Katarina L. Haley

Stop-consonant and vowel perception in 3- and 4-year-old children.

Recent research on 5- to 11-year-old childrens perception of stop consonants and vowels indicates that they can generally identify these sounds with relatively high accuracy from short duration stimulus onsets [Ohde et al., J. Acoust. Soc. Am. 97, 3800-3812 (1995); Ohde et al., J. Acoust. Soc. Am. 100, 3813-3824 (1996)]. The purpose of the current experiments was to determine if younger children, aged 3-4 years, can also recover consonant and vowel features from stimulus onsets. Ten adults, ten 3-year olds, and ten 4-year-olds listened to synthesized syllables composed of combinations of [b d g] and [i u a]. The synthesis parameters included manipulations of the following stimulus variables: formant transition (moving or straight), noise burst (present or absent), and voicing duration (10, 30, or 46 ms). Developmental effects were found for the perception of both stop consonants and vowels. In general, adults identified these sounds at a significantly higher level than children, and perception by 4-year-olds was significantly better than 3-year-olds. A developmental effect of dynamic formant motion was obtained, but it was limited to only the [g] stop consonant. Stimulus duration affected the childrens perception of vowels indicating that they may utilize additional auditory information to a much greater extent than adults. The results support the importance of information in stimulus onsets for syllable identification, and developmental changes in sensitivity to these cues for consonant and vowel perception.

A developmental study of the perception of onset spectra for stop consonants in different vowel environments

The importance of different acoustic properties for the perception of place of articulation in prevocalic stop consonants was investigated from a developmental perspective. Eight adults and eight children in each of the age groups, 5, 6, 7, 9, and 11 years, listened to synthesized syllables comprised of all combinations of [b d g] and [i a]. The synthesis parameters were adapted from Blumstein and Stevens [J. Acoust. Soc. Am. 67, 648-662 (1980)], and included manipulations of the following stimulus variables: formant transitions (moving or straight), noise burst (present or absent), and voicing duration (10 or 46 ms). Identification performance was high for all age groups across most stimulus types. Formant transition motion generally was not necessary for accurate identification, and there was no difference between age groups in terms of the perceptual weight placed on this cue. Furthermore, the results did not support the salience of duration as a developmental cue to place of articulation. The presence of a burst improved identification for the velar and alveolar places of articulation for all age groups, but was particularly important for the 11-year-olds and adults. These findings indicate that children, by age 5, do not rely on dynamic formant motion any more than adults do, and that the ability to integrate acoustic cues across regions of spectral change shows developmental patterns.

A developmental study of vowel perception from brief synthetic consonant-vowel syllables

The purpose of this study was to assess the perceptual role of brief synthetic consonant-vowel syllables as cues for vowel perception in children and adults. Nine types of consonant-vowel syllables comprised of the stops [b d g] followed by the vowels [i a u] were synthesized. Stimuli were generated with durations of 10, 30, or 46 ms, and with or without formant transition motion. Eight children at each of five age levels (5, 6, 7, 9, and 11 years) and a control group of eight adults were trained to identify each vowel in a three-alternative forced-choice (3AFC) paradigm. The results showed that children and adults extracted vowel information at a generally high level from stimuli as brief as 10 ms. For many stimuli, there was little or no difference between the performance of children and adults. However, developmental effects were observed. First, the accuracy of vowel perception was more influenced by the consonant context for children than for adults. Whereas perception was similar across age levels for stimuli in the alveolar context, the youngest children perceived vowels in the labial and velar contexts at significantly lower levels than adults. Second, children were more affected by variations in stimulus duration than were adults. This finding was particularly prominent for the syllable [ga], where the dependency on duration decreased with age in a nearly linear fashion. These findings are discussed in relation to current hypotheses of vowel perception in adults, and hypotheses of speech perception development.

Foreign accent syndrome due to conversion disorder: Phonetic analyses and clinical course

Abstract We describe the case of a 36-year-old native speaker of English who began using a foreign accent after abrupt onset of problems involving multiple sensory and motor functions. Neurological and neuroradiological examinations were within normal limits and no organic explanation for the difficulties could be identified. After eight months, the patient made a full recovery, allowing a detailed comparison between the speech patterns displayed during the period of foreign accent and those of her typical speech. Perceptual and acoustic analyses showed specific changes in vowel and consonant production and in intonation and stress patterns during the accented speech. These changes were similar to those described in the literature for patients with foreign accent syndrome following left cerebral hemisphere lesions. A review of presenting symptoms and clinical course of our case, however, indicated strong evidence for a conversion disorder. This case demonstrates that a psychogenic etiology for foreign accent syndrome should sometimes be considered and that the prognosis for recovery, including spontaneous remission, may be good in such cases. Differential diagnosis between psychogenic and neurogenic etiologies is discussed relative to the case presentation, history, course, and recovery.

