Perception of dynamic information for vowels in syllable onsets and offsets

It has been demonstrated using the “silent-center” (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets,taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsetsalone or syllable offsetsalone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable off-sets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as “front” or “back” was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

汉语语句重音的分类和分布

通过两个独立进行的重音标注实验对汉语语句重音的分类和分布进行了初步探讨。实验l是由60位普通被试参加的音节重音突显度的知觉实验。实验2是由本文三位作者参加的重音类别标注实验,在此实验中语句重音被划分为节奏重音和语义重音。实验2中对于语句重音的分类性标注结果得到了实验l中普通被试对音节重音突显度知觉结果的支持,这说明人们确实能够感知到两种不同类型的重音。实验结果还表明,节奏重音倾向于出现在较大韵律单元内的最末韵律词的末音节上,并且与适当的停延相伴生,语义重音的分布则与语句的韵律结构的关系不大。     

The use of rhythm in attending to speech

Three experiments examined attentional allocation during speech processing to determine whether listeners capitalize on the rhythmic nature of speech and attend more closely to stressed than to unstressed syllables. Ss performed a phoneme monitoring task in which the target phoneme occurred on a syllable that was either predicted to be stressed or unstressed by the context preceding the target word. Stimuli were digitally edited to eliminate the local acoustic correlates of stress. A sentential context and a context composed of word lists, in which all the words had the same stress pattern, were used. In both cases, the results suggest that attention may be preferentially allocated to stressed syllables during speech processing. However, a normal sentence context may not provide strong predictive cues to lexical stress, limiting the use of the attentional focus.     

Spectral fissioning in phonemic transformations

Listeners presented with a repeated sequence of brief (30- to 100-msec) steady-state vowels hearphonemic transformations—they cannot identify the vowels, but they perceive two simultaneous utterances that differ in both phonemic content and timbre (Warren, Bashford, & Gardner, 1990). These utterances consist of either English words or syllables that occur in English words. In the present study, we attempted to determine whether the two percepts represent alternative interpretations of the same formant structures, or whether different portions of the vowels are used for each verbal organization. It was found that separate spectral regions are employed for each verbal form; Components below 1500 Hz were generally used for one form, and components above 1500 Hz for the other. Hypotheses are offered concerning the processes responsible for the verbal organization of the vowel sequences and for the splitting into two spectrally limited forms. It appears that the tendency to organize spectral regions separately competes with, and can overcome, the tendency to integrate the different spectral components of speech into a single auditory image. A contralateral induction paradigm was used in a procedure designed to quantitatively evaluate these opposing forces of spectral fission and fusion.     

Dependence of 'audio-phonatoric coupling' of speech rate and speech loudness]

The 'audio-phonatoric coupling' (APC) was investigated in two independent experiments. Slightly delayed auditory feedback (delay time 40 ms) of the subjects' own speech was used as experimental method. The first experiment was conducted to examine whether the strength of the APC depends on the speech rate. In this experiment 16 male Subjects (Ss) were required to utter the testword/tatatas/either with stress placing on the first or second syllable at two different speech rates (fast and slow). In 16% of the randomly chosen speech trials, the delayed auditory feedback (DAF; 40 ms delay) was introduced. It could be shown that the stressed phonation was significantly lengthened under the DAF condition. This lengthening was greater when Ss spoke slowly. The unstressed phonations were not influenced by the DAF condition. The second experiment was conducted to examine whether or not speech intensity effects APC. Nine male Ss were required to utter the testword/tatatas/either with stress placing on the first or second syllable using three different speech intensities (30 dB, 50 dB and 70 dB). In 16% of the randomly chosen speech trials DAF condition was introduced. It could be shown that speech intensity does not influence the DAF effect (lengthening of stressed phonation). These findings were taken as evidence that the auditory feedback of the subjects' own speech can be incorporated into speech control during ongoing speech. Obviously, this feedback information is efficient only during the production of stressed syllables, and varies as a function of speech rate. In addition, the significance of stressed syllables for the structuring of speech is discussed.     

Perception of a phonetic contrast in multisyllabic utterances by 2-month-old infants

In the present study, three aspects of the 2-month-old’s perception of multisyllabic utterances were explored. First, do infants perceive phonetic contrasts occurring either in the initial (Bada-Gada) or medial (Daba-Daga) positions of multisyllabic utterances? Second, are infants more likely to perceive these contrasts in stressed as opposed to unstressed syllables? Third, will infants detect a difference between two stress patterns? Our results indicate the following: (1) Two-month-olds are sensitive to place-of-articulation differences occurring in either the initial or medial positions of multisyllabic stimuli. (2) Whether the contrast occurred between stressed or unstressed syllables had little or no effect on the infant’s ability to detect it. (3) Infants as young as 2-months old respond to differences between stress patterns.     

