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PubMed1996

The structural organization of the mental lexicon and its contribution to age-related declines in spoken-word recognition.

Three experiments were conducted within the framework of the Neighborhood Activation Model of spoken-word recognition to study how the structural organization of the mental lexicon may contribute to age-related declines in spoken-language processing. Experiment 1 showed that the number and frequency of words that are phonetically similar to a target word had differential effects on perceptual identification in older and younger adults, with older adults being particularly disadvantaged in identifying hard words (words phonetically similar to many other high-frequency words). Experiment 2 showed that age-related deficits in the ability to identify hard words remained under conditions in which performance for a set of easy words (items phonetically similar to relatively few other low-frequency words) was the same for older and younger adults. In Experiment 3, reducing the resources available for identification by changing from single to multiple talkers reduced word recognition more among older than younger adults. Diminished cognitive resources, impaired inhibitory control, and increased general slowing are discussed as explanations for the results.

Adolescent↗
PubMed2003

Phonological profiles of 2-year-olds with delayed language development: predicting clinical outcomes at age 3.

Twenty-eight 2-year-olds were screened for language development using the Language Development Survey (LDS; L. Rescorla, 1989) and underwent a clinical evaluation within a month following LDS administration. Six measures of phonological development were derived from 20-min language samples of parent-child play interactions, including number of different consonants, number of different consonants in the initial and final positions, number of different consonant clusters in the initial and final position, and percentage of closed syllables shapes. Comparisons were made among 3 groups: (a) those who screened positive on the LDS (LDS+) who were within normal limits on follow-up, (b) those who were identified as language delayed (LD), and (c) children who were language normal (LN). Results revealed that children who were LDS+ and LD had comparable phonetic profiles. The LD group had significantly lower scores on all phonetic measures tested, as compared to the LN group. Clinical recommendations were available on a subset of 13 children who were reassessed at age 3. Children who received "monitor" or "treatment" recommendations at age 3 had significantly lower z scores on measures of phonetic development recorded at 2 years of age than toddlers who received a recommendation of "no concerns" at 3 years. Our preliminary findings indicated that the more delayed the 2-year-old child was in phonological development, the more at risk the child was for continuing delays at age 3.

Child, Preschool↗
PubMed2006

Parametric quantitative acoustic analysis of conversation produced by speakers with dysarthria and healthy speakers.

PURPOSE: This study's main purpose was to (a) identify acoustic signatures of hypokinetic dysarthria (HKD) that are robust to phonetic variation in conversational speech and (b) determine specific characteristics of the variability associated with HKD. METHOD: Twenty healthy control (HC) participants and 20 participants with HKD associated with idiopathic Parkinson's disease (PD) repeated 3 isolated sentences (controlled phonetic content) and 2 min of conversational speech (phonetic content treated as a random variable). A MATLAB-based program automatically calculated measures of contrastivity: speech-pause ratio, intensity variation, median and maximum formant slope, formant range, change in the upper and lower spectral envelope, and range of the spectral envelope. t tests were used to identify which measures were sensitive to HKD and which measures differed by task. Discriminant analysis was used to identify the combination of measures that best predicted HKD, and this analysis was then used as a general measure of contrastivity (Contrastivity Index). Differential effects of HKD on maximum and typical contrastivity levels were tested with interaction of maximum, minimum, and median observations of individual speakers and with pairwise comparisons of skewness and kurtosis of the contrastivity index distributions. RESULTS: Group differences were detected with pairwise comparisons with t tests in 8 of the 9 measures. Percentage pause time and spectral range were identified as the most specific (95%) and accurate (95%) differentiators of HKD and HC conversational speech. Sentence repetition elicited significantly higher levels of contrastivity than conversational speech in both HC and HKD speakers. Maximum and minimum contrastivities were significantly lower in HKD speech, but there was no evidence that HKD affects maximum contrastivity levels more than median contrastivity levels. The HKD speakers' contrastivity distributions were significantly more skewed to lower levels of production. CONCLUSION: HKD can be consistently distinguished from HC speech in both sentence repetition and conversational speech on the basis of intensity variation and spectral range. Although speakers with HKD were effectively able to produce higher contrastivity levels in sentence repetition tasks, they habitually performed closer to the lower end of their production ranges.