Publications Received for Review

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Evaluating the spectral distinction between sibilant fricatives through a speaker-centered approach

This study was designed to examine the feasibility of using the spectral mean and/or spectral skewness to distinguish between alveolar and palato-alveolar fricatives produced by individual adult speakers of English. Five male and five female speaker participants produced 100 CVC words with an initial consonant /s/ or /ʃ/. The spectral mean and skewness were derived every 10 milliseconds throughout the fricative segments and plotted for all productions. Distinctions were examined for each speaker through visual inspection of these time history plots and statistical comparisons were completed for analysis windows centered 50 ms after the onset of the fricative segment. The results showed significant differences between the alveolar and palato-alveolar fricatives for both the mean and skewness values. However, there was considerable inter-speaker overlap, limiting the utility of the measures to evaluate the adequacy of the phonetic distinction. When the focus shifted to individual speakers rather than average group performance, only the spectral mean distinguished consistently between the two phonetic categories. The robustness of the distinction suggests that intra-speaker overlap in spectral mean between prevocalic /s/ and /ʃ/ targets may be indicative of abnormal fricative production and a useful measure for clinical applications.

Phonetic properties of aphasic-apraxic speech: A modified narrow transcription analysis

We used a modified narrow phonetic transcription procedure to examine a speech sample produced by 10 speakers with coexisting aphasia and apraxia of speech. The transcription protocol was limited to eight diacritic marks selected based on previous perceptual descriptions of phonetic distortion among speakers with pure apraxia of speech. Additionally, there was one general distortion category for perceived distortions not captured by the main diacritic marks. The results showed that distortion errors were as common as substitution errors, that vowel and consonant segments were equally vulnerable to misproduction, and that there was no difference between the frequency of consonants produced incorrectly in prevocalic and postvocalic syllable positions. Among distortion errors, 32% were classified as segment prolongations and 41% were classified as general distortions. An independent transcription that used a comprehensive system of diacritic marks was performed as a follow-up. Most general distortions were not further specified by the comprehensive transcription system. A phonetic contrast analysis of errors detected at the broad transcription level yielded different speech characteristics from the observed distortion errors, but were in general correspondence with previously reported error patterns in intelligibility testing of the same speech sample. The results are discussed relative to the role of single word intelligibility testing in aphasia and apraxia of speech assessment and the challenges associated with transcribing disordered speech.

Single word intelligibility in aphasia and apraxia of speech

Abstract Single word speech intelligibility was evaluated in three groups : aphasia with apraxia of speech, aphasia with no apraxia of speech, and normal controls. Intelligibility was significantly lower in the two aphasic groups compared with the normal group and intelligibility did not differ significantly between the aphasia and apraxia of speech and the aphasia only groups. Seventy per cent of the speakers with apraxia of speech obtained intelligibility scores below the normal range and 80% of the speakers with aphasia only obtained intelligibility scores within the normal range. There was a moderate, but statistically nonsignificant, correlation between intelligibility and severity of apraxia of speech on an eight-point rating scale.

Word length and vowel duration in apraxia of speech: The use of relative measures

Previous research has established that the duration of stressed word stem vowels is shorter in polysyllabic words than in monosyllabic words for normal speakers and for speakers with aphasia and apraxia of speech (AOS). However, the results are inconsistent across studies with regard to the magnitude and pattern of the duration reduction for apraxic speakers. We hypothesized that this inconsistency may be explained based on different relative measures of duration reduction. A speech sample was obtained from 10 aphasic speakers with AOS, 10 aphasic speakers without AOS, and 10 normal controls. As predicted, the use of two different relative measures resulted in different vowel reduction patterns, both of which were consistent with previous reports. The results further indicate that the production of polysyllabic words is particularly taxing in AOS and is associated with a substantial reduction of speaking rate compared to other aphasic and normal speakers.

Supporting autonomy for people with aphasia: Use of the life interests and values (LIV) cards

Abstract Background: People with aphasia (PWA) are frequently disregarded as reliable respondents because their language problems may restrict their responses to oral and written questioning. Consequently, family members are often asked to speak on their behalf. The Life Interests and Values (LIV) Cards are a nonlinguistic, picture-based instrument designed for communicating directly with PWA about their current and desired life activities. Purpose: The goals of this study were to (1) explore utility of LIV Cards for interviewing PWA and (2) examine congruence between responses of PWA and proxies. Method: Study participants were 10 PWA with varying language and cognitive abilities and 10 family member proxies. Both groups participated in LIV Card interviews to identify current and preferred activities of the PWA. Core interview times for the PWA and percentage of selected activities for 4 activity categories were calculated, as was item-by-item response congruency between PWA and proxies. Results: All 10 PWA completed LIV Cards interviews in 45 minutes or less. There were individualized response patterns regarding activity participation and preferences. Mean point-to-point agreement between PWA and their proxies was 74% for current activities and 71% for activity preferences of the PWA. Conclusions: PWA were able to provide information about their current and preferred involvement in life activities through use of the LIV Cards. Family members did not predict activity choices and desires of PWA with full accuracy. The LIV Cards appear to be a viable tool for setting goals and discussing life priorities of PWA.