Georgia Zellou

Nasal coarticulation changes over time in Philadelphia English

This study examines change over time in coarticulatory vowel nasality in both real and apparent time in Philadelphia English. We measure nasal-adjacent vowels in words from a corpus of conversational speech and find systematic, community-level changes in degree of nasal coarticulation over time in Philadelphia. Specifically, in all speakers who were under the age of 25 when interviewed, there is an overall trend of increasing nasality in people born between 1950 and 1965, yet people born after 1965 move towards less nasality than speakers born earlier; finally, those born after 1980 reverse this change, moving again toward greater nasal coarticulation. This finding adds nasality to the set of phonetic dimensions that are demonstrably susceptible to diachronic change in a speech community. The observation that the degree of nasal coarticulation changes towards increased coarticulation at one time period and decreased coarticulation at a different time period adds to the growing body of evidence that subphonemic variation is not universally determined, suggesting instead that it is learned and encoded. Furthermore, the changes in nasality are independent from an observed frequency effect. These empirical patterns suggest that language-internal factors, such as lexical frequency, are independent from language external factors, such as community-level phonetic change over time.

Imitability of contextual vowel nasalization and interactions with lexical neighborhood density

This study investigates the imitability of contextual vowel nasalization in English. Unlike other phonetic features reported to be imitable [e.g., vowel formants (Babel, 2012), VOT (Nielsen, 2011)], vowel nasality is non-contrastive in English. Nasality is, however, systematically variable: words from dense lexical neighborhoods (high-ND words) are produced with greater nasality than words from sparse neighborhoods [Scarborough (2004), (2012)]. Two experiments were conducted to test (1) whether (experimentally manipulated) nasality can be imitated in a shadowing task, and (2) whether direction of manipulation (more or less nasality, enhancing or countering natural neighborhood-conditioned patterns) affects shadowing behavior. Subjects shadowed 16 high-ND words (which are naturally more nasal) containing a vowel-nasal sequence and modified by spectral mixing to exhibit either greater-than-natural (experiment 1) or less-than-natural (experiment 2) nasality. Both the increase and the decrease in nasality were imitated (though not overall degree of nasality, as our imitation model was more nasal in both conditions than any of our subjects). This change persisted into a post-shadowing task for just the less-nasal condition. These results indicate that speakers are sensitive to non-contrastive phonetic detail in nasality, affecting their subsequent production. Further, the naturalness of nasality (reflecting neighborhood-conditioned variation) may affect the pattern of imitation.

Phonetic imitation of coarticulatory vowel nasalization

This study investigates the spontaneous phonetic imitation of coarticulatory vowel nasalization. Speakers produced monosyllabic words with a vowel-nasal sequence either from dense or sparse phonological neighborhoods in shadowing and word-naming tasks. During shadowing, they were exposed to target words that were modified to have either an artificially increased or decreased degree of coarticulatory vowel nasality. Increased nasality, which is communicatively more facilitative in that it provides robust predictive information about the upcoming nasal segment, was imitated more strongly during shadowing than decreased nasality. An effect of neighborhood density was also observed only in the increased nasality condition, where high neighborhood density words were imitated more robustly in early shadowing repetition. An effect of exposure to decreased nasality was observed during post-shadowing word-naming only. The observed imitation of coarticulatory nasality provides evidence that speakers and listeners are sensitive to the details of coarticulatory realization, and that imitation need not be mediated by abstract phonological representations. Neither a communicative account nor a representational account could single-handedly predict these observed patterns of imitation. As such, it is argued that these findings support both communicative and representational accounts of phonetic imitation.

Imitation of coarticulatory vowel nasality across words and time

ABSTRACT We investigated phonetic imitation of coarticulatory vowel nasality using an adapted shadowing paradigm in which participants produced a printed word (target) after hearing a different word (prime). Two versions of primes with nasal codas were used: primes with a natural degree of vowel nasality and hypernasalised primes. The version of the prime participants heard varied, whether consistent with their past experience with nasality from the talker or inconsistent, as well as the duration of delay between prime and target. People spontaneously modify coarticulatory nasality to resemble that demonstrated in the prime they were exposed to. Furthermore, this imitation also reflects the degree of nasality demonstrated by overall experience with the speaker’s vowels. The influence of past experience on imitation increases with increased delay between prime and target. Imitation of another speaker appears to involve tracking general articulatory properties about the speaker, and not solely what was specific to the most recent experience.

Individual differences in the production of nasal coarticulation and perceptual compensation

Abstract The current study investigates correlations between individual differences in the production of nasal coarticulation and patterns of perceptual compensation in American English. A production study (Experiment 1) assessed participants’ nasal coarticulation repertoires by eliciting productions of CVC, CVN and NVN words. Stimuli for two perception tasks were created by cross-splicing oral vowels (from C_C words), nasal vowels (from C_N words), and hypernasal vowels (from N_N words) into C_C, C_N, and N_N consonant contexts. Stimuli pairs were presented to listeners in a paired discrimination task (Experiment 2), where similarity of vowels was assessed, and a nasality ratings task (Experiment 3), where relative nasalization of vowels was judged. In the discrimination task, individual differences in produced nasal coarticulation predicted patterns of veridical acoustic perception. Individuals who produce less extensive anticipatory nasal coarticulation exhibit more veridical acoustic perception (indicating less compensation for coarticulation) than individuals who produce greater coarticulatory nasality. However, in the ratings task, listeners’ produced nasal coarticulation did not predict perceptual patterns. Rather, more veridical perceptual response patterns were observed across participants in context-inappropriate coarticulatory conditions, i.e., for hypernasal vowels in C_N contexts (e.g. ben) and nasal vowels in N_N contexts (e.g. mẽn). The results of this study suggest a complex and multifaceted relationship between representations used to produce and perceive speech.