Perception of dynamic information for vowels in syllable onsets and offsets.

It has been demonstrated using the "silent-center" (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets, taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsets alone or syllable offsets alone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable offsets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as "front" or "back" was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

Support for context effects on segmentation and segments depends on the context

Listeners must adapt to differences in speech rate across talkers and situations. Speech rate adaptation effects are strong for adjacent syllables (i.e., proximal syllables). For studies that have assessed adaptation effects on speech rate information more than one syllable removed from a point of ambiguity in speech (i.e., distal syllables), the difference in strength between different types of ambiguity is stark. Studies of word segmentation have shown large shifts in perception as a result of distal rate manipulations, while studies of segmental perception have shown only weak, or even nonexistent, effects. However, no study has standardized methods and materials to study context effects for both types of ambiguity simultaneously. Here, a set of sentences was created that differed as minimally as possible except for whether the sentences were ambiguous to the voicing of a consonant or ambiguous to the location of a word boundary. The sentences were then rate-modified to slow down the distal context speech rate to various extents, dependent on three different definitions of distal context that were adapted from previous experiments, along with a manipulation of proximal context to assess whether proximal effects were comparable across ambiguity types. The results indicate that the definition of distal influenced the extent of distal rate effects strongly for both segments and segmentation. They also establish the presence of distal rate effects on word-final segments for the first time. These results were replicated, with some caveats regarding the perception of individual segments, in an Internet-based sample recruited from Mechanical Turk.     

Influences of rate, length, and complexity on speech disfluency in a single-speech sample in preschool children who stutter

The purpose of the present study was (1) to determine whether speech rate, utterance length, and grammatical complexity (number of clauses and clausal constituents per utterance) influenced stuttering-like disfluencies as children became more disfluent at the end of a 1200-syllable speech sample [Sawyer, J., & Yairi, E. (2006). The effect of sample size on the assessment of stuttering severity. American Journal of Speech-Language Pathology, 15, 36-44] and (2) to explore the interaction of speech rate, length, and grammatical complexity at the beginning (syllables 1-300, Section A) and the end (syllables 901-1200, Section B) of the speech sample. Participants were eight boys and six girls (M=40.9 months) who were selected from the Sawyer and Yairi [Sawyer, J., & Yairi, E. (2006). The effect of sample size on the assessment of stuttering severity. American Journal of Speech-Language Pathology, 15, 36-44] study. Mean length of utterance (MLU) in morphemes, the number of clauses, clausal constituents, and articulation rate, measured in syllables per second were analyzed from the children's conversational speech. The median split procedure [Logan, K., & Conture, E. (1995). Length, grammatical complexity, and rate differences in stuttered and fluent conversational utterances of children who stutter. Journal of Fluency Disorders, 20, 35-61; Yaruss, J. S. (1997). Utterance timing and childhood stuttering. Journal of Fluency Disorders, 22, 263-286] was used to study interactions between articulation rate, utterance length, and grammatical complexity across the two sections. The mean number of clauses per utterance, clausal constituents per utterance, and articulation rate revealed no significant differences between Section A and Section B, whereas MLU significantly increased in Section B (p=.013). Clausal constituents and MLU were significantly correlated both in Sections A and B. The median split procedure revealed trends for utterances characterized as high length and low-speech rate to be greater in number in Section B than A, but the differences were not significant. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to: (a) describe the influence of grammatical complexity and mean length of utterance on disfluent speech; (b) compare different procedures for assessing speech rate and determine why the effects of articulation rate have been inconclusive; (c) discuss procedures for comparing length, rate, and complexity across a single-speech sample; and (d) explain why therapeutic methods that emphasize shorter utterance lengths, rather than only slower speech rates, are advisable in establishing fluency in preschool children who stutter.     

Perceptuomotor adaptation to a speech feature

Selective adaptation experiments were conducted to test for the presence of a mechanism that mediates an aspect of both speech perception and speech production. Ss were instructed to utter /i/ or /bi/ after listening to repetitions of either of these syllables or to repetitions of the vowel /i/. Analysis of the utterances showed that a timing relation which distinguishes /pi/from /bi/, namely the latency in onset of voicing relative to the release burst of the consonant, varied systematically for the /pi/ utterances but not for the /bi/ utterances as a function of the speech input. The effect for the /pi/ utterances was shown not to be attributable to factors such as compensation for distorted perception of the /pi/ adapting stimulus or voluntary mimicry of this stimulus.     

