Individual differences in speech and nonspeech perception of frequency and duration

Abstract

This study investigates whether there are systematic individual differences in the perceptual weighting of frequency and durational speech cues for vowels and fricatives (and their nonspeech analogs) among a dialectally homogeneous group of speakers. Listeners performed AX discrimination for four separate types of stimuli: sine wave vowels, narrow-band fricatives, synthetic vowels, and synthetic fricatives. Duration and F1 frequency were manipulated for the vowels in heed and hid, and duration and frequency of the fricative centroid in the F5 region were manipulated for the fricatives in bath and bass. Dialect production and perception tasks were included to ensure that subjects were not from dissimilar dialects. Multidimensional scaling results indicated that there are subgroups within a dialect that attend to frequency and duration differently, and that not all listeners use these cues consistently across dissimilar phones. If subgroups can have different perceptions of speech despite similar productions, this questions the requirements for classifying dialect continua. Furthermore, the ratios of these subgroups changing over time can explain some language mergers and shifts. Currently at Army Audiol. & Speech Ctr., Walter Reed Army Medical Ctr., Washington, D.C.