Asymmetries in vowel perception: Do they arise from focalization, perceptual magnets, or both?

Abstract

While directional asymmetries are ubiquitous in cross-language studies of vowel perception, their underlying mechanisms have not been established. One hypothesis is that listeners display a universal perceptual bias favoring vowels with greater formant frequency convergence, or focalization (Polka and Bohn, 2011). A second, but not mutually exclusive, hypothesis is that listeners are biased toward prototypical vowel exemplars in their native language (Kuhl, 1993). In a test of these hypotheses, English listeners discriminated synthesized English /u/ and French /u/ vowels presented in pairs. While the French /u/ tokens exhibit greater formant convergence (between F1 and F2), English listeners have previously been shown to rate the English /u/ tokens as “better” instances of the category (Molnar, 2010). Preliminary results demonstrate that the degree of focalization affects vowel discrimination. When discriminating vowel changes presented in the direction going from the more focal (French) to less focal (English) /u/ vowels, English listeners' reaction times were slower, relative to the same changes presented in the reverse direction. These results suggest that listeners treat the more focal vowels as perceptual reference points. Additional data collection with French listeners is ongoing. The implications of these findings for theories of vowel perception will be discussed.