More on the articulation of devoiced [u] in Tokyo Japanese: effects of surrounding consonants.

Past work investigating the lingual articulation of devoiced vowels in Tokyo Japanese has revealed optional but categorical deletion. Some devoiced vowels retained a full lingual target, just like their voiced counterparts, whereas others showed trajectories that are best modelled as targetless, i.e., linear interpolation between the surrounding vowels. The current study explored the hypothesis that this probabilistic deletion is modulated by the identity of the surrounding consonants. A new EMA experiment with an extended stimulus set replicates the core finding of Shaw, Jason & Shigeto Kawahara. 2018b. The lingual gesture of devoiced [u] in Japanese. Journal of Phonetics 66. 100-119. DOI:https://doi.org/10.1016/j.wocn.2017.09.007 that Japanese devoiced [u] sometimes lacks a tongue body raising gesture. The current results moreover show that surrounding consonants do indeed affect the probability of tongue dorsum targetlessness. We found that deletion of devoiced vowels is affected by the place of articulation of the preceding consonant; deletion is more likely following a coronal fricative than a labial fricative. Additionally, we found that the manner combination of the flanking consonants, fricative-fricative versus fricative-stop, also has an effect, at least for some speakers; however, unlike the effect of C1 place, the direction of the manner combination effect varies across speakers with some deleting more often in fricative-stop environments and others more often in fricative-fricative environments.

Prosody leaks into the memories of words.

The average predictability (aka informativity) of a word in context has been shown to condition word duration (Seyfarth, 2014). All else being equal, words that tend to occur in more predictable environments are shorter than words that tend to occur in less predictable environments. One account of the informativity effect on duration is that the acoustic details of probabilistic reduction are stored as part of a word's mental representation. Other research has argued that predictability effects are tied to prosodic structure in integral ways. With the aim of assessing a potential prosodic basis for informativity effects in speech production, this study extends past work in two directions; it investigated informativity effects in another large language, Mandarin Chinese, and broadened the study beyond word duration to additional acoustic dimensions, pitch and intensity, known to index prosodic prominence. The acoustic information of content words was extracted from a large telephone conversation speech corpus with over 400,000 tokens and 6000 word types spoken by 1655 individuals and analyzed for the effect of informativity using frequency statistics estimated from a 431 million word subtitle corpus. Results indicated that words with low informativity have shorter durations, replicating the effect found in English. In addition, informativity had significant effects on maximum pitch and intensity, two phonetic dimensions related to prosodic prominence. Extending this interpretation, these results suggest that predictability is closely linked to prosodic prominence, and that the lexical representation of a word includes phonetic details associated with its average prosodic prominence in discourse. In other words, the lexicon absorbs prosodic influences on speech production.

Effects of vowel coproduction on the timecourse of tone recognition.

Vowel contrasts tend to be perceived independently of pitch modulation, but it is not known whether pitch can be perceived independently of vowel quality. This issue was investigated in the context of a lexical tone language, Mandarin Chinese, using a printed word version of the visual world paradigm. Eye movements to four printed words were tracked while listeners heard target words that differed from competitors only in tone (test condition) or also in onset consonant and vowel (control condition). Results showed that the timecourse of tone recognition is influenced by vowel quality for high, low, and rising tones. For these tones, the time for the eyes to converge on the target word in the test condition (relative to control) depended on the vowel with which the tone was coarticulated with /a/ and /i/ supporting faster recognition of high, low, and rising tones than /u/. These patterns are consistent with the hypothesis that tone-conditioned variation in the articulation of /a/ and /i/ facilitates rapid recognition of tones. The one exception to this general pattern-no effect of vowel quality on falling tone perception-may be due to fortuitous amplification of the harmonics relevant for pitch perception in this context.

Spatially Conditioned Speech Timing: Evidence and Implications.

Patterns of relative timing between consonants and vowels appear to be conditioned in part by phonological structure, such as syllables, a finding captured naturally by the two-level feedforward model of Articulatory Phonology (AP). In AP, phonological form - gestures and the coordination relations between them - receive an invariant description at the inter-gestural level. The inter-articulator level actuates gestures, receiving activation from the inter-gestural level and resolving competing demands on articulators. Within this architecture, the inter-gestural level is blind to the location of articulators in space. A key prediction is that intergestural timing is stable across variation in the spatial position of articulators. We tested this prediction by conducting an Electromagnetic Articulography (EMA) study of Mandarin speakers producing CV monosyllables, consisting of labial consonants and back vowels in isolation. Across observed variation in the spatial position of the tongue body before each syllable, we investigated whether inter-gestural timing between the lips, for the consonant, and the tongue body, for the vowel, remained stable, as is predicted by feedforward control, or whether timing varied with the spatial position of the tongue at the onset of movement. Results indicated a correlation between the initial position of the tongue gesture for the vowel and C-V timing, indicating that inter-gestural timing is sensitive to the position of the articulators, possibly relying on somatosensory feedback. Implications of these results and possible accounts within the Articulatory Phonology framework are discussed.

