A sociotonetic study of Lalo tone split in progress

Since Labov’s early work (e.g., 1963, 1966), sociolinguists have frequently examined change in progress on the segmental level, but much less is known about tone change in progress. The present study finds evidence of a tone split in progress in Lalo, a Tibeto-Burman language of China. While many of the world’s tone languages show historical evidence of tone splits, to our knowledge this is the first time that a tone split has been observed while it is occurring, making it possible to closely examine phonological, social, and perceptual factors. In this sociotonetic study of Lalo, 2,938 tone tokens were extracted from recordings of 38 speakers and analyzed in terms of age, sex, and educational level. Multifactorial analyses show that the temporal extent of voiced stops’ depression of Tone 1 F0 is increasing in apparent time, especially among women, while VOT of voiced stops is decreasing as educational levels improve, giving speakers more contact with Mandarin Chinese. The same 38 speakers were also given a perceptual identification task in which F0 was systematically adjusted. Mixed-effects modeling showed that listeners used multiple acoustic cues (consonant voicing, F0 onset, and F0 shape) to identify the voiced initial. These findings suggest that Lalo is undergoing a tone split that follows Beddor’s (2009) coarticulatory path to sound change.