Spoken word recognition in toddlers who use cochlear implants

Association of domain-general speed of information processing with spoken language outcomes in prelingually-deaf children with cochlear implants

Spoken language development after pediatric cochlear implantation requires rapid and efficient processing of novel, degraded auditory signals and linguistic information. These demands for rapid adaptation tax the information processing speed ability of children who receive cochlear implants. This study investigated the association of speed of information processing ability with spoken language outcomes after cochlear implantation in prelingually deaf children aged 4-6 years. Two domain-general (visual, non-linguistic) speed of information processing measures were administered to 21 preschool-aged children with cochlear implants and 23 normal-hearing peers. Measures of speech recognition, language (vocabulary and comprehension), nonverbal intelligence, and executive functioning skills were also obtained from each participant. Speed of information processing was positively associated with speech recognition and language skills in preschool-aged children with cochlear implants but not in normal-hearing peers. This association remained significant after controlling for hearing group, age, nonverbal intelligence, and executive functioning skills. These findings are consistent with models suggesting that domain-general, fast-efficient information processing speed underlies adaptation to speech perception and language learning following implantation. Assessment and intervention strategies targeting speed of information processing may provide better understanding and development of speech-language skills after cochlear implantation.

Verbal Fluency in Prelingually Deaf, Early Implanted Children and Adolescents With Cochlear Implants

PURPOSE

Verbal fluency tasks assess the ability to quickly and efficiently retrieve words from the mental lexicon by requiring subjects to rapidly generate words within a phonological or semantic category. This study investigated differences between cochlear implant users and normal-hearing peers in the clustering and time course of word retrieval during phonological and semantic verbal fluency tasks.

METHOD

Twenty-eight children and adolescents (aged 9-17 years) with cochlear implants and 33 normal-hearing peers completed measures of verbal fluency, nonverbal intelligence, speech perception, and verbal short-term/working memory. Phonological and semantic verbal fluency tests were scored for total words generated, words generated in each 10-s interval of the 1-min task, latency to first word generated, number of word clusters, average cluster size, and number of word/cluster switches.

RESULTS

Children and adolescents with cochlear implants generated fewer words than normal-hearing peers throughout the entire 60-s time interval of the phonological and semantic fluency tasks. Cochlear implant users also had slower start latency times and produced fewer clusters and switches than normal-hearing peers during the phonological fluency task. Speech perception and verbal working memory scores were more strongly associated with verbal fluency scores in children and adolescents with cochlear implants than in normal-hearing peers.

CONCLUSIONS

Cochlear implant users show poorer phonological and semantic verbal fluency than normal-hearing peers, and their verbal fluency is significantly associated with speech perception and verbal working memory. These findings suggest deficits in fluent retrieval of phonological and semantic information from long-term lexical memory in cochlear implant users.

Delayed Lexical Access and Cascading Effects on Spreading Semantic Activation During Spoken Word Recognition in Children With Hearing Aids and Cochlear Implants: Evidence From Eye-Tracking

OBJECTIVE

The objective of this study was to characterize the dynamics of real-time lexical access, including lexical competition among phonologically similar words, and spreading semantic activation in school-age children with hearing aids (HAs) and children with cochlear implants (CIs). We hypothesized that developing spoken language via degraded auditory input would lead children with HAs or CIs to adapt their approach to spoken word recognition, especially by slowing down lexical access.

DESIGN

Participants were children ages 9- to 12-years old with normal hearing (NH), HAs, or CIs. Participants completed a Visual World Paradigm task in which they heard a spoken word and selected the matching picture from four options. Competitor items were either phonologically similar, semantically similar, or unrelated to the target word. As the target word unfolded, children's fixations to the target word, cohort competitor, rhyme competitor, semantically related item, and unrelated item were recorded as indices of ongoing lexical access and spreading semantic activation.

RESULTS

Children with HAs and children with CIs showed slower fixations to the target, reduced fixations to the cohort competitor, and increased fixations to the rhyme competitor, relative to children with NH. This wait-and-see profile was more pronounced in the children with CIs than the children with HAs. Children with HAs and children with CIs also showed delayed fixations to the semantically related item, although this delay was attributable to their delay in activating words in general, not to a distinct semantic source.

CONCLUSIONS

Children with HAs and children with CIs showed qualitatively similar patterns of real-time spoken word recognition. Findings suggest that developing spoken language via degraded auditory input causes long-term cognitive adaptations to how listeners recognize spoken words, regardless of the type of hearing device used. Delayed lexical access directly led to delays in spreading semantic activation in children with HAs and CIs. This delay in semantic processing may impact these children's ability to understand connected speech in everyday life.

Vocabulary Growth in Mandarin-Speaking Children With Bilateral Cochlear Implants, Bimodal Stimulation, or Unilateral Cochlear Implants During the First Year After Activation

PURPOSE

The purpose of this study was to evaluate vocabulary development in Mandarin-speaking children with bilateral cochlear implants (CIs), bimodal stimulation (CI plus hearing aids [HAs]), or unilateral CIs during the first year after CI activation.

METHOD

Participants included 23 children with simultaneous bilateral CIs, 23 children with bimodal stimulation, and 15 children with unilateral CIs. They all received CIs before 30 months of age. Parents were asked to endorse words that their child could understand only or understand and say using the Early Vocabulary Inventory for Mandarin Chinese at the day of CI activation and 1, 3, 6, 9, and 12 months after CI activation. Receptive and expressive vocabulary sizes were computed.

RESULTS

Growth curve analysis revealed that children with simultaneous bilateral CIs demonstrated faster growth of receptive vocabulary than those with bimodal stimulation, followed by those with unilateral CIs. Moreover, children with simultaneous bilateral CIs reached the 100-word mark for receptive vocabulary earlier than children with bimodal stimulation, followed by those with unilateral CIs. There were no significant differences among the three groups in expressive vocabulary.

