CATEGORICAL PERCEPTION IN DYSLEXIC AND

This paper concerns a study on the auditory perception of dyslexic adults compared to normal-reading controls. The stimulus material that was developed for this purpose consisted of three speech continua - the stop-consonant continuum (/b Ak/-/dAk/), the stop-consonant approximant continuum (/b Ak/-/wAk/) and the stop-consonant-fricative continuum (/ bAk/-/zAk/). The speech stimuli were based on natural speech of a woman. The three continua were used in an AX-discrimination test and a classification test with 12 dyslexic adults and 12 normally reading subjects. These categorical perception experiments were done to establish whether dyslexics process phoneme boundaries differently from normal readers. On several aspects the results of the dyslexic group differ clearly from those of the control group. Dyslexic subjects are in general less skilled than the control subjects in discriminating between the stimuli of a speech continuum. Furthermore, classification performance seems less categorical in dyslexic listeners. In both tasks dyslexics are also slower in giving their responses. As for the quality of the three speech continua, the results indicate that the /b Ak/-/dAk/ as well as the /b Ak/-/wAk/ continuum is suitable for further experimenting. Both continua are perceived categorically by all listeners. In future research the aim is to use these speech continua for measuring auditory perception and processing in children suffering from or at risk of developing dyslexia.

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