The relationship between reading ability and categorical perception of spectrotemporal and spectral contrasts in children

Abstract

Behavioral evidence suggests that dyslexic readers are impaired in processing rapid temporal changes such as formant transitions. It is unclear if this possible impairment is attributable to the dynamic nature of a formant transition, the brevity of the cue, or a general deficit in categorical decision making. We tested categorical perception of speech in 30 children between the ages of 8 and 12 with a range of reading abilities (dyslexic, below average and above average readers) on two stimulus continua: (1) a /ba/-/da/ continuum, in which a 100-ms formant transition provides a spectrotemporal cue, and (2) a /sa/-/sha/ continuum with a purely spectral contrastive cue also lasting 100 ms. Two test conditions probed the interaction of working memory and categorical perception: a single-interval condition and an ABX paradigm. Children with dyslexia showed shallower psychometric functions and more lapses at the continuum endpoints compared to controls. There was no effect of stimulus continuum or test condition. This suggests that dyslexic children are not specifically impaired in their perception of formant transitions. Rather, dyslexic children may be subtly challenged in auditory coding of, or decision making about, temporally brief cues that may be either spectral or spectrotemporal in nature.