CONCLUSIONS

Bilateral CIs have an advantage over bimodal stimulation in early receptive vocabulary development in Mandarin, a tone language. HA usage is still recommended for those who receive one CI.

Children's syntactic parsing and sentence comprehension with a degraded auditory signal

During sentence comprehension, young children anticipate syntactic structures using early-arriving words and have difficulties revising incorrect predictions using late-arriving words. However, nearly all work to date has focused on syntactic parsing in idealized speech environments, and little is known about how children's strategies for predicting and revising meanings are affected by signal degradation. This study compares comprehension of active and passive sentences in natural and vocoded speech. In a word-interpretation task, 5-year-olds inferred the meanings of novel words in sentences that (1) encouraged agent-first predictions (e.g., The blicket is eating the seal implies The blicket is the agent), (2) required revising predictions (e.g., The blicket is eaten by the seal implies The blicket is the theme), or (3) weakened predictions by placing familiar nouns in sentence-initial position (e.g., The seal is eating/eaten by the blicket). When novel words promoted agent-first predictions, children misinterpreted passives as actives, and errors increased with vocoded compared to natural speech. However, when familiar words were sentence-initial that weakened agent-first predictions, children accurately interpreted passives, with no signal-degradation effects. This demonstrates that signal quality interacts with interpretive processes during sentence comprehension, and the impacts of speech degradation are greatest when late-arriving information conflicts with predictions.

Estimating the reduced benefit of infant-directed speech in cochlear implant-related speech processing

Caregivers modify their speech when talking to infants, a specific type of speech known as infant-directed speech (IDS). This speaking style facilitates language learning compared to adult-directed speech (ADS) in infants with normal hearing (NH). While infants with NH and those with cochlear implants (CIs) prefer listening to IDS over ADS, it is yet unknown how CI processing may affect the acoustic distinctiveness between ADS and IDS, as well as the degree of intelligibility of these. This study analyzed speech of seven female adult talkers to model the effects of simulated CI processing on (1) acoustic distinctiveness between ADS and IDS, (2) estimates of intelligibility of caregivers' speech in ADS and IDS, and (3) individual differences in caregivers' ADS-to-IDS modification and estimated speech intelligibility. Results suggest that CI processing is substantially detrimental to the acoustic distinctiveness between ADS and IDS, as well as to the intelligibility benefit derived from ADS-to-IDS modifications. Moreover, the observed variability across individual talkers in acoustic implementation of ADS-to-IDS modification and the estimated speech intelligibility was significantly reduced due to CI processing. The findings are discussed in the context of the link between IDS and language learning in infants with CIs.

Differential At-Risk Pediatric Outcomes of Parental Sensitivity Based on Hearing Status

Purpose The aim of this study was to investigate the role of parental sensitivity in language and neurocognitive outcomes in children who are deaf and/or hard of hearing (DHH). Method Sixty-two parent-child dyads of children with normal hearing (NH) and 64 of children who are DHH (3-8 years) completed parent and child measures of inhibitory control/executive functioning and child measures of sentence comprehension and vocabulary. The dyads also participated in a video-recorded, free-play interaction that was coded for parental sensitivity. Results There was no evidence of associations between parental sensitivity and inhibitory control or receptive language in children with NH. In contrast, parental sensitivity was related to children's inhibitory control and all language measures in children who are DHH. Moreover, inhibitory control significantly mediated the association between parental sensitivity and child language on the Clinical Evaluation of Language Fundamentals-Fifth Edition Following Directions subscale (6-8 years)/Clinical Evaluation of Language Fundamentals Preschool-Second Edition Concepts and Following Directions subscale (3-5 years). Follow-up analyses comparing subgroups of children who used hearing aids (n = 29) or cochlear implants (CIs; n = 35) revealed similar correlational trends, with the exception that parental sensitivity showed little relation to inhibitory control in the group of CI users. Conclusions Parental sensitivity is associated with at-risk language outcomes and disturbances in inhibitory control in young children who are DHH. Compared to children with NH, children who are DHH may be more sensitive to parental behaviors and their effects on emerging inhibitory control and spoken language. Specifically, inhibitory control, when scaffolded by positive parental behaviors, may be critically important for robust language development in children who are DHH.

Infants' Preference for Child-Directed Speech Over Time-Reversed Speech in On-Channel and Off-Channel Masking

Purpose This study aims to examine the development of auditory selective attention to speech in noise by examining the ability of infants to prefer child-directed speech (CDS) over time-reversed speech (TRS) presented in "on-channel" and "off-channel" noise. Method A total of 32 infants participated in the study. Sixteen typically developing infants were tested at 7 and 11 months of age using the central fixation procedure with CDS and TRS in two types of noise at +10 dB signal-to-noise ratio. One type of noise was an "on-channel" masker with a spectrum overlapping that of the CDS (energetic masking), and the second was an "off-channel" masker with frequencies that were outside the spectrum of the CDS (distractive masking). An additional group of sixteen 11-month-old infants were tested in quiet and served as controls for the "off-frequency" masker condition. Results Infants preferred CDS over TRS in both age groups, but this preference was more pronounced with "off-channel" masker regardless of age. Also, older infants demonstrated longer looking time for the target stimuli when presented with an "off-channel" masker compared to the "on-channel" masker. Looking time in quiet was similar to looking time in the "off-channel" condition, and looking time for CDS was longer in quiet compared to the "on-channel" condition. Conclusions These findings support the notion that (a) infants as young as 7 months of age are already showing preference for speech in noise, regardless of type of masker; (b) by 11 months of age, listening with the "off-channel" condition did not yield different results than in quiet. Thus, by 11 months of age, infants' cognitive-attentional abilities may be more developed.

