Detection and identification of monaural and binaural pitch contours in dyslexic listeners

Binaural pitch stimuli were used in several recent studies to test for the presence of binaural auditory impairment in reading-disabled subjects. The outcome of three of these studies (Dougherty et al., 1998; Edwards et al., 2004; Chait et al., 2007) has been contradictory: Where the former two found that a majority of dyslexic subjects were unable to hear binaural pitch, the latter obtained a clear response of dyslexic listeners to Huggins’ pitch (HP) (Cramer and Huggins, 1958). The present study clarified whether impaired binaural pitch perception is found in dyslexia. Results from a pitch contour identification test, performed in 31 dyslexic listeners and 31 matched controls, clearly showed that dyslexics perceived HP as well as the controls. Both groups also showed comparable results with a similar-sounding, monaurally-detectable, pitch-evoking stimulus. However, nine of the dyslexic subjects had difficulty identifying pitch contours, independent of the stimulus used. The ability of subjects to correctly identify pitch contours was found to be significantly correlated to measures of frequency discrimination. This correlation may be attributed to the similarity of the experimental tasks and probably reflects impaired cognitive mechanisms related to auditory memory or auditory attention rather than impaired low-level auditory processing per se.