Joanna H. Lowenstein

Patterns of acquisition of native voice onset time in English-learning children

Learning to speak involves both mastering the requisite articulatory gestures of ones native language and learning to coordinate those gestures according to the rules of the language. Voice onset time (VOT) acquisition illustrates this point: The child must learn to produce the necessary upper vocal tract and laryngeal gestures and to coordinate them with very precise timing. This longitudinal study examined the acquisition of English VOT by audiotaping seven children at 2 month intervals from first words (around 15 months) to the appearance of three-word sentences (around 30 months) in spontaneous speech. Words with initial stops were excerpted, and (1) the numbers of words produced with intended voiced and voiceless initial stops were counted; (2) VOT was measured; and (3) within-child standard deviations of VOT were measured. Results showed that children (1) initially avoided saying words with voiceless initial stops, (2) initially did not delay the onset of the laryngeal adduction relative to the release of closure as long as adults do for voiceless stops, and (3) were more variable in VOT for voiceless than for voiced stops. Overall these results support a model of acquisition that focuses on the mastery of gestural coordination as opposed to the acquisition of segmental contrasts.

Emergent literacy in kindergartners with cochlear implants

Objective: A key ingredient to academic success is being able to read. Deaf individuals have historically failed to develop literacy skills comparable with those of their normal-hearing (NH) peers, but early identification and cochlear implants (CIs) have improved prospects such that these children can learn to read at the levels of their peers. The goal of this study was to examine early, or emergent, literacy in these children. Method: Twenty-seven deaf children with CIs, who had just completed kindergarten were tested on emergent literacy, and on cognitive and linguistic skills that support emergent literacy, specifically ones involving phonological awareness, executive functioning, and oral language. Seventeen kindergartners with NH and eight with hearing loss, but who used hearing aids served as controls. Outcomes were compared for these three groups of children, regression analyses were performed to see whether predictor variables for emergent literacy differed for children with NH and those with CIs, and factors related to the early treatment of hearing loss and prosthesis configuration were examined for children with CIs. Results: The performance of children with CIs was roughly 1 SD or more below the mean performance of children with NH on all tasks, except for syllable counting, reading fluency, and rapid serial naming. Oral language skills explained more variance in emergent literacy for children with CIs than for children with NH. Age of first implant explained moderate amounts of variance for several measures. Having one or two CIs had no effect, but children who had some amount of bimodal experience outperformed children who had none on several measures. Conclusions: Even deaf children who have benefitted from early identification, intervention, and implantation are still at risk for problems with emergent literacy that could affect their academic success. This finding means that intensive language support needs to continue through at least the early elementary grades. Also, a period of bimodal stimulation during the preschool years can help boost emergent literacy skills to some extent.

Children Discover the Spectral Skeletons in Their Native Language before the Amplitude Envelopes.

Much of speech perception research has focused on brief spectro-temporal properties in the signal, but some studies have shown that adults can recover linguistic form when those properties are absent. In this experiment, 7-year-old English-speaking children demonstrated adultlike abilities to understand speech when only sine waves (SWs) replicating the 3 lowest resonances of the vocal tract were presented, but they failed to demonstrate comparable abilities when noise bands amplitude-modulated with envelopes derived from the same signals were presented. In contrast, adults who were not native English speakers but who were competent 2nd-language learners were worse at understanding both kinds of stimuli than native English-speaking adults. Results showed that children learn to extract linguistic form from signals that preserve some spectral structure, even if degraded, before they learn to do so for signals that preserve only amplitude structure. The authors hypothesize that childrens early sensitivity to global spectral structure reflects the role that it may play in language learning.

Working memory in children with cochlear implants: problems are in storage, not processing.