Adult↗
PubMed1990

Impairment of speech intelligibility in men with amyotrophic lateral sclerosis.

Speech intelligibility was studied in a group of 25 male patients with amyotrophic lateral sclerosis (ALS). The object of the study was to determine the phonetic impairments underlying the speech intelligibility deficits that frequently accompany ALS. Analyses with a word intelligibility test indicated that the most disrupted phonetic features involved phonatory (voicing contrast) function, velopharyngeal valving, place and manner of articulation for lingual consonants, and regulation of tongue height for vowels. The mean error proportion for the five most severely affected features correlated highly (0.97) with the intelligibility score (percent correct). The phonetic feature analyses are one index of bulbar muscle impairment in amyotrophic lateral sclerosis and also may help to direct the speech management in these individuals.

Adult↗
PubMed1993

Perception of formant transition cues to place of articulation in children with language impairments.

Discrimination and phonetic identification abilities of 5- to 6-year-old children with language impairments were compared to those of 4-year-olds with normally developing language and to previous findings from 5- to 6-year-olds and adults for synthetic stimuli ranging from [ba] to [da]. Results showed similar discrimination sensitivity to the second- and third-formant transition cues of stimuli by all children, with poorest sensitivity by the youngest. Phonetic categorization by children with language impairments was most different from the groups with normal language abilities, evidenced by a difference in the percent of tokens labeled as "BA" and by greater variability in labeling and in placement of phonetic category boundaries. Results support hypotheses by Gathercole and Baddeley (1990) suggesting that the phonological component of working memory may be disordered in children with language impairments. Results are also suggestive of specific difficulties with left-hemisphere processing associated with language learning rather than with problems related to sensitivity to formant transitions of the speech tokens.

Child, Preschool↗
PubMed1995

Acoustic correlates of stress in young children's speech.

This study examined the acoustic correlates of stress in children's productions of familiar words. Previous research has employed experimental words rather than familiar words to examine children's phonetic marking of stress, or has not adequately controlled for phonetic environment. Subjects in this study included 22 children, aged 18-30 months, and 6 adults. Fundamental frequency, duration, and amplitude measures were extracted from stressed and unstressed syllables in two types of comparisons: one that controlled phonetic environment and syllable position (interword) and one that measured the relative effects of stress within the same word (intraword). When the tokens were analyzed on the basis of target stress pattern, results revealed no differences between adults and children in their acoustic marking of stress. Listener judgments showed that approximately 30% of children's two-syllable productions were coded unreliably or were perceived as inaccurately stressed. Overall findings indicate that children control fundamental frequency, amplitude, and duration to derive perceptually identifiable stress contrasts in the majority of their productions but they are not completely adult-like in their marking of stress.

Adult↗
PubMed1996

Perception of voicing cues by children with early otitis media with and without language impairment.

Research on the relationship between early otitis media with effusion (OME), language impairment, and central auditory processing has been equivocal. Identification and discrimination tasks provide us with a sensitive method of assessing speech perception on both an auditory and a phonetic level. The present study examined identification and discrimination of initial bilabial stop consonants differing in voicing by 9-year-old children with a history of severe OME. The groups studied were controlled for language impairment. The ability of these children to perceive major and minor voicing cues was examined using multiple voicing cues. Long-term effects of OME were found for both identification and discrimination performance. Children with OME produced an overall inconsistency in categorization, which suggests poorer phonetic processing. Discrimination was measured by means of "just noticeable differences" (JND). Children with early OME experience demonstrated a greater mean JND than children without early OME experience. Finally, in cases of language impairment with early OME, there was no additional deterioration of auditory or phonetic processing. It appears that either early OME or language impairment can lead to poorer perception.

Adult↗
PubMed1998

Phonological skills of children with specific expressive language impairment (SLI-E): outcome at age 3.