The Impact of Hearing Experience on Children's Use of Phonological and Semantic Information During Lexical Access

Purpose The purpose of this study was to examine the extent to which phonological competition and semantic priming influence lexical access in school-aged children with cochlear implants (CIs) and children with normal acoustic hearing. Method Participants included children who were 5-10 years of age with either normal hearing (n = 41) or bilateral severe to profound sensorineural hearing loss and used CIs (n = 13). All participants completed a two-alternative forced-choice task while eye gaze to visual images was recorded and quantified during a word recognition task. In this task, the target image was juxtaposed with a competitor image that was either a phonological onset competitor (i.e., shared the same initial consonant-vowel-consonant syllable as the target) or an unrelated distractor. Half of the trials were preceded by an image prime that was semantically related to the target image. Results Children with CIs showed evidence of phonological competition during real-time processing of speech. This effect, however, was less and occurred later in the time course of speech processing than what was observed in children with normal hearing. The presence of a semantically related visual prime reduced the effects of phonological competition in both groups of children but to a greater degree in children with CIs. Conclusions Children with CIs were able to process single words similarly to their counterparts with normal hearing. However, children with CIs appeared to have increased reliance on surrounding semantic information compared to their normal-hearing counterparts.

Children With Cochlear Implants Use Semantic Prediction to Facilitate Spoken Word Recognition

Purpose Children with cochlear implants (CIs) are more likely to struggle with spoken language than their age-matched peers with normal hearing (NH), and new language processing literature suggests that these challenges may be linked to delays in spoken word recognition. The purpose of this study was to investigate whether children with CIs use language knowledge via semantic prediction to facilitate recognition of upcoming words and help compensate for uncertainties in the acoustic signal. Method Five- to 10-year-old children with CIs heard sentences with an informative verb (draws) or a neutral verb (gets) preceding a target word (picture). The target referent was presented on a screen, along with a phonologically similar competitor (pickle). Children's eye gaze was recorded to quantify efficiency of access of the target word and suppression of phonological competition. Performance was compared to both an age-matched group and vocabulary-matched group of children with NH. Results Children with CIs, like their peers with NH, demonstrated use of informative verbs to look more quickly to the target word and look less to the phonological competitor. However, children with CIs demonstrated less efficient use of semantic cues relative to their peers with NH, even when matched for vocabulary ability. Conclusions Children with CIs use semantic prediction to facilitate spoken word recognition but do so to a lesser extent than children with NH. Children with CIs experience challenges in predictive spoken language processing above and beyond limitations from delayed vocabulary development. Children with CIs with better vocabulary ability demonstrate more efficient use of lexical-semantic cues. Clinical interventions focusing on building knowledge of words and their associations may support efficiency of spoken language processing for children with CIs. Supplemental Material https://doi.org/10.23641/asha.14417627.

The effects of phonological neighborhood density in childhood word production and recognition in Russian are opposite to English

This study investigates how phonological neighborhood density (PND) affects word production and recognition in 4-to-6-year-old Russian children in comparison to adults. Previous experiments with English-speaking adults showed that a dense neighborhood facilitated word production but inhibited recognition whereas a sparse neighborhood inhibited production but facilitated recognition. Importantly, these effects are not universal because a reverse PND pattern was found in Spanish-speaking adults. Probably, PND effects depend on the morphological properties of language.This study focuses on PND effects in word production and recognition in terms of facilitation and inhibition in Russian. Our results are consistent with those in Spanish: Russian-speaking adults produced words with dense neighborhoods more slowly and recognized them faster than words with sparse neighborhoods. Russian children showed the same PND effect in recognition and no effect was found in production. The findings support the hypothesis that PND effects in word production and recognition are influenced by the morphological system of language.

Toddlers' fast-mapping from noise-vocoded speech

The ability to recognize speech that is degraded spectrally is a critical skill for successfully using a cochlear implant (CI). Previous research has shown that toddlers with normal hearing can successfully recognize noise-vocoded words as long as the signal contains at least eight spectral channels [Newman and Chatterjee. (2013). J. Acoust. Soc. Am. 133(1), 483-494; Newman, Chatterjee, Morini, and Remez. (2015). J. Acoust. Soc. Am. 138(3), EL311-EL317], although they have difficulty with signals that only contain four channels of information. Young children with CIs not only need to match a degraded speech signal to a stored representation (word recognition), but they also need to create new representations (word learning), a task that is likely to be more cognitively demanding. Normal-hearing toddlers aged 34 months were tested on their ability to initially learn (fast-map) new words in noise-vocoded stimuli. While children were successful at fast-mapping new words from 16-channel noise-vocoded stimuli, they failed to do so from 8-channel noise-vocoded speech. The level of degradation imposed by 8-channel vocoding appears sufficient to disrupt fast-mapping in young children. Recent results indicate that only CI patients with high spectral resolution can benefit from more than eight active electrodes. This suggests that for many children with CIs, reduced spectral resolution may limit their acquisition of novel words.

Quantifying the Effects of Background Speech Babble on Preschool Children's Novel Word Learning in a Multisession Paradigm: A Preliminary Study

Purpose This study tested the effects of background speech babble on novel word learning in preschool children with a multisession paradigm. Method Eight 3-year-old children were exposed to a total of 8 novel word-object pairs across 2 story books presented digitally. Each story contained 4 novel consonant-vowel-consonant nonwords. Children were exposed to both stories, one in quiet and one in the presence of 4-talker babble presented at 0-dB signal-to-noise ratio. After each story, children's learning was tested with a referent selection task and a verbal recall (naming) task. Children were exposed to and tested on the novel word-object pairs on 5 separate days within a 2-week span. Results A significant main effect of session was found for both referent selection and verbal recall. There was also a significant main effect of exposure condition on referent selection performance, with more referents correctly selected for word-object pairs that were presented in quiet compared to pairs presented in speech babble. Finally, children's verbal recall of novel words was statistically better than baseline performance (i.e., 0%) on Sessions 3-5 for words exposed in quiet, but only on Session 5 for words exposed in speech babble. Conclusions These findings suggest that background speech babble at 0-dB signal-to-noise ratio disrupts novel word learning in preschool-age children. As a result, children may need more time and more exposures of a novel word before they can recognize or verbally recall it.