Effects of Surprisal and Entropy on Vowel Duration in Japanese.

Research on English and other languages has shown that syllables and words that contain more information tend to be produced with longer duration. This research is evolving into a general thesis that speakers articulate linguistic units with more information more robustly. While this hypothesis seems plausible from the perspective of communicative efficiency, previous support for it has come mainly from English and some other Indo-European languages. Moreover, most previous studies focus on global effects, such as the interaction of word duration and sentential/semantic predictability. The current study is focused at the level of phonotactics, exploring the effects of local predictability on vowel duration in Japanese, using the Corpus of Spontaneous Japanese. To examine gradient consonant-vowel phonotactics within a consonant-vowel-mora, consonant-conditioned Surprisal and Shannon Entropy were calculated, and their effects on vowel duration were examined, together with other linguistic factors that are known from previous research to affect vowel duration. Results show significant effects of both Surprisal and Entropy, as well as notable interactions with vowel length and vowel quality. The effect of Entropy is stronger on peripheral vowels than on central vowels. Surprisal has a stronger positive effect on short vowels than on long vowels. We interpret the main patterns and the interactions by conceptualizing Surprisal as an index of motor fluency and Entropy as an index of competition in vowel selection.

A comparison of acoustic and articulatory methods for analyzing vowel differences across dialects: Data from American and Australian English.

In studies of dialect variation, the articulatory nature of vowels is sometimes inferred from formant values using the following heuristic: F1 is inversely correlated with tongue height and F2 is inversely correlated with tongue backness. This study compared vowel formants and corresponding lingual articulation in two dialects of English, standard North American English, and Australian English. Five speakers of North American English and four speakers of Australian English were recorded producing multiple repetitions of ten monophthongs embedded in the /sVd/ context. Simultaneous articulatory data were collected using electromagnetic articulography. Results show that there are significant correlations between tongue position and formants in the direction predicted by the heuristic but also that the relations implied by the heuristic break down under specific conditions. Articulatory vowel spaces, based on tongue dorsum position, and acoustic vowel spaces, based on formants, show systematic misalignment due in part to the influence of other articulatory factors, including lip rounding and tongue curvature on formant values. Incorporating these dimensions into dialect comparison yields a richer description and a more robust understanding of how vowel formant patterns are reproduced within and across dialects.

Influences of Tone on Vowel Articulation in Mandarin Chinese.

Purpose: Models of speech production often abstract away from shared physiology in pitch control and lingual articulation, positing independent control of tone and vowel units. We assess the validity of this assumption in Mandarin Chinese by evaluating the stability of lingual articulation for vowels across variation in tone. Method: Electromagnetic articulography was used to track flesh points on the tongue (tip, body, dorsum), lips, and jaw while native Mandarin speakers (n = 6) produced 3 vowels, /pa/, /pi/, /pu/, combined with 4 Mandarin tones: T1 "high," T2 "rising," T3 "low," and T4 "falling." Results: Consistent with physiological expectations, tones that begin low, T2 and T3, conditioned a lower position of the tongue body for the vowel /a/. For the vowel /i/, we found the opposite effect, whereby tones that begin low, T2 and T3, conditioned a higher tongue body position. Conclusions: The physiology of pitch control exerts systematic variation on the lingual articulation of /a/ across tones. The effects of tone on /i/ articulation are in the opposite direction predicted by physiological considerations. Physiologically arbitrary variation of the type observed for /i/ challenges the assumption that phonetic patterns can be determined by independent control of tone (source) and vowel (filter) production units.

Stochastic time models of syllable structure.

Drawing on phonology research within the generative linguistics tradition, stochastic methods, and notions from complex systems, we develop a modelling paradigm linking phonological structure, expressed in terms of syllables, to speech movement data acquired with 3D electromagnetic articulography and X-ray microbeam methods. The essential variable in the models is syllable structure. When mapped to discrete coordination topologies, syllabic organization imposes systematic patterns of variability on the temporal dynamics of speech articulation. We simulated these dynamics under different syllabic parses and evaluated simulations against experimental data from Arabic and English, two languages claimed to parse similar strings of segments into different syllabic structures. Model simulations replicated several key experimental results, including the fallibility of past phonetic heuristics for syllable structure, and exposed the range of conditions under which such heuristics remain valid. More importantly, the modelling approach consistently diagnosed syllable structure proving resilient to multiple sources of variability in experimental data including measurement variability, speaker variability, and contextual variability. Prospects for extensions of our modelling paradigm to acoustic data are also discussed.