Information density and vowel dispersion in the productions of Bulgarian L2 speakers of German

Abstract

We investigated the influence of information density (ID) on vowel space size in L2. Vowel dispersion was measured for the stressed tense vowels /i:, o:, a:/ and their lax counterpart /I, O, a/ in read speech from six German speakers, six advanced and six intermediate Bulgarian speakers of German. The Euclidean distance between center of the vowel space and formant values for each speaker was used as a measure for vowel dispersion. ID was calculated as the surprisal of the triphone of the preceding context. We found a significant positive correlation between surprisal and vowel dispersion in German native speakers. The advanced L2 speakers showed a significant positive relationship between these two measures, while this was not observed in intermediate L2 vowel productions. The intermediate speakers raised their vowel space, reflecting native Bulgarian vowel raising in unstressed positions.