Linguistic stress, within-word position, and grammatical class in relation to early childhood stuttering

The purpose of the present study was to investigate whether the link that has been established between stuttering and linguistic stress in adolescents and adults (the so-called stress effect) can also be observed in childhood stuttering. To account for confounding variables, both within-word position and grammatical class were measured, because these factors covary with linguistic stress. Speech samples of 22 preschool children (mean time of 9 months since onset of stuttering) were analyzed. The relative stress of each syllable was rated and syllables were categorized into long and short stressed, unstressed, and intermediately stressed syllables. Results showed that 97.8% of stuttering events occurred on first syllables of words and 76.5% on the first sound of syllables, that means a clear word-initial effect. Stuttering frequency on first syllables of function words was 16.9% and significantly higher than the frequency of stuttered first syllables of content words (11.5%). In function words short stressed syllables and intermediately stressed syllables were stuttered more often than unstressed syllables. The analysis for individual disfluency types revealed that, for function words, stuttering on short stressed syllables was associated with prolongations and syllable repetitions. However, in intermediately stressed syllables stuttering coincided most often with one-syllable word repetitions. This differentiation of the stress effect may suggest different causal mechanisms underlying these disfluency types. Educational objectives: The reader will learn about and be able to: (1) describe how within-word position, grammatical class, and linguistic stress effect stuttering frequency in preschool children who stutter; (2) explain how the occurrence of individual disfluency types depends on linguistic stress; (3) discuss how patterns of adults and preschool children who stutter differ in regard to these aspects.     

Untrained speakers' use of prosody in syntactic disambiguation and listeners' interpretations

We investigated how naively produced prosody affects listeners' end interpretations of ambiguous utterances. Non-professional speakers who were unaware of any ambiguity produced ambiguous sentences couched in short, unambiguous passages. In a forced-choice task, listeners could not tell which context the isolated ambiguous sentences came from (Exp. 1). However, listeners were able to correctly paraphrase the least ambiguous subset of these utterances, showing that prosody can be used to resolve ambiguity (Exp. 2). Nonetheless, in everyday language use, both prosody and context are available to interpret speech. When the least ambiguous sentences were cross-spliced into contexts biasing towards their original interpretations or into contexts biasing towards their alternative interpretations, answers to content questions about the ambiguous sentence, confidence ratings, and ratings of naturalness all indicated that prosody is ignored when context is available (Exp. 3). Although listeners can use prosody to interpret ambiguous sentences, they generally do not, and this makes sense in light of the frequent lack of reliable prosodic cues in everyday speech. Received: 3 April 1998 / Accepted: 21 October 1998     

The relative accessibility of phonemes and syllables

Previous research comparing detection times for syllables and for phonemes has consistently found that syllables are responded to faster than phonemes. This finding poses theoretical problems for strictly hierarchical models of speech recognition, in which smaller units should be able to be identified faster than larger units. However, inspection of the characteristics of previous experiments’ stimuli reveals that subjects have been able to respond to syllables on the basis of only a partial analysis of the stimulus. In the present experiment, five groups of subjects listened to identical stimulus material. Phoneme and syllable monitoring under standard conditions was compared with monitoring under conditions in which near matches of target and stimulus occurred on no-response trials. In the latter case, when subjects were forced to analyze each stimulus fully, phonemes were detected faster than syllables.     

Attentional engagement during syllable discrimination: The role of salient prosodic cues in 6- to 8-month-old infants

Prosodic cues drive speech segmentation and guide syllable discrimination. However, less is known about the attentional mechanisms underlying an infant's ability to benefit from prosodic cues. This study investigated how 6- to 8-month-old Italian infants allocate their attention to strong vs. weak syllables after familiarization with four repeats of a single CV sequence with alternating strong and weak syllables (different syllables on each trial). In the discrimination test-phase, either the strong or the weak syllable was replaced by a pure tone matching the suprasegmental characteristics of the segmental syllable, i.e., duration, loudness and pitch, whereas the familiarized stimulus was presented as a control. By using an eye-tracker, attention deployment (fixation times) and cognitive resource allocation (pupil dilation) were measured under conditions of high and low saliency that corresponded to the strong and weak syllabic changes, respectively. Italian learning infants were found to look longer and also to show, through pupil dilation, more attention to changes in strong syllable replacement rather than weak syllable replacement, compared to the control condition. These data offer insights into the strategies used by infants to deploy their attention towards segmental units guided by salient prosodic cues, like the stress pattern of syllables, during speech segmentation.     

The role of phonemes and syllables in the perceived similarity of speech sounds for children

In two experiments, we investigated the factors that influence the perceived similarity of speech sounds at two developmental levels. Kindergartners and second graders were asked to classify nonsense words, which were related by syllable and phoneme correspondences. The results support the existence of a developmental trend toward increased attention to individual phonemic segments. Moreover, one significant factor in determining the perceived similarity of speech sounds appears to be the position of the component correspondences; attention to the beginning of utterances may have developmental priority. An unexpected finding was that the linguistic status of the unit involved in a correspondence (whether it was a syllable or a phoneme) did not seem particularly important. Apparently, the factors which contribute to the perceived similarity of speech sounds in the classification task are not identical to those which underlie performance in explicit segmentation and manipulation tasks, since in the latter sort of task, syllables are more accessible than phonemes for young children. The present task may tap a level of processing that is closer to the one entailed in word recognition and lexical access.     