BACKGROUND There is growing consensus that hearing loss and consequent amplification likely interact with cognitive systems. A phenomenon often examined in regards to these potential interactions is working memory, modeled as consisting of one component responsible for storage of information and another component responsible for processing of that information. Signal degradation associated with cochlear implants should selectively inhibit storage without affecting processing. This study examined two hypotheses: (1) A single task can be used to measure storage and processing in working memory, with recall accuracy indexing storage and rate of recall indexing processing; (2) Storage is negatively impacted for children with CIs, but not processing. METHOD Two experiments were conducted. Experiment 1 included adults and children, 8 and 6 years of age, with NH. Procedures tested the prediction that accuracy of recall could index storage and rate of recall could index processing. Both measures were obtained during a serial-recall task using word lists designed to manipulate storage and processing demands independently: non-rhyming nouns were the standard condition; rhyming nouns were predicted to diminish storage capacity; and non-rhyming adjectives were predicted to increase processing load. Experiment 2 included 98 8-year-olds, 48 with NH and 50 with CIs, in the same serial-recall task using the non-rhyming and rhyming nouns. RESULTS Experiment 1 showed that recall accuracy was poorest for the rhyming nouns and rate of recall was slowest for the non-rhyming adjectives, demonstrating that storage and processing can be indexed separately within a single task. In Experiment 2, children with CIs showed less accurate recall of serial order than children with NH, but rate of recall did not differ. Recall accuracy and rate of recall were not correlated in either experiment, reflecting independence of these mechanisms. CONCLUSIONS It is possible to measure the operations of storage and processing mechanisms in working memory in a single task, and only storage is impaired for children with CIs. These findings suggest that research and clinical efforts should focus on enhancing the saliency of representation for children with CIs. Direct instruction of syntax and semantics could facilitate storage in real-world working memory tasks.

Sensitivity to structure in the speech signal by children with speech sound disorder and reading disability

PURPOSE Children with speech sound disorder (SSD) and reading disability (RD) have poor phonological awareness, a problem believed to arise largely from deficits in processing the sensory information in speech, specifically individual acoustic cues. However, such cues are details of acoustic structure. Recent theories suggest that listeners also need to be able to integrate those details to perceive linguistically relevant form. This study examined abilities of children with SSD, RD, and SSD+RD not only to process acoustic cues but also to recover linguistically relevant form from the speech signal. METHOD Ten- to 11-year-olds with SSD (n=17), RD (n=16), SSD+RD (n=17), and Controls (n=16) were tested to examine their sensitivity to (1) voice onset times (VOT); (2) spectral structure in fricative-vowel syllables; and (3) vocoded sentences. RESULTS Children in all groups performed similarly with VOT stimuli, but children with disorders showed delays on other tasks, although the specifics of their performance varied. CONCLUSION Children with poor phonemic awareness not only lack sensitivity to acoustic details, but are also less able to recover linguistically relevant forms. This is contrary to one of the main current theories of the relation between spoken and written language development. LEARNING OUTCOMES Readers will be able to (1) understand the role speech perception plays in phonological awareness, (2) distinguish between segmental and global structure analysis of speech perception, (3) describe differences and similarities in speech perception among children with speech sound disorder and/or reading disability, and (4) recognize the importance of broadening clinical interventions to focus on recognizing structure at all levels of speech analysis.

What is the deficit in phonological processing deficits: Auditory sensitivity, masking, or category formation?

Although children with language impairments, including those associated with reading, usually demonstrate deficits in phonological processing, there is minimal agreement as to the source of those deficits. This study examined two problems hypothesized to be possible sources: either poor auditory sensitivity to speech-relevant acoustic properties, mainly formant transitions, or enhanced masking of those properties. Adults and 8-year-olds with and without phonological processing deficits (PPD) participated. Children with PPD demonstrated weaker abilities than children with typical language development (TLD) in reading, sentence recall, and phonological awareness. Dependent measures were word recognition, discrimination of spectral glides, and phonetic judgments based on spectral and temporal cues. All tasks were conducted in quiet and in noise. Children with PPD showed neither poorer auditory sensitivity nor greater masking than adults and children with TLD, but they did demonstrate an unanticipated deficit in category formation for nonspeech sounds. These results suggest that these children may have an underlying deficit in perceptually organizing sensory information to form coherent categories.

