Humanities and Social Sciences at Katholieke Universiteit Leuven, Belgium
Temporal auditory processing and speech perception as possible underlying deficits of the phonological problems in persons with dyslexia
Mapping graphemes to phonemes (the essence of reading) builds upon phonological awareness of the child, i.e. the consciousness of the sound structure of spoken language and the skill to manipulate it. Preschool children manipulate speech mainly at the syllable level. Only during reading acquisition phoneme awareness emerges and explicit phoneme representations develop. However, in order to develop clear phonological representations at syllable and phoneme level, the auditory system must be able to accurately process dynamic acoustic cues that are crucial for speech perception. Because of the importance of auditory sensitivity in reading acquisition, auditory processing and speech perception skills have received increasing attention in relation to dyslexia. Yet, only little evidence exists on the causal influence of these skills on reading development and on their specific nature. Therefore in 2003, we started a longitudinal project starting before the formal instruction of reading until the end of primary school. This project demonstrated that children with dyslexia have pre-reading deficits in auditory processing, speech perception and phonology, but more importantly, that basal auditory temporal processing and speech perception in kindergarten uniquely contribute to growth in reading ability. This is the first study that demonstrates that auditory processing and speech perception impairments in dyslexia are not merely an epiphenomenon of reading failure but that they precede and possibly contribute to the reading development. In a second cross-sectional project, involving 12-year-olds and adults diagnosed with dyslexia, we further investigated the precise nature of their auditory and speech perception problems. More specifically, by applying a balanced design we investigated whether the deficit is specific to speech and/or specific to temporal processing. Results show that both 12-year-olds and adults with dyslexia have an auditory temporal processing deficit which is not speech-specific.