Fine-tuning the Lingua Franca Core: The intelligibility of glottal stops and /d/-flaps

The motivation for this study was Jenkins’ (2000, 2007) call for a fine-tuning of the Lingua Franca Core (LFC), a set of pronunciation features that allegedly safeguard intelligibility in lingua franca contexts, where non-native speakers (NNSs) communicate mainly with other NNSs. Consonants figure prominently in this pronunciation syllabus, and the current study examined experimentally the international intelligibility of two consonant variants that are widespread in many native English accents: the glottal stop and /d/-flaps. 72 NNSs with seven different L1s participated in a listening task in which a matched-guise technique was employed and two positional variants of the glottal stop (before a pause, in word boundaries) and two positional variants of the /d/-flap (within words, in word boundaries) were tested. Intelligibility was analyzed as the number of tokens correctly identified in the listening task. The results revealed that the glottal stop was largely detrimental for intelligibility in the pre-pausal position, and the /d/-flap was especially unintelligible in word boundaries. These findings suggest that these two consonant variants, in at least two phonological positions, be added to the provisos of the consonantal inventory of the LFC in an effort to expand our knowledge of phonological lingua franca intelligibility.