Does the Auditory Saltation Stimulus Distinguish Dyslexic From Competently Reading Adults?

Abstract

Where the auditory saltation illusion has been used as a measure of auditory temporal processing (ATP) in dyslexia, conflicting results have been apparent (cf. R. Hari & P. Kiesilä, 1996; M. Kronbichler, F. Hutzler, & H. Wimmer, 2002). This study sought to re-examine these findings by investigating whether dyslexia is characterized by poor saltation task performance and whether saltation thresholds are related to reading and phonological processing within groups of either dyslexic or competent readers. Nineteen dyslexic and 20 competently reading adults (18-64 years of age) participated. Participants completed 2 runs of a 2-alternative forced-choice saltation task, along with standard measures of reading and phonological processing. Although overall poorer saltation thresholds were apparent in the dyslexic group, the threshold distributions overlapped considerably, with thresholds alone unable to predict group membership at a level significantly greater than chance. Neither strong nor significant correlations were observed among saltation thresholds, reading, and phonological processing skills within either group. The results of this study do not support suggestions of impaired ATP in dyslexia or associations among ATP, reading, and phonological processing. However, it is proposed that increased within- and between-subject variability in auditory thresholds might be a more valuable marker of dyslexia than the thresholds themselves. Implications of this observation for dyslexia research are discussed.