Lexical bias in word recognition by cochlear implant listeners

When hearing an ambiguous speech sound, listeners show a tendency to perceive it as a phoneme that would complete a real word, rather than completing a nonsense/fake word. For example, a sound that could be heard as either /b/ or /ɡ/ is perceived as /b/ when followed by _ack but perceived as /ɡ/ when followed by "_ap." Because the target sound is acoustically identical across both environments, this effect demonstrates the influence of top-down lexical processing in speech perception. Degradations in the auditory signal were hypothesized to render speech stimuli more ambiguous, and therefore promote increased lexical bias. Stimuli included three speech continua that varied by spectral cues of varying speeds, including stop formant transitions (fast), fricative spectra (medium), and vowel formants (slow). Stimuli were presented to listeners with cochlear implants (CIs), and also to listeners with normal hearing with clear spectral quality, or with varying amounts of spectral degradation using a noise vocoder. Results indicated an increased lexical bias effect with degraded speech and for CI listeners, for whom the effect size was related to segment duration. This method can probe an individual's reliance on top-down processing even at the level of simple lexical/phonetic perception.

Sonority's Effect as a Surface Cue on Lexical Speech Perception of Children With Cochlear Implants

OBJECTIVES

Sonority is the relative perceptual prominence/loudness of speech sounds of the same length, stress, and pitch. Children with cochlear implants (CIs), with restored audibility and relatively intact temporal processing, are expected to benefit from the perceptual prominence cues of highly sonorous sounds. Sonority also influences lexical access through the sonority-sequencing principle (SSP), a grammatical phonotactic rule, which facilitates the recognition and segmentation of syllables within speech. The more nonsonorous the onset of a syllable is, the larger is the degree of sonority rise to the nucleus, and the more optimal the SSP. Children with CIs may experience hindered or delayed development of the language-learning rule SSP, as a result of their deprived/degraded auditory experience. The purpose of the study was to explore sonority's role in speech perception and lexical access of prelingually deafened children with CIs.

DESIGN

A case-control study with 15 children with CIs, 25 normal-hearing children (NHC), and 50 normal-hearing adults was conducted, using a lexical identification task of novel, nonreal CV-CV words taught via fast mapping. The CV-CV words were constructed according to four sonority conditions, entailing syllables with sonorous onsets/less optimal SSP (SS) and nonsonorous onsets/optimal SSP (NS) in all combinations, that is, SS-SS, SS-NS, NS-SS, and NS-NS. Outcome measures were accuracy and reaction times (RTs). A subgroup analysis of 12 children with CIs pair matched to 12 NHC on hearing age aimed to study the effect of oral-language exposure period on the sonority-related performance.

RESULTS

The children groups showed similar accuracy performance, overall and across all the sonority conditions. However, within-group comparisons showed that the children with CIs scored more accurately on the SS-SS condition relative to the NS-NS and NS-SS conditions, while the NHC performed equally well across all conditions. Additionally, adult-comparable accuracy performance was achieved by the children with CIs only on the SS-SS condition, as opposed to NS-SS, SS-NS, and SS-SS conditions for NHC. Accuracy analysis of the subgroups of children matched in hearing age showed similar results. Overall longer RTs were recorded by the children with CIs on the sonority-treated lexical task, specifically on the SS-SS condition compared with age-matched controls. However, the subgroup analysis showed that both groups of children did not differ on RTs.

CONCLUSIONS

Children with CIs performed better in lexical tasks relying on the sonority perceptual prominence cues, as in SS-SS condition, than on SSP initial relying conditions as NS-NS and NS-SS. Template-driven word learning, an early word-learning strategy, appears to play a role in the lexical access of children with CIs whether matched in hearing age or not. The SS-SS condition acts as a preferred word template. The longer RTs brought about by the highly accurate SS-SS condition in children with CIs is possibly because listening becomes more effortful. The lack of RTs difference between the children groups when matched on hearing age points out the importance of oral-language exposure period as a key factor in developing the auditory processing skills.

A Developmental Perspective on Processing Semantic Context: Preliminary Evidence from Sentential Auditory Word Repetition in School-Aged Children

The current investigation examined the developmental changes involved in processing semantic context in auditorily presented sentences, as well as underlying attentional and suppression mechanisms. Thirty-nine typically developing school-aged children aged 6;0-14;0 years participated in the current cross-sectional sentential auditory word repetition study. Component processes involved in auditory word recognition were examined and their respective developmental trajectories systematically delineated. Experimental manipulations included semantic congruity (congruous, incongruous), sentence constraint (high, low), cloze probability (high, low), and processing mode. High sentence constraints elicited top-down pre-potency type effects, which resulted in active suppression of anticipated cloze words and longer naming latencies of perceived cloze words when violated with conflicting bottom-up information. In addition, developmental changes in component processes reflected underlying changes in attention, with evidence that suppression mechanisms remained relatively constant with age. Findings are interpreted in line with the Trace (McClelland and Elman in Cogn Psychol 18(1):1-86, 1986) model of auditory word recognition.

Waiting for lexical access: Cochlear implants or severely degraded input lead listeners to process speech less incrementally

Spoken language unfolds over time. Consequently, there are brief periods of ambiguity, when incomplete input can match many possible words. Typical listeners solve this problem by immediately activating multiple candidates which compete for recognition. In two experiments using the visual world paradigm, we examined real-time lexical competition in prelingually deaf cochlear implant (CI) users, and normal hearing (NH) adults listening to severely degraded speech. In Experiment 1, adolescent CI users and NH controls matched spoken words to arrays of pictures including pictures of the target word and phonological competitors. Eye-movements to each referent were monitored asa measure of how strongly that candidate was considered over time. Relative to NH controls, CI users showed a large delay in fixating any object, less competition from onset competitors (e.g., sandwich after hearing sandal), and increased competition from rhyme competitors (e.g., candle after hearing sandal). Experiment 2 observed the same pattern with NH listeners hearing highly degraded speech. These studies suggests that in contrast to all prior studies of word recognition in typical listeners, listeners recognizing words in severely degraded conditions can exhibit a substantively different pattern of dynamics, waiting to begin lexical access until substantial information has accumulated.