Look who's talking: speech style and social context in language input to infants are linked to concurrent and future speech development

Language input is necessary for language learning, yet little is known about whether, in natural environments, the speech style and social context of language input to children impacts language development. In the present study we investigated the relationship between language input and language development, examining both the style of parental speech, comparing ‘parentese’ speech to standard speech, and the social context in which speech is directed to children, comparing one‐on‐one (1:1) to group social interactions. Importantly, the language input variables were assessed at home using digital first‐person perspective recordings of the infants' auditory environment as they went about their daily lives (N =26, 11‐ and 14‐months‐old). We measured language development using (a) concurrent speech utterances, and (b) word production at 24 months. Parentese speech in 1:1 contexts is positively correlated with both concurrent speech and later word production. Mediation analyses further show that the effect of parentese speech‐1:1 on infants' later language is mediated by concurrent speech. Our results suggest that both the social context and the style of speech in language addressed to children are strongly linked to a child's future language development.     

Tracking the speech signal – Time-locked MEG signals during perception of ultra-fast and moderately fast speech in blind and in sighted listeners

Blind people can learn to understand speech at ultra-high syllable rates (ca. 20 syllables/s), a capability associated with hemodynamic activation of the central-visual system. To further elucidate the neural mechanisms underlying this skill, magnetoencephalographic (MEG) measurements during listening to sentence utterances were cross-correlated with time courses derived from the speech signal (envelope, syllable onsets and pitch periodicity) to capture phase-locked MEG components (14 blind, 12 sighted subjects; speech rate = 8 or 16 syllables/s, pre-defined source regions: auditory and visual cortex, inferior frontal gyrus). Blind individuals showed stronger phase locking in auditory cortex than sighted controls, and right-hemisphere visual cortex activity correlated with syllable onsets in case of ultra-fast speech. Furthermore, inferior-frontal MEG components time-locked to pitch periodicity displayed opposite lateralization effects in sighted (towards right hemisphere) and blind subjects (left). Thus, ultra-fast speech comprehension in blind individuals appears associated with changes in early signal-related processing mechanisms both within and outside the central-auditory terrain.     

Statistical clustering and the contents of the infant vocabulary

Infants parse speech into word-sized units according to biases that develop in the first year. One bias, present before the age of 7 months, is to cluster syllables that tend to co-occur. The present computational research demonstrates that this statistical clustering bias could lead to the extraction of speech sequences that are actual words, rather than missegmentations. In English and Dutch, these word-forms exhibit the strong-weak (trochaic) pattern that guides lexical segmentation after 8 months, suggesting that the trochaic parsing bias is learned as a generalization from statistically extracted bisyllables, and not via attention to short utterances or to high-frequency bisyllables. Extracted word-forms come from various syntactic classes, and exhibit distributional characteristics enabling rudimentary sorting of words into syntactic categories. The results highlight the importance of infants' first year in language learning: though they may know the meanings of very few words, infants are well on their way to building a vocabulary.     

Stressed and word-final syllables in infant-directed speech

Comparisons between infant-directed and adult-directed speech were conducted to determine whether word-final syllables are highlighted in infant-directed speech. Samples of adult-directed and infant-directed speech were collected from 8 mothers of 6-month-old and 8 mothers of 9- month-old infants. Mothers were asked to label seven objects both to an experimenter and to their infant. Duration, pitch, and amplitude were measured for whole words and for each of the target word syllables. As in prior research, the infant-directed targets were higher pitched and longer than adult-directed targets. The results also extend beyond previous results in showing that lengthening of final syllables in infant-directed speech is particularly exaggerated. Results of analyses comparing word-final versus nonfinal unstressed syllables in utterance-medial position in infant-directed speech showed that lengthening of unstressed word-final syllables occurs even in utterance-internal positions. These results could suggest a mechanism for proposals that word-final syllables are perceptually salient to young children.     

Effects of auditory masking by white noise on primary stressing during spontaneous speech

6 adult subjects (3 men, 3 women) produced highly similar spontaneous speech utterances in quiet and with 90-dB SPL white noise. The frequency of occurrence of perceptual judgments of primary stressing in an utterance was not affected by the masking noise. This finding supplements our previous report that variability for stress production of fundamental frequency (fo) during spontaneous speech was preserved under short-term auditory disruption. Also, it adds further support to the contention that fo is under open-loop regulation.