Directional asymmetries reveal a universal bias in adult vowel perception
Date
2017Author
Masapollo, Matthew
Polka, Linda
Molnar, Monika
Ménard, Lucie
Metadata
Show full item recordAbstract
Research on cross-language vowel perception in both infants and adults has shown that for many
vowel contrasts, discrimination is easier when the same pair of vowels is presented in one direction
compared to the reverse direction. According to one account, these directional asymmetries
reflect a universal bias favoring “focal” vowels (i.e., vowels whose adjacent formants are close
in frequency, which concentrates acoustic energy into a narrower spectral region). An alternative,
but not mutually exclusive, account is that such effects reflect an experience-dependent
bias favoring prototypical instances of native-language vowel categories. To disentangle the
effects of focalization and prototypicality, the authors first identified a certain location in
phonetic space where vowels were consistently categorized as /u/ by both Canadian-English and
Canadian-French listeners, but that nevertheless varied in their stimulus goodness (i.e., the best
Canadian-French /u/ exemplars were more focal compared to the best Canadian-English /u/
exemplars). In subsequent AX discrimination tests, both Canadian-English and Canadian-French
listeners performed better at discriminating changes from less to more focal /u/’s compared to
the reverse, regardless of variation in prototypicality. These findings demonstrate a universal
bias favoring vowels with greater formant convergence that operates independently of biases
related to language-specific prototype categorization.