Lisa Davidson

Comparing tongue shapes from ultrasound imaging using smoothing spline analysis of variance.

Ultrasound imaging of the tongue is increasingly common in speech production research. However, there has been little standardization regarding the quantification and statistical analysis of ultrasound data. In linguistic studies, researchers may want to determine whether the tongue shape for an articulation under two different conditions (e.g., consonants in word-final versus word-medial position) is the same or different. This paper demonstrates how the smoothing spline ANOVA (SS ANOVA) can be applied to the comparison of tongue curves [Gu, Smoothing Spline ANOVA Models (Springer, New York, 2002)]. The SS ANOVA is a technique for determining whether or not there are significant differences between the smoothing splines that are the best fits for two data sets being compared. If the interaction term of the SS ANOVA model is statistically significant, then the groups have different shapes. Since the interaction may be significant even if only a small section of the curves are different (i.e., the tongue root is the same, but the tip of one group is raised), Bayesian confidence intervals are used to determine which sections of the curves are statistically different. SS ANOVAs are illustrated with some data comparing obstruents produced in word-final and word-medial coda position.

Phonology, phonetics, or frequency: Influences on the production of non-native sequences

Abstract This article examines the influence of phonetic and phonological factors and lexical frequency on accuracy and error types in the production of non-native phonotactics. In Experiment 1, English speakers were presented with non-native word-initial consonant clusters that were varied on several phonetic dimensions. Results showed that speakers are not equally accurate on the production of different illegal sequences. An analysis of lexical frequency statistics demonstrates that the frequency of these sequences in other positions across the lexicon does not correlate with accuracy. An explanation based on phonological knowledge is posited instead. A second experiment on the investigation of the strategies used to repair the illegal clusters indicated that speakers prefer schwa insertion. While previous research has assumed that such repairs are vowel epenthesis, a detailed acoustic analysis indicates that inserted schwas are significantly different than lexical schwas. These acoustic characteristics are compatible with articulatory evidence suggesting that there is a prohibition on applying canonical English consonant cluster coordination to phonotactically illegal sequences, leading speakers to “pull apart” the consonant gestures and causing a transitional schwa to appear on the acoustic record. The ramifications of these results for the role of an abstract phonological level in production are discussed.

Schwa Elision in Fast Speech: Segmental Deletion or Gestural Overlap?

Pretonic schwa elision in fast speech (e.g. potato -› [pt]ato, demolish -› [dm]olish) has been studied by both phonologists and phoneticians to understand how extralinguistic factors affect surface forms. Yet, both types of studies have major shortcomings. Phonological analyses attributing schwa elision to acrossthe- board segmental deletion have been based on researchers’ intuitions. Phonetic accounts proposing that elision is best characterized as gestural overlap have been restricted to very few sequence types. In this study, 28 different [#CəC-] sequences are examined to define appropriate acoustic criteria for ‘elision’, to establish whether elision is a deletion process or the endpoint of a continuum of increasing overlap, and to discover whether elision rates vary for individual speakers. Results suggest that the acoustic patterns for elision are consistent with an overlap account. Individual speakers differ as to whether they increase elision

Addressing phonological questions with ultrasound.

Ultrasound can be used to address unresolved questions in phonological theory. To date, some studies have shown that results from ultrasound imaging can shed light on how differences in phonological elements are implemented. Phenomena that have been investigated include transitional schwa, vowel coalescence, and transparent vowels. A study of consonant cluster phonotactics is presented as an example of how ultrasound methodology can be used to examine phonological issues. Five English speakers presented with phonotactically illegal non‐words (e.g., /zgomu/) typically repaired these sequences with vowel insertion (e.g., [z▒gomu]). Using ultrasound imaging, the production of these words is compared to legal sequences that are articulatorily similar, such as succumb and scum to assess the nature of the schwa found between /z/ and the following consonant. Results indicate that for some speakers, production of schwa in /zC/ sequences is not consistent with the phonological epenthesis of a schwa. Instead, speakers appear to be failing to sufficiently overlap the consonant gestures.

Phonetic bases of similarities in cross-language production: Evidence from English and Catalan

Abstract Previous research has shown that speakers do not produce all non-native phonotactic sequences with equal accuracy. Several reasons for these accuracy differences have been proposed, including markedness, analogical extension from permitted sequences, and language-independent phonetic factors. In this study, evidence from the production of unattested obstruent-initial onset clusters by English and Catalan speakers tests the viability of these explanations. Variables manipulated in this study include the manner, place, and voicing of the consonant clusters, and the input modality of the stimuli—whether speakers were presented the stimuli in an audio+text condition, or in an audio-only condition. Results demonstrate none of the linguistic factors interacted with language background; all speakers were less accurate on stop-initial sequences than fricative-initial ones, and on voiced sequences than voiceless sequences. It is argued that the fact that the particular accuracy patterns are independent of language background is incompatible with an analogy-based explanation, and is better accounted for by language-independent phonetic factors. However, the role of the native language phonology is reflected in the preferred repair types, which vary by native language. Finally, while the presence of text improves performance, the patterns of accuracy are still largely the same for both audio+text and audio-only input, suggesting that the underlying mechanisms responsible for speech production are independent of input modality.