Word segmentation from noise-band vocoded speech

Spectral degradation reduces access to the acoustics of spoken language and compromises how learners break into its structure. We hypothesised that spectral degradation disrupts word segmentation, but that listeners can exploit other cues to restore detection of words. Normal-hearing adults were familiarised to artificial speech that was unprocessed or spectrally degraded by noise-band vocoding into 16 or 8 spectral channels. The monotonic speech stream was pause-free (Experiment 1), interspersed with isolated words (Experiment 2), or slowed by 33% (Experiment 3). Participants were tested on segmentation of familiar vs. novel syllable sequences and on recognition of individual syllables. As expected, vocoding hindered both word segmentation and syllable recognition. The addition of isolated words, but not slowed speech, improved segmentation. We conclude that syllable recognition is necessary but not sufficient for successful word segmentation, and that isolated words can facilitate listeners' access to the structure of acoustically degraded speech.

The Effect of Word Frequency on Phonemic Accuracy in Children With Cochlear Implants and Peers With Typical Levels of Hearing

The frequency of occurrence of words and sounds has a pervasive influence on typically developing children's language acquisition. For instance, highly frequent words appear earliest in a child's lexicon, and highly frequent phonemes are produced more accurately. This study evaluates (a) whether word frequency influences word accuracy and (b) whether this is also the case for children with a history of auditory deprivation. More specifically, the influence of word frequency on phonemic accuracy is examined in deaf children with a cochlear implant (CI), and compared to age-matched children with typical hearing, between word onset and age 7. Results show that highly frequent words are produced more accurately, except for words in the highest frequency regions (i.e., predominantly closed-class words). This effect is more pronounced in children with typical hearing when compared with children with CI. Thus, children with CI are sensitive to word frequency, but to a lesser extent than peers with typical hearing.

Learning in Complex Environments: The Effects of Background Speech on Early Word Learning

Although most studies of language learning take place in quiet laboratory settings, everyday language learning occurs under noisy conditions. The current research investigated the effects of background speech on word learning. Both younger (22- to 24-month-olds; n = 40) and older (28- to 30-month-olds; n = 40) toddlers successfully learned novel label-object pairings when target speech was 10 dB louder than background speech but not when the signal-to-noise ratio (SNR) was 5 dB. Toddlers (28- to 30-month-olds; n = 26) successfully learned novel words with a 5-dB SNR when they initially heard the labels embedded in fluent speech without background noise, before they were mapped to objects. The results point to both challenges and protective factors that may impact language learning in complex auditory environments.

Current trends in outcome studies for children with hearing loss and the need to establish a comprehensive framework of measuring outcomes in children with hearing loss in China

Since the 1970s, outcome studies for children with hearing loss expanded from focusing on assessing auditory awareness and speech perception skills to evaluating language and speech development. Since the early 2000s, the multi-center large scale research systematically studied outcomes in the areas of auditory awareness, speech-perception, language development, speech development, educational achievements, cognitive development, and psychosocial development. These studies advocated the establishment of baseline and regular follow-up evaluations with a comprehensive framework centered on language development. Recent research interests also include understanding the vast differences in outcomes for children with hearing loss, understanding the relationships between neurocognitive development and language acquisition in children with hearing loss, and using outcome studies to guide evidence-based clinical practice. After the establishment of standardized Mandarin language assessments, outcomes research in Mainland China has the potential to expand beyond auditory awareness and speech perception studies.

An Open Conversation on Using Eye-Gaze Methods in Studies of Neurodevelopmental Disorders

PURPOSE

Eye-gaze methods have the potential to advance the study of neurodevelopmental disorders. Despite their increasing use, challenges arise in using these methods with individuals with neurodevelopmental disorders and in reporting sufficient methodological detail such that the resulting research is replicable and interpretable.

METHOD

This tutorial presents key considerations involved in designing and conducting eye-gaze studies for individuals with neurodevelopmental disorders and proposes conventions for reporting the results of such studies.

RESULTS

Methodological decisions (e.g., whether to use automated eye tracking or manual coding, implementing strategies to scaffold children's performance, defining valid trials) have cascading effects on the conclusions drawn from eye-gaze data. Research reports that include specific information about procedures, missing data, and selection of participants will facilitate interpretation and replication.

CONCLUSIONS

Eye-gaze methods provide exciting opportunities for studying neurodevelopmental disorders. Open discussion of the issues presented in this tutorial will improve the pace of productivity and the impact of advances in research on neurodevelopmental disorders.

Are Young Children With Cochlear Implants Sensitive to the Statistics of Words in the Ambient Spoken Language?

PURPOSE

The purpose of this study was to determine whether children with cochlear implants (CIs) are sensitive to statistical characteristics of words in the ambient spoken language, whether that sensitivity changes in expected ways as their spoken lexicon grows, and whether that sensitivity varies with unilateral or bilateral implantation.

METHOD

We analyzed archival data collected from the parents of 36 children who received cochlear implantation (20 unilateral, 16 bilateral) before 24 months of age. The parents reported their children's word productions 12 months after implantation using the MacArthur Communicative Development Inventories: Words and Sentences (Fenson et al., 1993). We computed the number of words, out of 292 possible monosyllabic nouns, verbs, and adjectives, that each child was reported to say and calculated the average phonotactic probability, neighborhood density, and word frequency of the reported words.

RESULTS

Spoken vocabulary size positively correlated with average phonotactic probability and negatively correlated with average neighborhood density, but only in children with bilateral CIs.

CONCLUSION

At 12 months postimplantation, children with bilateral CIs demonstrate sensitivity to statistical characteristics of words in the ambient spoken language akin to that reported for children with normal hearing during the early stages of lexical development. Children with unilateral CIs do not.

