Convergence to shortened and lengthened voice onset time in an imitation task.

Convergence to variation in voice onset time (VOT) of English voiceless stops is reported to be selective, with speakers adjusting their VOTs after exposure to stimuli with lengthened, but not shortened, VOT. The current study re-examined this proposed selectivity with an explicit imitation paradigm designed to maximize convergence, using stimuli with more extreme differences, and explored the perceptual salience of the differences in a discrimination task. Participants showed phonetic convergence to both shortened and lengthened VOT, and better discrimination of shortened than lengthened VOT. Results suggest that there is no general constraint against convergence to shortened VOT.

Voice Onset Time Imitation in Teens Versus Adults.

PURPOSE: We compare teens' and adults' imitation of sentences with shortened and lengthened voice onset time (VOT), in order to test whether purported age-based advantages in phonetic acquisition may be due to differences in imitative ability. METHOD: Teens (M age = 13, n = 39) and adults (n = 31) completed an explicit imitation and discrimination task on pairs of sentences characterized by canonical and manipulated (shortened or lengthened) VOT. We assessed extent of imitation using two acoustic metrics (ΔVOT and Proximity), accuracy on the discrimination task, and correlations between imitation and perception. RESULTS: Both age groups modified VOT when imitating stimuli with both lengthened and shortened VOT. Adults, however, showed significantly more lengthening than teens (i.e., higher ΔVOT), as well as VOT values that were slightly but significantly closer to the target stimulus values (i.e., lower proximity). Both age groups showed above-chance discrimination accuracy, and a significant relationship between individual perception and production performance was found for lengthened-VOT sentences. CONCLUSIONS: We found no evidence that teens have a greater imitative ability than adults; in fact, adults showed significantly more imitation based on both acoustic metrics. Both age groups showed robust imitation of VOT manipulations in both directions, in contrast to previous work showing lack of imitation for shortened VOT. Extent of imitation was predicted by individual perceptual performance, but only to a limited degree, underscoring the importance of other factors in explaining individual variation in imitative ability.

Unified Coding of Spectral and Temporal Phonetic Cues: Electrophysiological Evidence for Abstract Phonological Features.

Spoken word recognition models and phonological theory propose that abstract features play a central role in speech processing. It remains unknown, however, whether auditory cortex encodes linguistic features in a manner beyond the phonetic properties of the speech sounds themselves. We took advantage of the fact that English phonology functionally codes stops and fricatives as voiced or voiceless with two distinct phonetic cues: Fricatives use a spectral cue, whereas stops use a temporal cue. Evidence that these cues can be grouped together would indicate the disjunctive coding of distinct phonetic cues into a functionally defined abstract phonological feature. In English, the voicing feature, which distinguishes the consonants [s] and [t] from [z] and [d], respectively, is hypothesized to be specified only for voiceless consonants (e.g., [s t]). Here, participants listened to syllables in a many-to-one oddball design, while their EEG was recorded. In one block, both voiceless stops and fricatives were the standards. In the other block, both voiced stops and fricatives were the standards. A critical design element was the presence of intercategory variation within the standards. Therefore, a many-to-one relationship, which is necessary to elicit an MMN, existed only if the stop and fricative standards were grouped together. In addition to the ERPs, event-related spectral power was also analyzed. Results showed an MMN effect in the voiceless standards block-an asymmetric MMN-in a time window consistent with processing in auditory cortex, as well as increased prestimulus beta-band oscillatory power to voiceless standards. These findings suggest that (i) there is an auditory memory trace of the standards based on the shared [voiceless] feature, which is only functionally defined; (ii) voiced consonants are underspecified; and (iii) features can serve as a basis for predictive processing. Taken together, these results point toward auditory cortex's ability to functionally code distinct phonetic cues together and suggest that abstract features can be used to parse the continuous acoustic signal.

Sorry, Not Sorry: The independent role of multiple phonetic cues in signaling the difference between two word meanings.

We examine the use of multiple subphonemic differences distinguishing homophones in production and perception, through a case study focusing on the distinction between two polysemous senses of the English word "sorry" (apology vs. attention-seeking). An analysis of production data from voice actors revealed significant and substantial durational differences between the two meanings. Tokens expressing an apology were longer than attention-seeking tokens, and the situational intensity of the context also independently affected duration. When asked to identify the meaning in a two-way forced-choice task after hearing each token spliced out of its context, listeners were above chance (64.7% accuracy) in identifying the intended meaning, and their responses were significantly correlated with the duration, intensity, and intonation contour (but not mean F0) of the productions. In a second perception task, listeners heard tokens of "sorry" that had been systematically manipulated to vary in duration, intensity, and intonation contour, with responses indicating that each of these dimensions played an independent role in listeners' judgments. The results highlight the importance of broadening the scope of research on the use of subphonemic detail during lexical access and considering a wider range of lexical and non-lexical factors that condition variability on multiple acoustic dimensions, in order to work toward a more accurate picture of the systematic variability available in the input and tracked by listeners.

Comparing Phonetic Convergence in Children and Adults.