Naturalistic speech samples of 29 3-year-olds diagnosed with specific expressive language delay (SU-E) were compared to those produced by 19 age-matched normally developing peers in order to determine their improvement in phonological skills since age 2, when Rescorla and Ratner (1996) studied them. Specifically, the groups were compared with regard to vocalization rate, verbalizations, fully intelligible utterances, phonetic inventories, percentages of consonants correct (PCC), phonological processes, and mean length of utterance (MLU). Results revealed that there was no significant difference between the groups in their numbers of vocalizations (as there had been at age 2), although there continued to be differences in their phonetic inventories, PCC scores, and overall intelligibility. These findings suggest that at age 2 the children with SU-E were not only less phonologically skilled but less talkative, whereas by age 3 they were equally vocal. Analysis of the phonetic inventories of the children demonstrated that for most consonants, the SLI-E group followed the some pattern of development as the comparison children, but more of the normally developing group had productive control of each consonant, consistent with findings of Rescorla and Ratner. There continued to be differences in intelligibility as measured by rates of verbalization (those utterances with at least one intelligible word) and fully intelligible utterances. Using these measures, we found that approximately half the SU-E children had caught up with their normally developing peers in terms of articulation, whereas half of them continued to be significantly delayed. Finally, although some of the late-bloomer group had caught up to the comparison children in language skills, as measured by MLU, many had not, suggesting that there was a tendency for the children to catch up in some articulation skills before catching up in language abilities.

Child, Preschool↗
PubMed2001

The influence of maxillary central incisor position in complete dentures on /s/ sound production.

STATEMENT OF PROBLEM: The insertion of prosthodontic restorations often leads to speech defects, most of which are transient but nevertheless a source of concern to the patient. For the dental practitioner, there are few guidelines on designing a prosthetic restoration with maximum phonetic success. PURPOSE: This study investigated the effect of different maxillary central incisor positions on phonetic patterns. MATERIAL AND METHODS: The inclination angle of central incisor blocks in duplicate complete maxillary dentures was changed in a range of -30 degrees to +30 degrees from the original position (0 degrees). Test words and sentences were acoustically analyzed. Spectral parameters such as first peak, noise band (defined by upper and lower limits of the most intensively blackened frequency area), Fast Fourier Transformation power spectrum, energy spectrum, and time were investigated. Influences of oral stereognosis, hearing, and age as cofactors on /s/ articulation were also taken into account. RESULTS: The change of incisor block angle in both directions usually caused a poorer execution of the /s/ sound. The labial angulation seemed to have a greater effect than the palatal angulation. The most significant changes were those in the noise band and energy spectrum. CONCLUSION: Immediate phonetic adaptation of prosthetic restorations in the maxillary incisor region can be achieved only if the original position of the natural teeth is transferred to the denture. Although these misarticulations are, in most cases, likely to disappear within a few weeks, they may persist and even lead to psychosocial problems. A better understanding of the causes of misarticulation and the limits of adaptation according to certain morphologic parameters of dentures is important.

Adaptation, Physiological↗
PubMedDate not supplied

Levels of complexity in phonological disorders: evidence from Cantonese.

Longitudinal data from ten phonologically disordered Cantonese-speaking boys were analysed for distinctive features (manner and place). The children labelled 95 pictures, attempting each initial Cantonese segment at least five times. The applicability of Dinnsen et al.'s implicational hierarchy to this data was examined. Categorization of each child's system according to an implicational hierarchy was successful for nine of the ten children when phonetic inventories were considered. In addition, a phonemic inventory based on Dinnsen et al.'s phonetic inventory captured the system of phonological contrasts used by eight of the ten children. The patterns of the children who did not match the hierarchy were considered deviant rather than delayed. The ability of the hierarchy to predict the route of development in this group of children was also examined. The hierarchies (both phonetic and phonemic) successfully predicted the route of change in these cases. Implications for the use of an implicational hierarchy in phonological assessment and treatment are discussed. Further research on feature-based phonological development, in both typically-developing and disordered phonological systems is required.

Articulation Disorders↗
PubMed2002

Stability of memory traces for speech sounds in cochlear implant patients.

For this study, we examined the perception and production of vowels by postlingually deafened patients with cochlear implant. Four patients and one normally hearing subject produced typical vowel sounds of Finnish by using a speech synthesizer. Also acoustic analyses of the pronounced vowels were made. The first (F1) and the second (F2) formant frequencies were measured. The mismatch negativity (MMN), a cortical cognitive auditory event related potential, was used to measure objectively the patients' preattentive discrimination of a prototypical /i/ sound from deviants differing in the F2 continuum. In the phonetic tests the hyperspace effect was seen also among the patients. The MMN, which reflects the phonetic discrimination ability, could be identified from the patient with the best vowel perception abilities. The phonetic memory traces once developed for vowels seem to remain quite stable even though they have not been activated by vowel information for years.

