In stress-based languages, metrical prominence asymmetries play an important role both in influencing phonological alternations (e.g. the English flapping rule) and in facilitating online speech processing, as they aid listeners in generating expectations for upcoming speech patterns (Breen et al. 2014, Brown et al. 2011; Dilley & McAuley 2008; Rothermich et al. 2012). African tone languages, which largely lack phonetic evidence of stress, have been argued not to require such prominence-based metrical alternations, despite the fact that they often display phonological patterns which seem to have a metrical basis (Hyman 2010). In this talk, I discuss two experimental projects examining metrical prominence asymmetries in Medʉmba, a Grassfields Bantu language, through the lens of speech timing.
The first project involves the use of a speech production task (the speech cycling paradigm; Cummins & Port 1998) which has participants repeat utterances at fixed speech rates in order to measure alignment patterns of syllables within an utterance. The results (Franich 2017, 2018) show that there are striking similarities in the temporal alignment behavior of syllables in stem-initial position in Medʉmba (a position which is thought to be associated with greater prominence across Bantu languages) and metrically-strong stressed syllables in English. Contextualizing these findings within a dynamical model of the prosodic hierarchy, I show that, despite differences in their acoustic realization, metrical prominence asymmetries are present in both languages. I discuss the theoretical implications of this finding in phonology as well as some possible broader applications it may have for the study of speech coordination and processing.
The second project presents pilot data from a series of lexical identification tasks with speakers of English and various West and Central African languages. Preliminary results (Franich, in progress) suggest that speakers of African languages, like English speakers, build metrical expectations which aid in speech perception. A key difference is found, however, in the way that speakers build metrical expectations in the context of an additional auditory stimulus, in this case, a metronome beat. In particular, while English listeners’ expectations seem to be facilitated by synchronous presentation of prominent syllables with a metronome beat, African listeners’ expectations are facilitated through asynchronous (‘off-beat’) presentation of prominent syllables with the beat.
This work makes three important contributions. First, it highlights the importance of metrical structure in shaping phonological patterns across languages, as well as the role of temporal structure in illuminating patterns of metrical prominence. Second, it demonstrates the crucial role that metrical prominence plays in both speech coordination and perception, even in the absence of stress. Third, the work shows how the relationship between grammar and predictive processes in speech perception is crucially mediated by the coordinative strategies we employ to interact with our environment.