Behavioral and Cortical Indices of Typical and Atypical Development of Reading and Spelling Skills in Children : Evidence from Different Orthographies

Abstract

Are reading and spelling two sides of the same coin: in the acquisition of literacy? Or are they separate processes that have little in common? While these questions have been adequately addressed and evidence has become reasonably well established for European languages, little empirical research has been conducted for the Semitic languages, namely the Arabic language. The current thesis comprises three studies which generally aimed to identify some cortical and behavioral indices of typical and atypical development of fluent reading and spelling in children from different orthographies, namely Arabic and German. In study I, the developmental course of the relationship between fluent reading and spelling in the first three years of learning Arabic has been investigated with a consideration to evaluate potential gender differences. Analysis of data showed significant developments in literacy skills across age and a significant male advantage in literacy measures pronounced only in first graders. Further analysis of first grade data indicates a potential role of visualization and spatial abilities in the interplay between fluent reading and spelling in the early stages of literacy acquisition, but not in later grades. High correlations were found between fluent reading and spelling and, interestingly, spelling accuracy develops earlier than fluent reading, suggesting that spelling drives both the alphabetic and orthographic phases in learning Arabic. In study II, a representative sample of 1106 Arabic-speaking third graders were screened for their fluent reading and spelling abilities and their general level of functioning. Based on a two year behind grade level as a cut-off score, the prevalence of dyslexic children was estimated to be 8.1%. Based on the 16 percentile, the overall prevalence of the three impaired groups - good readers-poor spellers, poor spellers-good readers, poor readers-poor spellers - was 1.1%, .9% and 12.6%, respectively. The estimated incidence rate (8%-15%) of children suffering reading or/and spelling disorders is, surprisingly, high for Arabic and calls for specific attention to this problem in Arabic-speaking countries. Interestingly, less dissociations were observed between fluent reading and spelling in Arabic compared to the ones reported for European languages (e.g., German, French). In study III, an MEG study, we tested to see if temporal integration is reflected as oscillatory activity in different frequency bands. Therefore, we mapped focal slow waves in the delta (1.5-4Hz) frequency band, using magnetoencephalographic (MEG) source imaging in a sample of 19 dyslexic children with poor categorical perception and 14 controls while listening passively to syllables /ba/ and /da/. Dyslexic children with poor categorical perception differ significantly in the density of magnetic slow waves produced by the two hemispheres. To illustrate, dyslexic children with poor categorical perception showed elevated production of focally-generated slow waves (1-4Hz) predominately in the left hemisphere as compared to controls. The results suggest altered segmentation processes of speech sounds in a subset of children with dyslexia. Based on the findings of the current thesis, we draw the conclusion that the orthographic characteristics of a language have an impact on the typical and atypical development of reading and spelling both at the behavioral and the cortical level.