Impaired Statistical Learning in Developmental Dyslexia.

Yafit Gabay,Lori L Holt,Erik D Thiessen

doi:10.1044/2015_jslhr-l-14-0324

Yafit Gabay, Lori L Holt + Show 1 more

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https://doi.org/10.1044/2015_jslhr-l-14-0324

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Abstract

Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined if individuals with DD are capable of extracting statistical regularities across sequences of passively experienced speech and nonspeech sounds. Such statistical learning is believed to be domain-general, to draw upon procedural learning systems, and to relate to language outcomes. DD and control groups were familiarized with a continuous stream of syllables or sine-wave tones, the ordering of which was defined by high or low transitional probabilities across adjacent stimulus pairs. Participants subsequently judged two 3-stimulus test items with either high or low statistical coherence as being the most similar to the sounds heard during familiarization. As with control participants, the DD group was sensitive to the transitional probability structure of the familiarization materials as evidenced by above-chance performance. However, the performance of participants with DD was significantly poorer than controls across linguistic and nonlinguistic stimuli. In addition, reading-related measures were significantly correlated with statistical learning performance of both speech and nonspeech material. Results are discussed in light of procedural learning impairments among participants with DD.

Highlights

Developmental dyslexia (DD) is commonly thought to arise from phonological impairments
It should be noted that this equivalence was achieved, on the basis of prior research (Saffran et al, 1999), via small methodological differences in the presentation rate of the speech and nonspeech materials
Learners with DD were impaired on sequential statistical learning for both speech and nonspeech materials

Summary

Introduction

Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. Because the number of phonology– orthography correspondences is vast (more than 1,000 rules according to the dual route cascade model of reading; Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001), effective Consistent with this claim, Arciuli and Simpson (2012) observed that reading abilities among both adults and children are highly correlated with the ability to extract visual statistical structure from the environment. Evans, Saffran, and Robe-Torres (2009) have demonstrated that the ability to track regularities is positively correlated with vocabulary growth among children Taken together, these independent observations suggest that sensitivity to statistical regularities may impact reading development by enabling detection of probabilistic correspondences among letters and phonemes and the detection of regularities that exist among letters (transitional probabilities between letters). It may enhance vocabulary growth, which, in turn, can contribute to reading performance (Biemiller, 2003)

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