The relationship between the perception of non-native phonotactics and loanword adaptation

This study examines how phonetic details produced by non-bilingual borrowers (‘disseminators ’) are categorised when new words are transmitted to the monolinguals of the borrowing language community (‘recipients’). The stimuli are based on research showing that the schwa inserted by English speakers into non-native clusters (e.g. /zgAmo/£[z@gAmo]) differs acoustically from lexical schwa (e.g. [z@gAmo]). In Experiment 1, listeners transcribed Cluster (CC), Lexical (C@C) and Transitional (C@C) stimuli produced by an English speaker. Transcriptions of C@C stimuli were split between CC and CVC, and participants wrote C@C with a vowel less often than they did C@C. Experiment 2 demonstrated that listeners had difficulty discriminating between C@C and both CC and C@C. These findings suggest that C@C is acoustically intermediate between clusters and schwas; thus recipients may assign C@C token to either of the phonotactic categories CC or C@C. The ramifications of these findings for loanwords and the acquisition of phonological contrast are discussed.

Phonotactics and articulatory coordination interact in phonology: evidence from nonnative production.

A core area of phonology is the study of phonotactics, or how sounds are linearly combined. Recent cross-linguistic analyses have shown that the phonology determines not only phonotactics but also the articulatory coordination or timing of adjacent sounds. In this article, I explore how the relation between coordination and phonotactics affects speakers producing nonnative sequences. Recent experimental results (Davidson 2005, 2006) have shown that English speakers often repair unattested word-initial sequences (e.g., /zg/, /vz/) by producing the consonants with a less overlapping coordination. A theoretical account of the experimental results employs Gafoss (2002) constraint-based grammar of coordination. In addition to Gafoss Alignment constraints establishing temporal relations between consonants, a family of Release constraints is proposed to encode phonotactic restrictions. The interaction of Alignment and Release constraints accounts for why speakers produce nonnative sequences by failing to adequately overlap the articulation of the consonants. The optimality theoretic analysis also incorporates floating constraints to explain why speakers are not equally accurate on all unattested clusters.

Sources of illusion in consonant cluster perception

Abstract Previous studies have shown that listeners have difficulty discriminating between non-native CC sequences and licit alternatives (e.g. Japanese [ebzo]-[ebuzo], English [bnif]-[bənif]) ( Berent et al., 2007 , Dupoux et al., 1999 ). Some have argued that the difficulty in distinguishing these illicit–licit pairs is due to a “perceptual illusion” caused by the phonological system, which prevents listeners from accurately perceiving a phonotactically unattested consonant cluster. In this study, we explore this and other sources of perceptual illusion by presenting English listeners with non-native word-initial clusters paired with various modifications, including epenthesis, deletion, C1 change, and prothesis, in both AX and ABX discrimination tasks (e.g. [zmatu]-[zəmatu], [matu], [smatu], or [əzmatu]). For English listeners, fricative–initial sequences are most often confused with prothesis, stop–nasal sequences with deletion or change of the first consonant, and stop–stop sequences with vowel insertion. The pattern of results across tasks indicates that in addition to interference from the phonological system, sources of perceptual illusion include language-specific phonetic knowledge, the acoustic similarity of the stimulus items, the task itself, and the number of modifications to illicit sequences used in the experiment.

Phonetic and Phonological Factors in the Second Language Production of Phonemes and Phonotactics

The study of second language (L2) speech production has been informed by research in a number of areas, including phonological theory, acoustic phonetics, and articulatory phonetics. A synthesis of the research in these areas is presented in this paper. First, early theories about ‘foreign accents’ that have continued to influence current research are discussed, including the Contrastive Analysis Hypothesis and interlanguage. Next, we turn to the acquisition of consonants and vowels, which has been the subject of both experimental and theoretical investigations. The last section examines the acquisition of suprasegmental structure, such as syllables, phonotactics, and prosodic position. Several theories that elucidate the relative contributions of first language transfer and universal markedness are presented, such as the Markedness Differential Hypothesis and Optimality Theory. Both phonetic and phonological aspects of L2 production are considered in light of data from learners at all stages of language acquisition, from cross-language speech production studies which may reflect the initial state of language learning to proficient L2 speakers.

Variability in the implementation of voicing in American English obstruents

Abstract Previous research has shown that in languages like English, the implementation of voicing in voiced obstruents is affected by linguistic factors such as utterance position, stress, and the adjacent sound. The goal of the current study is to extend previous findings in two ways: (1) investigate the production of voicing in connected read speech instead of in isolation/carrier sentences, and (2) understand the implementation of partial voicing by examining where in the constriction voicing appears or dies out. The current study examines the voicing of stops and fricatives in the connected read speech of 37 speakers. Results confirm that phrase position, word position, lexical stress, and the manner and voicing of the adjacent sound condition the prevalence of voicing, but they have different effects on stops and fricatives. The analysis of where voicing is realized in the constriction interval shows that bleed from a preceding sonorant is common, but voicing beginning partway through the constriction interval (i.e., negative voice onset time) is much rarer. The acoustic, articulatory, and aerodynamic sources of the patterns of phonation found in connected speech are discussed.