Adult↗
PubMed1997

Some considerations in evaluating spoken word recognition by normal-hearing, noise-masked normal-hearing, and cochlear implant listeners. I: The effects of response format.

OBJECTIVE: The purpose of the present studies was to assess the validity of using closed-set response formats to measure two cognitive processes essential for recognizing spoken words---perceptual normalization (the ability to accommodate acoustic-phonetic variability) and lexical discrimination (the ability to isolate words in the mental lexicon). In addition, the experiments were designed to examine the effects of response format on evaluation of these two abilities in normal-hearing (NH), noise-masked normal-hearing (NMNH), and cochlear implant (CI) subject populations. DESIGN: The speech recognition performance of NH, NMNH, and CI listeners was measured using both open- and closed-set response formats under a number of experimental conditions. To assess talker normalization abilities, identification scores for words produced by a single talker were compared with recognition performance for items produced by multiple talkers. To examine lexical discrimination, performance for words that are phonetically similar to many other words (hard words) was compared with scores for items with few phonetically similar competitors (easy words). RESULTS: Open-set word identification for all subjects was significantly poorer when stimuli were produced in lists with multiple talkers compared with conditions in which all of the words were spoken by a single talker. Open-set word recognition also was better for lexically easy compared with lexically hard words. Closed-set tests, in contrast, failed to reveal the effects of either talker variability or lexical difficulty even when the response alternatives provided were systematically selected to maximize confusability with target items. CONCLUSIONS: These findings suggest that, although closed-set tests may provide important information for clinical assessment of speech perception, they may not adequately evaluate a number of cognitive processes that are necessary for recognizing spoken words. The parallel results obtained across all subject groups indicate that NH, NMNH, and CI listeners engage similar perceptual operations to identify spoken words. Implications of these findings for the design of new test batteries that can provide comprehensive evaluations of the individual capacities needed for processing spoken language are discussed.

Adult↗
PubMed2004

Falling on sensitive ears: constraints on bilingual lexical activation.

Spoken word recognition is characterized by multiple activation of sound patterns that are consistent with the acoustic-phonetic input. Recently, an extreme form of multiple activation was observed: Bilingual listeners activated words from both languages that were consistent with the input. We explored the degree to which bilingual multiple activation may be constrained by fine-grained acoustic-phonetic information. In a head-mounted eyetracking experiment, we presented Spanish-English bilinguals with spoken Spanish words having word-initial stop consonants with either English- or Spanish-appropriate voice onset times. Participants fixated interlingual distractors (nontarget pictures whose English names shared a phonological similarity with the Spanish targets) more frequently than control distractors when the target words contained English-appropriate voice onset times. These results demonstrate that fine-grained acoustic-phonetic information and a precise match between input and representation are critical for parallel activation of two languages.

Blinking↗
PubMed1983

Coding of the speech spectrum in three time-varying sinusoids.

Recent perceptual experiments with normal adult listeners show that phonetic information can readily be conveyed by sinewave replicas of speech signals. These tonal patterns are made of three sinusoids set equal in frequency and amplitude to the respective peaks of the first three formants of natural-speech utterances. Unlike natural and most synthetic speech, the spectrum of sinusoidal patterns contains neither harmonics nor broadband formants, and is identified as grossly unnatural in voice timbre. Despite this drastic recoding of the short-time speech spectrum, listeners perceive the phonetic content if the temporal properties of spectrum variation are preserved. These observations suggest that phonetic perception may depend on properties of coherent spectrum variation, a second-order property of the acoustic signal, rather than any particular set of acoustic elements present in speech signals.

Humans↗
PubMed2001

Coherence in children's speech perception.