Brazilian adaptation of the Functioning after Pediatric Cochlear Implantation (FAPCI): comparison between normal hearing and cochlear implanted children

OBJECTIVE

Enabling development of the ability to communicate effectively is the principal objective of cochlear implantation (CI) in children. However, objective and effective metrics of communication for cochlear-implanted Brazilian children are lacking. The Functioning after Pediatric Cochlear Implantation (FAPCI), a parent/caregiver reporting instrument developed in the United States, is the first communicative performance scale for evaluation of real-world verbal communicative performance of 2-5-year-old children with cochlear implants. The primary aim was to cross-culturally adapt and validate the Brazilian-Portuguese version of the FAPCI. The secondary aim was to conduct a trial of the adapted Brazilian-Portuguese FAPCI (FAPCI-BP) in normal hearing (NH) and CI children.

METHODS

The American-English FAPCI was translated by a rigorous forward-backward process. The FAPCI-BP was then applied to the parents of children with NH (n=131) and CI (n=13), 2-9 years of age. Test-retest reliability was verified.

RESULTS

The FAPCI-BP was confirmed to have excellent internal consistency (Cronbach's alpha > 0.90). The CI group had lower FAPCI scores (58.38 ± 22.6) than the NH group (100.38 ± 15.2; p<0.001, Wilcoxon test).

CONCLUSION

The present results indicate that the FAPCI-BP is a reliable instrument. It can be used to evaluate verbal communicative performance in children with and without CI. The FAPCI is currently the only psychometrically-validated instrument that allows such measures in cochlear-implanted children.

Deaf children with cochlear implants do not appear to use sentence context to help recognize spoken words

PURPOSE

The authors investigated the ability of deaf children with cochlear implants (CIs) to use sentence context to facilitate the perception of spoken words.

METHOD

Deaf children with CIs (n = 24) and an age-matched group of children with normal hearing (n = 31) were presented with lexically controlled sentences and were asked to repeat each sentence in its entirety. Performance was analyzed at each of 3 word positions of each sentence (first, second, and third key word).

RESULTS

Whereas the children with normal hearing showed robust effects of contextual facilitation-improved speech perception for the final words in a sentence-the deaf children with CIs on average showed no such facilitation. Regression analyses indicated that for the deaf children with CIs, Forward Digit Span scores significantly predicted accuracy scores for all 3 positions, whereas performance on the Stroop Color and Word Test, Children's Version (Golden, Freshwater, & Golden, 2003) predicted how much contextual facilitation was observed at the final word.

CONCLUSIONS

The pattern of results suggests that some deaf children with CIs do not use sentence context to improve spoken word recognition. The inability to use sentence context may be due to possible interactions between language experience and cognitive factors that affect the ability to successfully integrate temporal-sequential information in spoken language.

Toddlers' ability to map the meaning of new words in multi-talker environments

Whether in a noisy daycare center, home, or classroom, many of the environments children are exposed to are, undoubtedly, not acoustically ideal for speech processing. Yet, somehow, these toddlers are still able to acquire vocabularies consisting of hundreds of words. The current study explores the effect of background speech noise on children's early word learning (specifically, their ability to map a label onto an object). Three groups of children aged 32-36 months were taught two new words either in quiet, or in the presence of multi-talker babble at a +5 or 0 dB signal-to-noise ratio (SNR). They were then tested on their learning of these new word-to-object mappings. Children showed similar accuracy in all three conditions, suggesting that even at a 0 dB SNR, children were successfully able to learn new words.

Processing of phonological variation in children with hearing loss: compensation for English place assimilation in connected speech

PURPOSE

In this study, the authors explored phonological processing in connected speech in children with hearing loss. Specifically, the authors investigated these children's sensitivity to English place assimilation, by which alveolar consonants like t and n can adapt to following sounds (e.g., the word ten can be realized as tem in the phrase ten pounds).

METHOD

Twenty-seven 4- to 8-year-old children with moderate to profound hearing impairments, using hearing aids (n = 10) or cochlear implants (n = 17), and 19 children with normal hearing participated. They were asked to choose between pictures of familiar (e.g., pen) and unfamiliar objects (e.g., astrolabe) after hearing t- and n-final words in sentences. Standard pronunciations (Can you find the pen dear?) and assimilated forms in correct (… pem please?) and incorrect contexts (… pem dear?) were presented.

RESULTS

As expected, the children with normal hearing chose the familiar object more often for standard forms and correct assimilations than for incorrect assimilations. Thus, they are sensitive to word-final place changes and compensate for assimilation. However, the children with hearing impairment demonstrated reduced sensitivity to word-final place changes, and no compensation for assimilation. Restricted analyses revealed that children with hearing aids who showed good perceptual skills compensated for assimilation in plosives only.

Bilateral cochlear implantation in children: a systematic review and best-evidence synthesis

OBJECTIVES/HYPOTHESIS

To evaluate the effectiveness of bilateral cochlear implantation over unilateral implantation in children with sensorineural hearing loss.

DATA SOURCES

Pubmed, Embase, and Web of Science.

REVIEW METHODS

All studies comparing a bilateral cochlear implant group with a unilateral implant group were included.

RESULTS

Twenty-one studies compared a bilateral cochlear implant group with a unilateral group. No randomized trials were identified. Due to the clinical heterogeneity, statistical pooling was not feasible and a best-evidence synthesis was performed. The results of this best-evidence synthesis indicate the positive effect of the second implant for especially sound localization and possibly for preverbal communication and language development. There was insufficient evidence to make a valid comparison between bilateral implantation and a bimodal fitting.

CONCLUSION

Although randomized trials are lacking, the results of our best-evidence synthesis indicate that the second cochlear implant might be especially useful in sound localization and possibly also in language development.

Reaching for sound measures: an ecologically valid estimate of spatial hearing in 2- to 3-year-old children with bilateral cochlear implants

HYPOTHESIS

A novel reaching for sound (RFS) methodology can yield a high level of spatial hearing ability in 2- to 3-year-old children with normal hearing and with bilateral cochlear implants (BiCIs).

