Longitudinal study of phonetic drift in L1 speech of late Czech-French bilinguals

This study investigates temporal development of phonetic drift (i.e., when L1 pronunciation is affected by acquiring an L2 language) in the L1 speech of four Czech university students (two female and two male) who went to study in Toulouse as part of the Erasmus programme. Having started studying L2 French at the age of twelve to sixteen, they are considered the so-called Czech-French late bilinguals. The subjects were recorded reading out a Czech text and producing semi-spontaneous speech in three sessions – immediately after their arrival, and then at the end of the first and the third month of their stay in France. Based on acoustic analyses, we statistically evaluated the formant frequencies of vowels, the spectral moments of the fricatives /ɦ/ and /x/, and the production frequency of schwa in the word-final position, which is a distinctive pronunciation feature for Toulouse French. Even though speech and its development are highly individual, we were able to witness certain pronunciation shifts regarding all the examined phones. However, the majority of statistically significant shifts were linked to the formant values of vowels.