Studies with adults have demonstrated that acoustic cues cohere in speech perception such that two stimuli cannot be discriminated if separate cues bias responses equally, but oppositely, in each. This study examined whether this kind of coherence exists for children's perception of speech signals, a test that first required that a contrast be found for which adults and children show similar cue weightings. Accordingly, experiment 1 demonstrated that adults, 7-, and 5-year-olds weight F2-onset frequency and gap duration similarly in "spa" versus "sa" decisions. In experiment 2, listeners of these same ages made "same" or "not-the-same" judgments for pairs of stimuli in an AX paradigm when only one cue differed, when the two cues were set within a stimulus to bias the phonetic percept towards the same category (relative to the other stimulus in the pair), and when the two cues were set within a stimulus to bias the phonetic percept towards different categories. Unexpectedly, adults' results contradicted earlier studies: They were able to discriminate stimuli when the two cues conflicted in how they biased phonetic percepts. Results for 7-year-olds replicated those of adults, but were not as strong. Only the results of 5-year-olds revealed the kind of perceptual coherence reported by earlier studies for adults. Thus, it is concluded that perceptual coherence for speech signals is present from an early age, and in fact listeners learn to overcome it under certain conditions.

Adult↗
PubMed2003

Individual talker differences in voice-onset-time.

Individual talkers differ in the acoustic properties of their speech, and at least some of these differences are in acoustic properties relevant for phonetic perception. Recent findings from studies of speech perception have shown that listeners can exploit such differences to facilitate both the recognition of talkers' voices and the recognition of words spoken by familiar talkers. These findings motivate the current study, whose aim is to examine individual talker variation in a particular phonetically-relevant acoustic property, voice-onset-time (VOT). VOT is a temporal property that robustly specifies voicing in stop consonants. From the broad literature involving VOT, it appears that individual talkers differ from one another in their VOT productions. The current study confirmed this finding for eight talkers producing monosyllabic words beginning with voiceless stop consonants. Moreover, when differences in VOT due to variability in speaking rate across the talkers were factored out using hierarchical linear modeling, individual talkers still differed from one another in VOT, though these differences were attenuated. These findings provide evidence that VOT varies systematically from talker to talker and may therefore be one phonetically-relevant acoustic property underlying listeners' capacity to benefit from talker-specific experience.

Adolescent↗
PubMed2004

Vowel formant discrimination for high-fidelity speech.

The goal of this study was to establish the ability of normal-hearing listeners to discriminate formant frequency in vowels in everyday speech. Vowel formant discrimination in syllables, phrases, and sentences was measured for high-fidelity (nearly natural) speech synthesized by STRAIGHT [Kawahara et al., Speech Commun. 27, 187-207 (1999)]. Thresholds were measured for changes in F1 and F2 for the vowels /I, epsilon, ae, lambda/ in /bVd/ syllables. Experimental factors manipulated included phonetic context (syllables, phrases, and sentences), sentence discrimination with the addition of an identification task, and word position. Results showed that neither longer phonetic context nor the addition of the identification task significantly affected thresholds, while thresholds for word final position showed significantly better performance than for either initial or middle position in sentences. Results suggest that an average of 0.37 barks is required for normal-hearing listeners to discriminate vowel formants in modest length sentences, elevated by 84% compared to isolated vowels. Vowel formant discrimination in several phonetic contexts was slightly elevated for STRAIGHT-synthesized speech compared to formant-synthesized speech stimuli reported in the study by Kewley-Port and Zheng [J. Acoust. Soc. Am. 106, 2945-2958 (1999)]. These elevated thresholds appeared related to greater spectral-temporal variability for high-fidelity speech produced by STRAIGHT than for formant-synthesized speech.

Adult↗
PubMed2005

Statistical properties of infant-directed versus adult-directed speech: insights from speech recognition.

Previous studies have shown that infant-directed speech ('motherese') exhibits overemphasized acoustic properties which may facilitate the acquisition of phonetic categories by infant learners. It has been suggested that the use of infant-directed data for training automatic speech recognition systems might also enhance the automatic learning and discrimination of phonetic categories. This study investigates the properties of infant-directed vs. adult-directed speech from the point of view of the statistical pattern recognition paradigm underlying automatic speech recognition. Isolated-word speech recognizers were trained on adult-directed vs. infant-directed data sets and were tested on both matched and mismatched data. Results show that recognizers trained on infant-directed speech did not always exhibit better recognition performance; however, their relative loss in performance on mismatched data was significantly less severe than that of recognizers trained on adult-directed speech and presented with infant-directed test data. An analysis of the statistical distributions of a subset of phonetic classes in both data sets showed that this pattern is caused by larger class overlaps in infant-directed speech. This finding has implications for both automatic speech recognition and theories of infant speech perception.

Adult↗