Observations by sociolinguists suggest that when children relocate to a new community, they rapidly learn to imitate their peers, adopting the new local accent faster and more effectively than adults. However, few well-controlled laboratory experiments have been conducted comparing speech or accent imitation across ages. Here, we investigated Canadian English-speaking children's and adults' imitation of three model speakers: a Canadian English talker, an Australian English talker, and a non-native Mandarin English talker who learned English later in life. The speech of all three talkers was manipulated to have elongated voice onset time (VOT) on word initial stop consonants. The dependent measure was how much participants would lengthen their VOTs after exposure to one of the talkers in two paradigms: delayed shadowing (Experiment 1) and immediate shadowing (Experiment 2). We predicted that overall children would show more imitation than adults, particularly when imitating the Canadian English talker, given previous work on children's social preferences. Although we did not observe age differences in either study, when shadowing was immediate, we found that imitation was influenced by the accent of the speaker, but not in the manner we predicted: both age groups imitated the Mandarin-accented model more strongly than the Canadian model. When shadowing was delayed, we observed no evidence of imitation. We discuss our findings in light of other recent work, and conclude that the development of speech imitation is an area ripe for further investigation.

The Other Accent Effect in Talker Recognition: Now You See It, Now You Don't.

The existence of the Language Familiarity Effect (LFE), where talkers of a familiar language are easier to identify than talkers of an unfamiliar language, is well-documented and uncontroversial. However, a closely related phenomenon known as the Other Accent Effect (OAE), where accented talkers are more difficult to recognize, is less well understood. There are several possible explanations for why the OAE exists, but to date, little data exist to adjudicate differences between them. Here, we begin to address this issue by directly comparing listeners' recognition of talkers who speak in different types of accents, and by examining both the LFE and OAE in the same set of listeners. Specifically, Canadian English listeners were tested on their ability to recognize talkers within four types of voice line-ups: Canadian English talkers, Australian English talkers, Mandarin-accented English talkers, and Mandarin talkers. We predicted that the OAE would be present for talkers of Mandarin-accented English but not for talkers of Australian English-which is precisely what we observed. We also observed a disconnect between listeners' confidence and performance across different types of accents; that is, listeners performed equally poorly with Mandarin and Mandarin-accented talkers, but they were more confident with their performance with the latter group of talkers. The present findings set the stage for further investigation into the nature of the OAE by exploring a range of potential explanations for the effect, and introducing important implications for forensic scientists' evaluation of ear witness testimony.

The development of gendered speech in children: Insights from adult L1 and L2 perceptions.

Past studies have shown that boys and girls sound distinct by 4 years old, long before sexual dimorphisms in vocal anatomy develop. These gender differences are thought to be learned within a particular speech community. However, no study has asked whether listeners' sensitivity to gender in child speech is modulated by language experience. This study shows that gendered speech emerges at 2.5 years old, and that L1 listeners outperform L2 listeners in detecting these differences. The findings highlight the role of language-specific sociolinguistic factors in both speech perception and production, and show that gendered speech emerges earlier than previously suggested.

The independent contribution of voice onset time to perceptual metrics of convergence.

This work explores the relationship between phonetic and perceptual metrics for convergence in shadowed productions by adults and 6-year-old children by isolating the role of voice onset time (VOT) in listeners' similarity judgments. Results show a small but independent role for VOT: listeners were less likely to identify shadowed tokens as more similar to the model when natural VOT convergence present in the stimulus set had been artificially removed (experiments 1 and 2). However, VOT equivalence alone, when accompanied by naturally occurring variation along other dimensions, was not sufficient to drive listeners' judgments of similarity (experiment 3).

Language Specificity in Phonetic Cue Weighting: Monolingual and Bilingual Perception of the Stop Voicing Contrast in English and Spanish.

BACKGROUND/AIMS: This work examines the perception of the stop voicing contrast in Spanish and English along four acoustic dimensions, comparing monolingual and bilingual listeners. Our primary goals are to test the extent to which cue-weighting strategies are language-specific in monolinguals, and whether this language specificity extends to bilingual listeners. METHODS: Participants categorized sounds varying in voice onset time (VOT, the primary cue to the contrast) and three secondary cues: fundamental frequency at vowel onset, first formant (F1) onset frequency, and stop closure duration. Listeners heard acoustically identical target stimuli, within language-specific carrier phrases, in English and Spanish modes. RESULTS: While all listener groups used all cues, monolingual English listeners relied more on F1, and less on closure duration, than monolingual Spanish listeners, indicating language specificity in cue use. Early bilingual listeners used the three secondary cues similarly in English and Spanish, despite showing language-specific VOT boundaries. CONCLUSION: While our findings reinforce previous work demonstrating language-specific phonetic representations in bilinguals in terms of VOT boundary, they suggest that this specificity may not extend straightforwardly to cue-weighting strategies.

Phonetic cue weighting in perception and production.

