Investigating the conditions on target-context assimilation in speech sound categorization
Amanda Rysling, John K. C. Kingston · The Journal of the Acoustical Society of America · 2019
Many studies have shown that listeners perceptually differentiate target sounds in categorization tasks from their neighboring context sounds, but some have shown that targets are perceptually assimilated to their contexts. We test the hypothesis that differentiation occurs in context-target order because the context is taken as the criterion for categorizing the target, but assimilation occurs in target-context order because the context's acoustics are parsed as target information. In our experiments, the target was a labial-to-coronal consonant continuum or a front-to-back vowel continuum in VC and CV strings, and the contexts were the other continuum's endpoints. As the second sound in VC or CV, the target differentiated from the preceding context: listeners responded "labial" or "back" more often after front vowels and coronal consonants, respectively. With a target V in VC, the target assimilated to the following context: listeners responded "back" more often before labial consonants. For C in CV, some listeners assimilated the consonant to the following vowel: they responded "labial" more often before back vowels. Others instead differentiated the consonant from the vowel: they responded "coronal" more often before back vowels. Follow-up experiments will determine the conditions in which a consonant assimilates to or differentiates from a following vowel.