Periodic Reporting for period 5 - EVOTONE (The emergence and evolution of linguistic tone)
Période du rapport: 2023-08-01 au 2025-05-31
The focus of EVOTONE is on the origin, acquisition, and evolution of linguistic tone: the use of pitch to distinguish between the meaning of words. Despite the global presence and typological ubiquity of tone, there has never been a systematic analysis of the principles that govern the evolution of tone systems. Linguists still do not have a complete phonetic, structural, and psychological model that explains how and why tones emerge (or fail to emerge) in language after language, and how they evolve once they are formed. This research is important because it contributes to our fundamental understanding of language variation and change. Understanding how languages do and don’t differ, and how they change over time, provides a way to better trace historical linguistic shifts, account for contemporary linguistic differences between groups, and understand the factors driving language evolution. Linguistic tone is just one feature of human language, but because it is such a common and widespread one, and because it has emerged so recently (relatively speaking) in so many languages, studying its emergence and evolution helps us understand the limits of language variation and change more generally.
The EVOTONE project had three objectives: first, to provide a new, empirically based foundation for the origin and typology of tone systems; second, to study how structural and phonetic factors interact in sound change; third, to develop the first empirically grounded set of principles for tonal evolution. We addressed these using a combination of linguistic fieldwork, acoustic-phonetic laboratory studies, and computational analysis of language data at scale, allowing us to developed a more nuanced understanding of how tone is produced and perceived. This is not only of abstract scientific interest, but will help drive substantial improvements to speech technology – automated recognition, understanding, transcription, and production of human speech – for millions of speakers of languages that are typically marginalized because they have linguistic characteristics, such as the interaction between tone and phonation, that are not addressed by mainstream, national-language technological development.
The EVOTONE project had three objectives: first, to provide a new, empirically based foundation for the origin and typology of tone systems; second, to study how structural and phonetic factors interact in sound change; third, to develop the first empirically grounded set of principles for tonal evolution. We addressed these using a combination of linguistic fieldwork, acoustic-phonetic laboratory studies, and computational analysis of language data at scale, allowing us to developed a more nuanced understanding of how tone is produced and perceived. This is not only of abstract scientific interest, but will help drive substantial improvements to speech technology – automated recognition, understanding, transcription, and production of human speech – for millions of speakers of languages that are typically marginalized because they have linguistic characteristics, such as the interaction between tone and phonation, that are not addressed by mainstream, national-language technological development.
Over the course of the project, we conducted a number of experimental studies and undertaken data collection from a variety of languages, including non-tonal languages like French, Italian, German, and English; tonal languages of East and Southeast Asia, like Thai and Cantonese; and languages at various stages of tonal development such as Mon and Khmu. Through these studies, we gained a better understanding of how the acoustic properties of consonants and vowels come to be reinterpreted as tones. One important finding is that the emergence of tone is likely driven by abrupt shifts in the availability of certain acoustic dimensions, rather than by a gradual enhancement of those properties. Our data also indicate a substantial role for individual differences in both articulatory as well as perceptual strategies.
To extend our understanding of how tones change over time, we focused on variation and change of lexical tones in Thai. In addition to assembling a corpus of spoken Thai encompassing speakers from diverse range of ages and backgrounds, we leveraged archival data to study how the tonal systems of individuals change over their lifetimes, and conducted studies of how tones vary with rate and context. We found considerable structured variability in the tone systems of speakers of different generations, consistent with the idea that changes to tone systems take place abruptly when one tonal trajectory is replaced by another.
Supporting both of the above aspects, we analysed role of structural factors in tonal emergence and evolution using a custom collection of lexical resources and associated software tools. This approach allowed us to precisely quantify the structural aspects of tone systems that remain stable across generations, contributing to a more comprehensive typology of tone systems.
To extend our understanding of how tones change over time, we focused on variation and change of lexical tones in Thai. In addition to assembling a corpus of spoken Thai encompassing speakers from diverse range of ages and backgrounds, we leveraged archival data to study how the tonal systems of individuals change over their lifetimes, and conducted studies of how tones vary with rate and context. We found considerable structured variability in the tone systems of speakers of different generations, consistent with the idea that changes to tone systems take place abruptly when one tonal trajectory is replaced by another.
Supporting both of the above aspects, we analysed role of structural factors in tonal emergence and evolution using a custom collection of lexical resources and associated software tools. This approach allowed us to precisely quantify the structural aspects of tone systems that remain stable across generations, contributing to a more comprehensive typology of tone systems.
Our experimental work on the relationship between speech production and speech perception has pushed forward the state of the art in the field, leading to a better understanding the conditions under which it is favorable for tones to emerge. We have conducted instrumental studies on less commonly-studied languages and rare sound patterns, giving us new insights into the pre-conditions necessary or favourable for linguistic tone to emerge. Our digitisation and normalisation of pre-existing material on tonal systems has facilitated statistical analysis of tone systems on a scale previously impossible, leading to new insights into the regularities and limits of tonal variability.