Disentangling the roles of formant proximity and stimulus prototypicality in adult vowel perception.

Ying Ying Liu,Linda Polka,Matthew Masapollo,Lucie Ménard

doi:10.1121/10.0003041

Abstract

The present investigation examined the extent to which asymmetries in vowel perception derive from a sensitivity to focalization (formant proximity), stimulus prototypicality, or both. English-speaking adults identified, rated, and discriminated a vowel series that spanned a less-focal/prototypic English /u/ and a more-focal/prototypic French /u/ exemplar. Discrimination pairs included one-step, two-step, and three-step intervals along the series. Asymmetries predicted by both focalization and prototype effects emerged when discrimination step-size was varied. The findings indicate that both generic/universal and language-specific biases shape vowel perception in adults; the latter are challenging to isolate without well-controlled stimuli and appropriately scaled discrimination tasks.

Highlights

A central issue in the field of speech perception is how listeners map the input acoustic signal onto phonetic categories
Considerable research has focused on addressing how this mapping is modified by linguistic experience over the course of development, beginning in early infancy (e.g., Kuhl et al, 2008). This emphasis on exploring languagespecific biases as opposed to more generic, language-universal speech processing biases stems in large part from research by Kuhl et al (Kuhl, 1991; Kuhl et al, 1992). Their studies with human infants, human adults, and monkeys revealed that early linguistic experience profoundly alters phonetic perception by decreasing discrimination sensitivity near nativelanguage phonetic category prototypes, and increasing sensitivity near boundaries between categories
We investigated whether directional asymmetries in adult vowel perception reveal language-specific biases favoring acoustic prototypes for native vowel categories, as well as language-general biases favoring more “focal” vowels

Summary

Introduction

A central issue in the field of speech perception is how listeners map the input acoustic signal onto phonetic categories. Considerable research has focused on addressing how this mapping is modified by linguistic experience over the course of development, beginning in early infancy (e.g., Kuhl et al, 2008) This emphasis on exploring languagespecific biases as opposed to more generic, language-universal speech processing biases stems in large part from research by Kuhl et al (Kuhl, 1991; Kuhl et al, 1992). There is a growing body of evidence that infants reared in diverse linguistic communities initially display generic biases or preferences that guide and constrain how infants perceive segmental elements in speech (Polka and Bohn, 2011), and that such biases continue to operate in adult language users independently of “language-specific” prototype categorization processes (Masapollo et al, 2017b). By late infancy and adulthood, linguistic experience has altered perception; analogous asymmetries are observed for nonnative contrasts but are mitigated for native contrasts which are typically perceived with near-perfect accuracy (e.g., Polka and Bohn, 2011; Tyler et al, 2014)

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