This dissertation investigates whether there are systematic individual differences in the perceptual weighting of frequency and duration speech cues for vowels and fricatives (and their non-speech analogues) among a dialectally homogeneous group of speakers. Many of the previous studies on individual differences have failed to control for the dialects of the subjects, which suggests that any individual differences that were found may be dialectal. Dialect production and perception tasks were included in this study to help ensure that subjects are not from dissimilar dialects. The main task for listeners was AX discrimination for four separate types of stimuli: sine wave vowels, narrowband fricatives, synthetic vowels, and synthetic fricatives. Vowel stimuli were based on the manipulation of duration and frequency of F1 for the vowels in “heed” and “hid”, while fricative stimuli were based on the manipulation of the fifth frequency centroid of the fricatives in “bath” and “bass”. Multidimensional scaling results indicate 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. Results of this study will be relevant to the fields of perception, feature phonology, dialectology, and language change. If subgroups can have different perceptions of speech (but similar productions), this questions what is needed to classify dialect continua, and the ratios of these subgroups changing over time can explain some language mergers and shifts.
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