Enhanced Sensitivity to Subphonemic Segments in Dyslexia: A New Instance of Allophonic Perception

International audienceAlthough dyslexia can be individuated in many different ways, it has only three discernable sources: a visual deficit that affects the perception of letters, a phonological deficit that affects the perception of speech sounds, and an audiovisual deficit that disturbs the association of letters with speech sounds. However, the very nature of each of these core deficits remains debatable. The phonological deficit in dyslexia, which is generally attributed to a deficit of phonological awareness, might result from a specific mode of speech perception characterized by the use of allophonic (i.e., subphonemic) units. Here we will summarize the available evidence and present new data in support of the "allophonic theory" of dyslexia. Previous studies have shown that the dyslexia deficit in the categorical perception of phonemic features (e.g., the voicing contrast between /t/ and /d/) is due to the enhanced sensitivity to allophonic features (e.g., the difference between two variants of /d/). Another consequence of allophonic perception is that it should also give rise to an enhanced sensitivity to allophonic segments, such as those that take place within a consonant cluster. This latter prediction is validated by the data presented in this paper

Développement de la perception catégorielle des consonnes et implications pour l'étude de la dyslexie

La théorie allophonique veut que les dyslexiques perçoivent les sons de la parole non pas en phonèmes mais bien en allophones. Les implications de la théorie allophonique ont jusqu'à présent été testées en examinant la perception d'oppositions paradigmatiques (celles de voisement et de lieu d'articulation des consonnes) et ce afin de mettre en évidence une surdiscrimination de frontières allophoniques universelles, différentes des frontières phonémiques propres à une langue donnée. Ici, je tente d'abord de confirmer ces résultats pour aborder ensuite les implications de la perception allophonique sur les capacités de segmentation en phonèmes. L'objectif principal de cette thèse consiste à tester une autre prédiction de la théorie allophonique, à savoir que les dyslexiques devraient mieux percevoir les segments de parole intermédiaires entre deux phonèmes consécutifs. Cette capacité à percevoir des segments de parole infra-phonémiques sera qualifiée d'allophonie syntagmatique pour la distinguer de l'allophonie paradigmatique mise en évidence dans les recherches antérieures. Mes résultats apportent une confirmation de l'allophonie paradigmatique et mettent en évidence une allophonie syntagmatique chez des enfants dyslexiques, par comparaison avec les enfants neurotypiques plus jeunes mais de même niveau de lecture. Cette dernière forme d'allophonie est particulièrement robuste et fiable par rapport à l'allophonie paradigmatique, et elle a des implications encore plus évidentes pour l'apprentissage de lecture.According to allophonic theory, subjects suffering from dyslexia would perceive speech sounds not in phonemes, but in allophones. Up to now, the implications of the allophonic theory have been tested by examining the perception of paradigmatic oppositions (those of voicing and place of articulation in consonants), in order to evidence an overdiscrimination of universal allophonic boundaries, different from the phonemic boundaries specific to a particular language.The main objective of the present work is to test another prediction of the allophonic theory, namely the enhanced perception of segments located between consecutive phonemes. This enhanced perception of subphonemic segments will be called "syntagmatic" allophony to differentiate it from the "paradigmatic'1 one, already evidenced in previous research. The results of a first study confirm the previous findings on the allophonic perception of paradigmatic oppositions by dyslexic children, compared to neurotypical control children of the same reading level. The results of a second study show that the durational threshold for perceiving a vowel between two consonants is shorter in dyslexic vs. control children, thereby evidencing a syntagmatic allophony. The latter is especially robust and reliable compared to the paradigmatic allophony, and has even more straightforward implications for learning to read.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF