Department of Linguistics
sanker [at] stanford [dot] edu
My research focuses on phonetic detail within phonology and how it fits into representations, establishing phonetic correlates of contrasts in production and testing how they influence perception and how they can shift based on experimental manipulations.
My second focus is on sound change. Modern perception and production data, in combination with traditional reconstruction and philology, can help establish pathways of diachronic developments.
Phonetics and Recording Methods in a Pandemic
Because of restrictions on travel and in-person research during the Covid-19 pandemic, many researchers have started making remote recordings, using a range of methods. It is important to know how these methods might affect acoustic measurements, particularly for underdocumented languages, but also in any phonetic research. Variation might arise either because of different recording devices or because of the software used to make recordings. In a collaborative project, I led the Yale fieldwork group in investigating how varied recording methods impact phonetic measurements. Different recording devices and software programs have a substantial impact on many of the measurements that we tested, including measurements of duration, frequency, and aperiodic noise.
Phonetics in Phonology
Phonetic details in the phonological representation are linked not just with individual sounds but also connected to sounds with shared features. I demonstrate that shifts are generalized at the featural level: Exposing listeners to raised or lowered F1 or F2 in one vowel produces corresponding shifts in vowels that match in height or backness, respectively.
I also test how listeners normalize for different talkers' vowel spaces based on exposure to the same absolute formant value in vowels produced by different speakers. Listeners extend shifted formants across speakers; their subsequent perception of a novel talker reflects the relative formants of exposure stimuli based the training talker's apparent vowel space.
There is less evidence for word-specific phonetic details. Listeners cannot reliably distinguish between homophone mates, but recent exposure to these words increases accuracy, suggesting that training draws listeners' attention to differences caused by factors like emotional valence. Outside of homophones, repetition effects suggest that most frequency-correlated phonetic variation is best explained by how frequency interacts with lexical access.
Speakers have a limited ability to learn new word-specific targets; exposure to stimuli manipulated in opposing directions in different words only produces word-specific shifts with few words and many repetitions. While this suggests that listeners do store word-specific phonetic details, those targets are usually outweighed by targets shared at the phonological level.
I also look at the bundle of acoustic cues used to characterize coda voicing. The acoustic correlates vary across languages, and also vary in perceptual usage. In particular, I tease apart two ways that acoustic cues are reflected in perception: their influence in identifications of the relevant contrast, and compensation for the expected relationship when identifying the cue itself. The different behaviors of these effects suggest that there are two types of cue representation: fully phonologized cues, reflected in both effects, and awareness of a gradient probabilistic relationship, which produces much weaker compensation.
Evidence for Sound Changes
Experimental data, in combination with traditional comparative methods, can elucidate questions about sound change, and in turn, patterns of sound change can further our understanding of biases in phonological interpretation of phonetic input. There are broad parallels between diachronic developments and synchronic patterns of perception and production, which make experimental data a useful source of complementary evidence for reconstructions.
One pattern that I have investigated is voicing-conditioned vowel duration; some correlates of coda voicing -- spectral tilt and intensity contour -- provide a likely pathway for how voicing-conditioned vowel duration develops. I examine how these vowel characteristics are influenced by coda voicing and how these characteristics in turn influence perceived vowel duration. While listeners compensate for the duration expected based on the coda, there are different effects when codas are removed.Vowels that had been produced with voiced codas are perceived as longer than vowels produced with voiceless codas.
I also use synchronic parallels to help test specific reconstructions, which is particularly useful for changes without many clear reconstructed parallels, such as the developments of the Proto-Indo-European laryngeals, which I investigated in my dissertation. More recently, I demonstrated a parallel for the sound change proposed in Winter's Law, with vowel lengthening before voiced unaspirated stops and not before voiced aspirated stops. While Hindi is often taken as representative of how voiced aspirated stops influence vowel duration, I demonstrate that Telugu differs from Hindi and provides a duration pattern that parallels Winter's Law. The different realizations of voiced aspirated stops in Hindi and Telugu further help illustrate crucial phonetic differences in sounds that are often treated as equivalent.
I have some more traditional reconstruction projects, particularly combining comparative reconstruction and written records to reconstruct sound changes and synchronic patterns in ancient languages of the Near East.
Currently I am part of a group studying A'ingae, a South American language isolate; we have produced the first instrumentally based overview of its phonological system and continue to elucidate both areally motivated characteristics of its phonology and unique characteristics, such as narrative use of syllable-level falsetto.
As part of my collaboration with the A'ingae fieldwork project, we have been working on reconstructing phonological changes. Although A'ingae has no known linguistic relatives, synchronic allomorphy and limited distributions of sounds suggest several sound changes that substantially restructured the system, including development of contrastive prenasalized stops and development of vowel nasality.