Paper short abstract:

A mysterious discrepancy in the prevalence of English and Japanese dyslexic populations is led to strengthening the mora-basic hypothesis that the moraic rhythm serves as a universal prosodic frame. This conforms to a human neurobiological restriction inclined toward a synchronized behavior.

Paper long abstract:

The neurobiological disorder called dyslexia (< Greek dys- 'impaired' + lexis 'word') is a specific learning disability that affects only literacy skills. It has been generally agreed that congenital form of dyslexia (termed developmental dyslexia) stems from a particular problem in language acquisition affecting phonological awareness. However, the exact nature of phonological awareness has not been made all clear.

This paper spotlights the mysterious discrepancy in the prevalence of dyslexic populations between the English-speaking world and the Japanese-speaking world; namely the figure as high as 15% or even more for the former and the figure as low as 2% or even less for the latter. On the basis of English dyslexic reading marked by an overproduction of CV-units in the absence of VC-units, the discrepancy is shown to be due to differences in prosodic structures between the two languages. For rhyme(VC)-oriented languages such as English, the readers must have rhyme-awareness which allows them to depict the unit rhyme through prosodic restructuring from CV-C to C-VC. A failure to have rhyme-awareness manifests as phonological dyslexia. For mora(CV)-oriented, rhyme-less languages such as Japanese, rhyme-awareness (and thus the prosodic restructuring) is irrelevant. Consequently, phonological dyslexia is largely undetected. In other words, phonological dyslexia is hidden in mora-based languages, but predicted to surface in ESL/EFL classroom. Low proficiency of the ESL/EFL students might be due to their having developmental dyslexia, which calls for special consideration to meet the students' specific needs.

The paper furthermore explores neurological explanation of the failure in prosodic restructuring. It is shown that phonological dyslexia is a cognitive disorder of neurobiological origin which cannot bear a cognitive load imposed on the suggested prosodic restructuring in the affected child's brain. The paper reaches to strengthen the mora-basic hypothesis that mora, which is formed by coarticulation of consonants and vowels, serves the elementary prosodic frame of all languages of the world. It is suggested that the mora-basic hypothesis conforms to a human neurological restriction inclined toward a synchronized behavior that had been acquired in the process of human evolution.