The influence of vowel laryngealisation and duration on the rhythmic grouping preferences of Zapotec speakers

Some studies of human rhythmic grouping biases (RGBs) have found that listeners tend to perceive greater duration as marking group endings, a “long-last” RGB that has been related to preboundary lengthening in languages. Accumulating evidence from adult and infant studies now suggests that duration-based RGBs are variable, learned, and sensitive to language input. If RGBs can be influenced by language background, then phonologically important features other than duration should be associated with RGBs. In this rhythmic grouping study, native speakers of Betaza Zapotec segmented sequences of syllables in which vowel duration and laryngealised phonation were varied. Results indicated a long-last RGB in all conditions in which duration was varied and a laryngeal-first bias when phonation was varied singly. When duration and phonation were co-varied in the same sequences, duration was the dominant predictor. However, when duration and phonation cues were opposed by alternating modal long and laryngealised short syllables, fewer long-last groupings suggested that in this context, listeners perceived laryngealised phonation as signalling finality. It is argued that in segmenting varied-phonation sequences, listeners were using knowledge of surface phonetic characteristics as opposed to knowledge of the lexical and phonological distribution of laryngealised vowels.