The perception of English and Spanish vowels by native English and Spanish listeners: A multidimensional scaling analysis

A group of Spanish- and English-speaking listeners participated in a multidimensional scaling (MDS) study examining perceptual responses to three Spanish and seven English vowels. The vowel stimuli represented tokens of Spanish /i/, /e/, and /a/ and English /i/, /i/, /ei/, /ε/, /æ/, /inverted vee/, and /ɑ/. Each vowel had been spoken by three monolingual talkers of Spanish or English and all possible vowel pairs (405 pairs) were presented to listeners (excluding pairs representing the same vowel category). Thirty monolingual English listeners and thirty native Spanish listeners who had learned English as a second language rated these vowel pairs on a nine-point dissimilarity scale. These perceptual distances were then analyzed using the individual-differences version of ALSCAL. Results demonstrated that the English monolinguals used three underlying dimensions in rating vowels while the Spanish–English bilinguals used just two. The most salient perceptual dimension for both groups distinguished vowel height. However, for the English listeners, this dimension was most significantly correlated with duration and indicated a language-dependent sensitivity to this phonetic feature. The second dimension for the English listeners represented a front–back distinction, while the third reflected a central/noncentral distinction. For the Spanish listeners, the second dimension was less easily interpreted. However, the perceptual data for the Spanish listeners was more interpretable in terms of the distribution of the vowels in the two-dimensional perceptual plane. The vowels were distributed in terms of three separate vowel clusters, each cluster near the location of a Spanish vowel. Separate MDS analyses were carried out for subgroups of Spanish listeners who were relatively proficient or nonproficient in English. The vowel space of the proficient Spanish listeners was more Englishlike than that of the nonproficient Spanish listeners, suggesting that the perceptual dimensions used by listeners in identifying vowels may be gradually modified as proficiency in the second language improves.