Lexically conditioned phonetic variation in motherese: age-of-acquisition and other word-specific factors in infant- and adult-directed speech

Abstract Words produced to infants exhibit phonetic modifications relative to speech to adult interlocutors, such as longer, more canonical segments and prosodic enhancement. Meanwhile, within speech directed towards adults, phonetic variation is conditioned by word properties: lower word frequency and higher phonological neighborhood density (ND) correlate with increased hyperarticulation and degree of coarticulation. Both of these types of findings have interpretations that recruit listener-directed motivations, suggesting that talkers modify their speech in an effort to enhance the perceptibility of the speech signal. In that vein, the present study examines lexically-conditioned variation in infant-directed speech. Specifically, we predict that the adult-reported age at which a word was learned – lexical age-of-acquisition (AoA) – conditions phonetic variation in infant-directed speech. This prediction is indeed borne out in spontaneous infant-directed speech: later-acquired words are produced with more hyperarticulated vowels and a greater degree of nasal coarticulation. Meanwhile, ND predicts phonetic variation in data from spontaneous adult-directed speech, while AoA does not independently influence production. The patterns of findings in the current study support the stance that evaluation of the need for clarity is tuned to the listener. Lexical difficulty is evaluated by AoA in infant-directed speech, while ND is most relevant in adult-directed speech.

Phonetic and phonological patterns of nasality in Lakota vowels

Lakota (Siouan) has both contrastive and coarticulatory vowel nasality, and both nasal and oral vowels can occur before or after a nasal consonant. This study examines the timing and degree patterns of acoustic vowel nasality across contrastive and coarticulatory contexts in Lakota, based on data from six Lakota native speakers. There is clear evidence of both anticipatory and carryover nasal coarticulation across oral and nasal vowels, with a greater degree of carryover than anticipatory nasalization. Nasality in carryover contexts is nonetheless restricted: the oral–nasal contrast is neutralized for high back vowels in this context and realized for three of the six speakers in low vowels. In the absence of nasal consonant context, contrastive vowel nasalization is generally greatest late in the vowel. Low nasal vowels in carryover contexts parallel this pattern (despite the location of the nasal consonant before the vowel), and low nasal vowels in anticipatory contexts are most nasal at the start of the vowel. We relate the synchronic patterns of coarticulation in Lakota to both its system of contrast and diachronic processes in the evolution of nasality in Lakota. These data reflect that coarticulatory patterns, as well as contrastive patterns, are grammatical and controlled by speakers.

Use of waveform mixing to synthesize a continuum of vowel nasality in natural speech

Studies of the perception of vowel nasality often use synthesized stimuli to produce controlled gradience in nasality. To investigate the perception of nasality in natural speech, a method was developed wherein vowels differing naturally in nasality (e.g., from CVC and NVN words) are mixed to yield tokens with various degrees of nasality. First, monosyllables (e.g., CVC, NVC, CVN, NVN) matched for vowel quality and consonant place of articulation were recorded. The vowels from two tokens were excised, matched for amplitude, duration and pitch contour, and then overlaid sample-by-sample according to a specified ratio. The resulting vowel was spliced back into the desired consonantal context. Iterating this process over a series of ratios produced natural-sounding tokens along a continuum of vowel nasality. Acoustic measurements of the nasality of output tokens [using A1-P0 (Chen, 1997)] confirmed a relation between the ratio used and the nasality of the output. Stimuli created in this manner were used in a...

Interaction of memory and specificity in auditory repetition priming

This study examines the influences of abstract and episodic representations of words in auditory repetition priming. Two manipulations of prime and target items were employed, token-change and voice-change. First, either the target item consisted of a different token spoken by the same speaker as the prime (token-change), or the target item was a token spoken by a different speaker/different gender (voice-change) than the prime. Second, lapse between prime and target varied across three conditions: no-lapse (no intervening trials between prime and target), medium-lapse (exactly ten intervening trials), and long-lapse (exactly 20 intervening trials). Stimuli were presented using an auditory lexical decision task (with an equal number of English-like nonwords). The reaction time data reveal the greatest facilitation between token-change no-lapse prime-target pairs (256 ms), followed by voice-change no-lapse pairs (182 ms). Facilitation effects were comparable across both the medium-lapse and long-lapse cond...

Specificity for coarticulatory vowel nasality in lexical representations

Surface-level phonetic details are used during word recognition. Yet, questions remain about how these details are encoded in lexical representations and the role of memory and attention during this process. The current study utilizes lexical repetition priming to examine the effect of a delay between hearing a word repeated with either the same or different coarticulatory patterns on lexical recognition. Listeners were faster to recognize repeated words with the same patterns of coarticulatory nasality, confirming that subphonemic information is encoded in the lexicon. Furthermore, when listeners had to adapt to more than one talker, greater coarticulatory specificity in delayed priming was observed suggesting that word-specific encoding of subphonemic details is an active cognitive process.