The gradient influence of temporal extent of coarticulation on vowel and speaker perception

Abstract

Coarticulation makes vowels in context acoustically different from context-free vowels. Listeners sometimes compensate by ascribing these acoustic effects to their source, but the conditions under which they do so have not yet been fully pinpointed. Ohala (1993) had suggested that acoustic effects which are temporally more distant from their source should be more susceptible to misattribution. In three experiments, we tested this hypothesis by varying the temporal extent of coda-triggered coarticulation on vowels and investigating its influence on two different perceptual behaviors: speaker-model representation and vowel-phoneme identification. Experiment 1 asked listeners to estimate speaker height based on /giC/ and /gɪC/ nonsense tokens produced by twelve female speakers. Results indicated a gradient effect: Within lax /ɪ/, greater temporal extent of coarticulation correlated with taller height judgments. Experiment 2a was similar, except that temporal extent of coarticulation in the tokens varied across a wider range of values than in Experiment 1. Results again indicated a gradient effect: Within lax /ɪ/, greater temporal extent of coarticulation correlated with taller height judgments. In Experiment 2b, listeners performed an AXB vowel-phoneme discrimination task. Results showed that greater temporal extent of coarticulation correlated with greater likelihood of listeners judging an intended /ɪ/ token to contain the vowel /ʌ/. Taken together, our results indicate that temporal extent of coarticulation affects both speaker-models and interpretation of vowel identity.

Keywords

• temporal dynamics
• coarticulation
• perceptual compensation
• speaker height perception
• vowel perception
• sound change