Do Adults With Cochlear Implants Rely on Different Acoustic Cues for Phoneme Perception Than Adults With Normal Hearing

PURPOSE Several acoustic cues specify any single phonemic contrast. Nonetheless, adult, native speakers of a language share weighting strategies, showing preferential attention to some properties over others. Cochlear implant (CI) signal processing disrupts the salience of some cues: In general, amplitude structure remains readily available, but spectral structure less so. This study asked how well speech recognition is supported if CI users shift attention to salient cues not weighted strongly by native speakers. METHOD Twenty adults with CIs participated. The /bɑ/-/wɑ/ contrast was used because spectral and amplitude structure varies in correlated fashion for this contrast. Adults with normal hearing weight the spectral cue strongly but the amplitude cue negligibly. Three measurements were made: labeling decisions, spectral and amplitude discrimination, and word recognition. RESULTS Outcomes varied across listeners: Some weighted the spectral cue strongly, some weighted the amplitude cue, and some weighted neither. Spectral discrimination predicted spectral weighting. Spectral weighting explained the most variance in word recognition. Age of onset of hearing loss predicted spectral weighting but not unique variance in word recognition. CONCLUSION The weighting strategies of listeners with normal hearing likely support speech recognition best, so efforts in implant design, fitting, and training should focus on developing those strategies.

Improving speech-in-noise recognition for children with hearing loss: potential effects of language abilities, binaural summation, and head shadow.

Abstract Objective: This study examined speech recognition in noise for children with hearing loss, compared it to recognition for children with normal hearing, and examined mechanisms that might explain variance in childrens abilities to recognize speech in noise. Design: Word recognition was measured in two levels of noise, both when the speech and noise were co-located in front and when the noise came separately from one side. Four mechanisms were examined as factors possibly explaining variance: vocabulary knowledge, sensitivity to phonological structure, binaural summation, and head shadow. Study sample: Participants were 113 eight-year-old children. Forty-eight had normal hearing (NH) and 65 had hearing loss: 18 with hearing aids (HAs), 19 with one cochlear implant (CI), and 28 with two CIs. Results: Phonological sensitivity explained a significant amount of between-groups variance in speech-in-noise recognition. Little evidence of binaural summation was found. Head shadow was similar in magnitude for children with NH and with CIs, regardless of whether they wore one or two CIs. Children with HAs showed reduced head shadow effects. Conclusion: These outcomes suggest that in order to improve speech-in-noise recognition for children with hearing loss, intervention needs to be comprehensive, focusing on both language abilities and auditory mechanisms.

Does harmonicity explain children's cue weighting of fricative-vowel syllables?

When labeling syllable-initial fricatives, children have been found to weight formant transitions more and fricative-noise spectra less than adults, prompting the suggestion that children attend more to the slow vocal-tract movements that create syllabic structure than to the rapid gestures more closely aligned with individual phonetic segments. That explanation fits well with linguistic theories, but an alternative explanation emerges from auditory science: Perhaps children attend to formant transitions because they are found in voiced signal portions, and so formants share a common harmonic structure. This work tested that hypothesis by using two kinds of stimuli lacking harmonicity: sine-wave and whispered speech. Adults and children under 7 years of age were asked to label fricative-vowel syllables in each of those conditions, as well as natural speech. Results showed that children did not change their weighting strategies from those used with natural speech when listening to sine-wave stimuli, but weighted formant transitions less when listening to whispered stimuli. These findings showed that it is not the harmonicity principle that explains childrens preference for formant transitions in phonetic decisions. It is further suggested that children are unable to recover formant structure when those formants are not spectrally prominent and/or are noisy.

Nonword repetition in children with cochlear implants: A potential clinical marker of poor language acquisition

PURPOSE Cochlear implants (CIs) can facilitate the acquisition of spoken language for deaf children, but challenges remain. Language skills dependent on phonological sensitivity are most at risk for these children, so having an effective way to diagnose problems at this level would be of value for school speech-language pathologists. The goal of this study was to assess whether a nonword repetition (NWR) task could serve that purpose. METHOD Participants were 104 second graders: 49 with normal hearing (NH) and 55 with CIs. In addition to NWR, children were tested on 10 measures involving phonological awareness and processing, serial recall of words, vocabulary, reading, and grammar. RESULTS Children with CIs performed more poorly than children with NH on NWR, and sensitivity to phonological structure alone explained that performance for children in both groups. For children with CIs, 2 audiological factors positively influenced outcomes on NWR: being identified with hearing loss at a younger age and having experience with wearing a hearing aid on the unimplanted ear at the time of receiving a 1st CI. NWR scores were better able to rule out than to rule in such language deficits. CONCLUSIONS Well-designed NWR tasks could have clinical utility in assessments of language acquisition for school-age children with CIs.