailed analysis of what is meant by orthographic depth. Here we propose that orthographic depth is a conglomerate of two separate constructs: the complexity of print-to-speech correspondences and the unpredictability of the derivation of the pronunciations of words on the basis of their orthography. We show that on a linguistic level, these two concepts can be dissociated. Furthermore, we make different predictions about how the two concepts would affect skilled reading and reading acquisition. We argue that refining the definition of orthographic depth opens up new research questions. Addressing these can provide insights into the specific mechanisms by which language-level orthographic properties affect cognitive processes underlying reading.
The self-teaching hypothesis describes how children progress toward skilled sight-word reading. It proposes that children do this via phonological recoding with assistance from contextual cues, to identify the target pronunciation for a novel letter string, and in so doing create an opportunity to self-teach new orthographic knowledge. We present a new computational implementation of self-teaching within the dual-route cascaded (DRC) model of reading aloud, and we explore how decoding and contextual cues can work together to enable accurate self-teaching under a variety of circumstances. The new model (ST-DRC) uses DRC's sublexical route and the interactivity between the lexical and sublexical routes to simulate phonological recoding. Known spoken words are activated in response to novel printed words, triggering an opportunity for orthographic learning, which is the basis for skilled sight-word reading. ST-DRC also includes new computational mechanisms for simulating how contextual information aids word identification, and it demonstrates how partial decoding and ambiguous context interact to achieve irregular-word learning. Beyond modeling orthographic learning and self-teaching, ST-DRC's performance suggests new avenues for empirical research on how difficult word classes such as homographs and potentiophones are learned.
Digraphs are graphemes that are composed of two letters like the "ou" in "soup". We hypothesized that the serial-reading strategy of dyslexic readers might interfere with the processing of digraphs. We used a letter-detection task to compare the processing of vowel digraphs in dyslexic and typical-reading children. Both groups were found to be slower in detecting a letter within a vowel digraph than in detecting a letter of a single-letter grapheme. The slower response to target letters embedded in a digraph was position independent in both groups. We also found that dyslexic children did not differ from typical-reading children in the detection of letters in words. These results indicate that typical-reading and dyslexic children process vowel digraphs as perceptual units and that dyslexic children do not show impairments in this early visual process.
The current study examined the use of sublexical clusters in normal and dyslexic readers. We focused primarily on onset consonantal clusters, but the use of rimes and digraphs was also considered. A segmentation paradigm, the separation of two adjacent letters in a word by a nonletter symbol, was used. We hypothesized that the effect of this distortion on reading would be larger if two adjacent letters functioned as a cluster. In the first study, naming and lexical decision tasks were administered to 24 normal reading and 24 dyslexic fourth-grade children. In a second study, the same tasks were administered to 24 skilled adult readers. The results did not support the use of consonantal onsets and rimes during reading. However, we did find that digraphs were used, because their distortion had a relatively large effect on reading speed. This effect was similar in normal and dyslexic readers.Sublexical clusters are units that are larger than one letter but smaller than a word; they pertain to any combination of letters including digraphs; consonant clusters; and multiletter onsets, codas, and rimes. In the study presented here, we examined whether such clusters are acquired during reading acquisition. This issue is of theoretical and practical importance.Current models of skilled reading differ in the extent and way in which they represent sublexical clusters. In several connectionist models sublexical clusters have been explicitly built into the model or are an emergent property of the (statistical
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