BACKGROUND

A growing number of children who are deaf are receiving BiCIs at a young age. Their spatial hearing abilities are emerging but highly variable within the population. Our novel reaching for sound method uses an ecologically valid approach that engages children and maintains their motivation. The present work was aimed at using the novel RFS method to evaluate spatial hearing in 2- to 3-year-olds with normal hearing and with BiCIs.

METHODS

Six children with BiCIs and 15 children with NH, ages 2 to 3 years participated. In the BiCI group, testing was performed in bilateral or single CI (unilateral) conditions. Loudspeakers were separated by ± 60, ± 45, ± 30, or ± 15 degrees. On each trial, a small toy was hidden behind one of the loudspeakers, and the child's task was to reach through a hole in the curtain above the loudspeaker, to indicate source location. Children were reinforced for correct responses. At each angle, the ability of the child to reach criterion of 80% or greater correct was assessed.

RESULTS

All BiCI users reached criterion at all angles tested in the bilateral condition; however, performance was poorer when using a single CI. Of the 15 NH children, 13 were able to perform the task accurately and reached criterion at all angles.

CONCLUSION

Spatial hearing skills studied with the RFS method revealed novel findings regarding the emergence of sound localization in very young BiCI users.

Individual differences in the real-time comprehension of children with ASD

Many children with autism spectrum disorders (ASD) demonstrate deficits in language comprehension, but little is known about how they process spoken language as it unfolds. Real-time lexical comprehension is associated with language and cognition in children without ASD, suggesting that this may also be the case for children with ASD. This study adopted an individual differences approach to characterizing real-time comprehension of familiar words in a group of 34 three- to six-year-olds with ASD. The looking-while-listening paradigm was employed; it measures online accuracy and latency through language-mediated eye movements and has limited task demands. On average, children demonstrated comprehension of the familiar words, but considerable variability emerged. Children with better accuracy were faster to process the familiar words. In combination, processing speed and comprehension on a standardized language assessment explained 63% of the variance in online accuracy. Online accuracy was not correlated with autism severity or maternal education, and nonverbal cognition did not explain unique variance. Notably, online accuracy at age 5½ was related to vocabulary comprehension 3 years earlier. The words typically learned earliest in life were processed most quickly. Consistent with a dimensional view of language abilities, these findings point to similarities in patterns of language acquisition in typically developing children and those with ASD. Overall, our results emphasize the value of examining individual differences in real-time language comprehension in this population. We propose that the looking-while-listening paradigm is a sensitive and valuable methodological tool that can be applied across many areas of autism research.

Phonetic processing during the acquisition of new words in 3-to-6-year-old French-speaking deaf children with cochlear implants

The present study explores phonetic processing in deaf children with cochlear implants (CIs) when they have to learn phonetically similar words. Forty-six 34-to-78-month-old French-speaking deaf children with CIs were tested on 16 different trials. In each trial, they were first trained with two word-object pairings, and then a third object was presented and labeled with one of the familiar words. Children were asked to match one of the previously labeled objects with the third (same-labeled) object. Each pair of words contrasted on either the initial consonant or the first vowel by one or several phonetic features. The results show that deaf children with CIs are able to establish a new referential link between a word and an object. However, their performance is lower than that previously observed in normal-hearing children (NH). In such a situation, they process contrasts involving several phonetic features correctly, but show difficulties with minimal contrasts. The ability to recruit fine phonetic sensitivity during word learning appears to be influenced mainly by duration of implant use, with an overall increase of performance during the 3 years after implantation. There was no chronological age effect, nor age at implantation effect on the quality of processing. Difficulty with minimal contrasts and the absence of any age at implantation effects in this age range are discussed in light of recent studies on lexical development.

LEARNING OUTCOMES

After reading this article, the reader will be able to recognize the perceptual skills of children with cochlear implants and distinguish those perceptual features that are difficult for the children to perceive.

Spatial acuity in 2-to-3-year-old children with normal acoustic hearing, unilateral cochlear implants, and bilateral cochlear implants

OBJECTIVES

: To measure spatial acuity on a right-left discrimination task in 2-to-3-year-old children who use a unilateral cochlear implant (UCI) or bilateral cochlear implants (BICIs); to test the hypothesis that BICI users perform significantly better when they use two CIs than when using a single CI, and that they perform better than the children in the UCI group; to determine how well children with CIs perform compared with children who have normal acoustic hearing (NH); to determine the effect of intensity roving on spatial acuity.

DESIGN

: Three groups of children between 26 and 36 months of age participated in this study: 8 children with NH (mean age: 30.9 months), 12 children who use a UCI (mean age: 31.9 months), and 27 children who use BICIs (mean age: 30.7 months). Testing was conducted in a large sound-treated booth with loudspeakers positioned in a horizontal arc with a radius of 1.2 m. The observer-based psychophysical procedure was used to measure the children's ability to identify the hemifield containing the sound source (right versus left). Two methods were used for quantifying spatial acuity, an adaptive-tracking method and a fixed-angle method. In Experiment 1 an adaptive tracking algorithm was used to vary source angle, and the minimum audible angle (MAA), the smallest angle at which right-left discrimination performance is better than chance, was estimated. All three groups participated in Experiment 1. In Experiment 2 source angles were fixed at ±50 degrees, and performance was evaluated by computing the number of SDs above chance. Children in the UCI and BICI groups participated in Experiment 2.