Speech sound contrasts differ along multiple phonetic dimensions. During speech perception, listeners must decide which cues are relevant, and determine the relative importance of each cue, while also integrating other, signal-external cues. The comparison of cue weighting in perception and production bears on a range of theoretical issues including the processes underlying sound change, the time course of learning, the nature of cues, and the perception-production interface. Research examining the relative alignment of cue weighting across the modalities, on both a community and individual level, has revealed both parallels and asymmetries between the modalities. The extraordinarily wide range of ways that have been used to conceptualize and quantify cue weights reflects the inherent theoretical, methodological, and analytical differences between the two modalities. More consideration of the choices of analytical metrics, explicit discussion of the theoretical assumptions that underlie them, and systematic investigations of different types of cues will lead to more generalizable findings that can be incorporated into computational implementable models of speech processing. This article is categorized under: Linguistics > Language in Mind and Brain Psychology > Language.

The influence of tone language experience and speech style on the use of intonation in language discrimination.

This work tests whether listeners' use of suprasegmental information in speech perception is modulated by language background and speech style. Native Mandarin (tone language) and Malay (non-tone language) listeners completed an AX language discrimination task with four levels of signal degradation and two speech styles. Listeners in both groups showed more benefit from pitch information in read than in spontaneous speech. Mandarin listeners showed a greater benefit than Malay listeners from the inclusion of f0 information in a segmentally degraded signal, suggesting that experience with lexical tone may extend to increased attention and/or sensitivity to phrase-level pitch contours.

The effect of sentential context on phonetic categorization is modulated by talker accent and exposure.

Higher-level factors, including the contextual plausibility of competing word candidates, interact with lower-level phonetic cues to influence how listeners interpret the speech signal. This work shows that listeners' phonetic categorization (e.g., coat versus goat) is more heavily influenced by sentential context when listening to a non-native versus native talker. Further, the effect of context on phonetic categorization decreases as the listener becomes familiar with the talker's phonetic characteristics, for both native and non-native talkers. Overall, results suggest that listeners adjust their perceptual strategies to optimize accurate perception of a talker's message.

Individual differences in perceptual adaptability of foreign sound categories.

Listeners possess a remarkable ability to adapt to acoustic variability in the realization of speech sound categories (e.g., different accents). The current work tests whether non-native listeners adapt their use of acoustic cues in phonetic categorization when they are confronted with changes in the distribution of cues in the input, as native listeners do, and examines to what extent these adaptation patterns are influenced by individual cue-weighting strategies. In line with previous work, native English listeners, who use voice onset time (VOT) as a primary cue to the stop voicing contrast (e.g., 'pa' vs. 'ba'), adjusted their use of f0 (a secondary cue to the contrast) when confronted with a noncanonical "accent" in which the two cues gave conflicting information about category membership. Native Korean listeners' adaptation strategies, while variable, were predictable based on their initial cue weighting strategies. In particular, listeners who used f0 as the primary cue to category membership adjusted their use of VOT (their secondary cue) in response to the noncanonical accent, mirroring the native pattern of "downweighting" a secondary cue. Results suggest that non-native listeners show native-like sensitivity to distributional information in the input and use this information to adjust categorization, just as native listeners do, with the specific trajectory of category adaptation governed by initial cue-weighting strategies.

Individual differences in phonetic cue use in production and perception of a non-native sound contrast.

The current work examines native Korean speakers' perception and production of stop contrasts in their native language (L1, Korean) and second language (L2, English), focusing on three acoustic dimensions that are all used, albeit to different extents, in both languages: voice onset time (VOT), f0 at vowel onset, and closure duration. Participants used all three cues to distinguish the L1 Korean three-way stop distinction in both production and perception. Speakers' productions of the L2 English contrasts were reliably distinguished using both VOT and f0 (even though f0 is only a very weak cue to the English contrast), and, to a lesser extent, closure duration. In contrast to the relative homogeneity of the L2 productions, group patterns on a forced-choice perception task were less clear-cut, due to considerable individual differences in perceptual categorization strategies, with listeners using either primarily VOT duration, primarily f0, or both dimensions equally to distinguish the L2 English contrast. Differences in perception, which were stable across experimental sessions, were not predicted by individual variation in production patterns. This work suggests that reliance on multiple cues in representation of a phonetic contrast can form the basis for distinct individual cue-weighting strategies in phonetic categorization.

Acquisition of the stop-spirant alternation in bilingual Mexican Spanish-English speaking children: theoretical and clinical implications.

The purpose of this study was to identify characteristics of typical acquisition of the Mexican Spanish stop-spirant alternation in bilingual Spanish-English speaking children and to shed light on the theoretical debate over which sound is the underlying form in the stop-spirant allophonic relationship. We predicted that bilingual children would acquire knowledge of this allophonic relationship by the time they reach age 5;0 (years;months) and would demonstrate higher accuracy on the spirants, indicating their role as the underlying phoneme. This quasi-longitudinal study examined children's single word samples in Spanish from ages 2;4-8;2. Samples were phonetically transcribed and analyzed for accuracy, substitution errors and acoustically for intensity ratios. Bilingual children demonstrated overall higher accuracy on the voiced stops as compared to the spirants. Differences in substitution errors across ages were found and acoustic analyses corroborated perceptual findings. The clinical implication of this research is that bilingual children may be in danger of overdiagnosis of speech sound disorders because acquisition of this allophonic rule in bilinguals appears to differ from what has been found in previous studies examining monolingual Spanish speakers.