RESULTS

: In Experiment 1, when stimulus intensity was roved by 8 dB, MAA thresholds were 3.3 degrees to 30.2 degrees (mean = 14.5 degrees) and 5.7 degrees to 69.6 degrees (mean = 30.9 degrees) in the NH group and in the BICI group, respectively. When the intensity level was fixed for the BICI group, performance did not improve. Within the BICI group, 5 out of 27 children obtained MAA thresholds within one SD of their peers who have NH; all five had >12 months of bilateral listening experience. In Experiment 2, BICIs provided some advantages when the intensity level was fixed. First, the BICI group outperformed the UCI group. Second, children in the BICI group who repeated the task with their 1st CI alone had statistically significantly better performance when using both devices. In addition, when intensity roving was introduced, a larger percentage of children who had 12 or more months of BICI experience continued to perform above chance than children who had <12 months of BICI experience. Taken together, the results suggest that children with BICIs have spatial acuity that is better than when using their first CI alone and than that of their peers who use UCIs. In addition, longer durations of BICI use tend to result in better performance, although this cannot be generalized to all participants.

CONCLUSION

: This report is consistent with a growing body of evidence that spatial-hearing skills can emerge in young children who use BICIs. The observation that these skills are not concomitantly emerging in age- and experience-matched children who use UCIs suggests that BICIs provide cues that are necessary for these spatial-hearing skills that UCIs do not provide.

Toddlers' recognition of noise-vocoded speech

Despite their remarkable clinical success, cochlear-implant listeners today still receive spectrally degraded information. Much research has examined normally hearing adult listeners' ability to interpret spectrally degraded signals, primarily using noise-vocoded speech to simulate cochlear implant processing. Far less research has explored infants' and toddlers' ability to interpret spectrally degraded signals, despite the fact that children in this age range are frequently implanted. This study examines 27-month-old typically developing toddlers' recognition of noise-vocoded speech in a language-guided looking study. Children saw two images on each trial and heard a voice instructing them to look at one item ("Find the cat!"). Full-spectrum sentences or their noise-vocoded versions were presented with varying numbers of spectral channels. Toddlers showed equivalent proportions of looking to the target object with full-speech and 24- or 8-channel noise-vocoded speech; they failed to look appropriately with 2-channel noise-vocoded speech and showed variable performance with 4-channel noise-vocoded speech. Despite accurate looking performance for speech with at least eight channels, children were slower to respond appropriately as the number of channels decreased. These results indicate that 2-yr-olds have developed the ability to interpret vocoded speech, even without practice, but that doing so requires additional processing. These findings have important implications for pediatric cochlear implantation.

Studies on bilateral cochlear implants at the University of Wisconsin's Binaural Hearing and Speech Laboratory

This report highlights research projects relevant to binaural and spatial hearing in adults and children. In the past decade we have made progress in understanding the impact of bilateral cochlear implants (BiCIs) on performance in adults and children. However, BiCI users typically do not perform as well as normal hearing (NH) listeners. In this article we describe the benefits from BiCIs compared with a single cochlear implant (CI), focusing on measures of spatial hearing and speech understanding in noise. We highlight the fact that in BiCI listening the devices in the two ears are not coordinated; thus binaural spatial cues that are available to NH listeners are not available to BiCI users. Through the use of research processors that carefully control the stimulus delivered to each electrode in each ear, we are able to preserve binaural cues and deliver them with fidelity to BiCI users. Results from those studies are discussed as well, with a focus on the effect of age at onset of deafness and plasticity of binaural sensitivity. Our work with children has expanded both in number of subjects tested and age range included. We have now tested dozens of children ranging in age from 2 to 14 yr. Our findings suggest that spatial hearing abilities emerge with bilateral experience. While we originally focused on studying performance in free field, where real world listening experiments are conducted, more recently we have begun to conduct studies under carefully controlled binaural stimulation conditions with children as well. We have also studied language acquisition and speech perception and production in young CI users. Finally, a running theme of this research program is the systematic investigation of the numerous factors that contribute to spatial and binaural hearing in BiCI users. By using CI simulations (with vocoders) and studying NH listeners under degraded listening conditions, we are able to tease apart limitations due to the hardware/software of the CI systems from limitations due to neural pathology.

Production of contrast between sibilant fricatives by children with cochlear implants

Speech production by children with cochlear implants (CIs) is generally less intelligible and less accurate on a phonemic level than that of normally hearing children. Research has reported that children with CIs produce less acoustic contrast between phonemes than normally hearing children, but these studies have included correct and incorrect productions. The present study compared the extent of contrast between correct productions of /s/ and /∫/ by children with CIs and two comparison groups: (1) normally hearing children of the same chronological age as the children with CIs and (2) normally hearing children with the same duration of auditory experience. Spectral peaks and means were calculated from the frication noise of productions of /s/ and /∫/. Results showed that the children with CIs produced less contrast between /s/ and /∫/ than normally hearing children of the same chronological age and normally hearing children with the same duration of auditory experience due to production of /s/ with spectral peaks and means at lower frequencies. The results indicate that there may be differences between the speech sounds produced by children with CIs and their normally hearing peers even for sounds that adults judge as correct.

Measuring communicative performance with the FAPCI instrument: preliminary results from normal hearing and cochlear implanted children

OBJECTIVE

To develop preliminary "growth curves" of Functioning after Pediatric Cochlear Implantation (FAPCI) scores using a cross-sectional sample of normal hearing children and to compare these curves to trajectories of FAPCI scores in children receiving cochlear implants.

METHODS

Quantile regression was used to develop growth curves from the FAPCI scores of a cross-sectional sample of 82 normal hearing children (age range 7 months-5 years). Trajectories of FAPCI scores from a longitudinal cohort of 75 children with cochlear implants (age range 1-5 years) were compared to these growth curves.

RESULTS

FAPCI scores were positively associated with increasing age in normal hearing children with a rapid increase in scores observed at earlier ages followed by a plateau at age 3 years. FAPCI trajectories for cochlear-implanted children varied with age at implantation and did not reach a plateau until age 5-6 years.

CONCLUSION

Normal hearing children demonstrated increasing FAPCI scores with age, and these preliminary growth curves allow for the interpretation of a cochlear-implanted child's FAPCI scores in comparison to normal hearing children. Additional research using a larger, longitudinal cohort of normal hearing children will be needed to develop definitive normative FAPCI trajectories.