Phonetic variation in consonants in infant-directed and adult-directed speech: the case of regressive place assimilation in word-final alveolar stops.

Pronunciation variation is under-studied in infant-directed speech, particularly for consonants. Regressive place assimilation involves a word-final alveolar stop taking the place of articulation of a following word-initial consonant. We investigated pronunciation variation in word-final alveolar stop consonants in storybooks read by forty-eight mothers in adult-directed or infant-directed style to infants aged approximately 0;3, 0;9, 1;1, or 1;8. We focused on phonological environments where regressive place assimilation could occur, i.e., when the stop preceded a word-initial labial or velar consonant. Spectrogram, waveform, and perceptual evidence was used to classify tokens into four pronunciation categories: canonical, assimilated, glottalized, or deleted. Results showed a reliable tendency for canonical variants to occur in infant-directed speech more often than in adult-directed speech. However, the otherwise very similar distributions of variants across addressee and age group suggested that infants largely experience statistical distributions of non-canonical consonantal pronunciation variants that mirror those experienced by adults.

Hearing versus Listening: Attention to Speech and Its Role in Language Acquisition in Deaf Infants with Cochlear Implants.

The advent of cochlear implantation has provided thousands of deaf infants and children access to speech and the opportunity to learn spoken language. Whether or not deaf infants successfully learn spoken language after implantation may depend in part on the extent to which they listen to speech rather than just hear it. We explore this question by examining the role that attention to speech plays in early language development according to a prominent model of infant speech perception - Jusczyk's WRAPSA model - and by reviewing the kinds of speech input that maintains normal-hearing infants' attention. We then review recent findings suggesting that cochlear-implanted infants' attention to speech is reduced compared to normal-hearing infants and that speech input to these infants differs from input to infants with normal hearing. Finally, we discuss possible roles attention to speech may play on deaf children's language acquisition after cochlear implantation in light of these findings and predictions from Jusczyk's WRAPSA model.

Effects of deafness on acoustic characteristics of American English tense/lax vowels in maternal speech to infants.

Recent studies have demonstrated that mothers exaggerate phonetic properties of infant-directed (ID) speech. However, these studies focused on a single acoustic dimension (frequency), whereas speech sounds are composed of multiple acoustic cues. Moreover, little is known about how mothers adjust phonetic properties of speech to children with hearing loss. This study examined mothers' production of frequency and duration cues to the American English tense/lax vowel contrast in speech to profoundly deaf (N = 14) and normal-hearing (N = 14) infants, and to an adult experimenter. First and second formant frequencies and vowel duration of tense (/i/, /u/) and lax (/I/, /ʊ/) vowels were measured. Results demonstrated that for both infant groups mothers hyperarticulated the acoustic vowel space and increased vowel duration in ID speech relative to adult-directed speech. Mean F2 values were decreased for the /u/ vowel and increased for the /I/ vowel, and vowel duration was longer for the /i/, /u/, and /I/ vowels in ID speech. However, neither acoustic cue differed in speech to hearing-impaired or normal-hearing infants. These results suggest that both formant frequencies and vowel duration that differentiate American English tense/lx vowel contrasts are modified in ID speech regardless of the hearing status of the addressee.

The ear is connected to the brain: some new directions in the study of children with cochlear implants at Indiana University.

Since the early 1980s, the DeVault Otologic Research Laboratory at the Indiana University School of Medicine has been on the forefront of research on speech and language outcomes in children with cochlear implants. This paper highlights work over the last decade that has moved beyond collecting speech and language outcome measures to focus more on investigating the underlying cognitive, social, and linguistic skills that predict speech and language outcomes. This recent work reflects our growing appreciation that early auditory deprivation can affect more than hearing and speech perception. The new directions include research on attention to speech, word learning, phonological development, social development, and neurocognitive processes. We have also expanded our subject populations to include infants and children with additional disabilities.

The Effects of Individualized Music Listening on Affective, Behavioral, Cognitive, and Sundowning Symptoms of Dementia in Long-Term Care Residents.

OBJECTIVES: This study aimed to replicate music's positive effects on dementia-related symptoms, determine whether a 6-month intervention would lead to greater positive outcomes than typical 3- to 4-month interventions, and examine changes in sundowning symptoms after music listening. METHODS: 282 nursing home residents with dementia listened to personalized music playlists 1-3 times weekly for 30 minutes across 6 months. Standardized assessments of affect, behavior, and cognition and direct observations of sundowning symptoms comprised the outcomes. RESULTS: Results documented significant improvements in residents' general neuropsychiatric symptoms, agitation, and depression across the first 3 months, but no additional improvements across the subsequent 3 months. Seven sundowning symptoms significantly improved following music listening, with some (e.g., disengagement) being more amenable to music than others (e.g., aggression). DISCUSSION: Results support short-term individualized music listening as an effective non-pharmacological approach for improving dementia-related symptoms in nursing home residents and suggest new applications of music-related interventions.

Nursing Home Residents' Positive Behavioral Responses to Individualized Music Predict Improvements in Sundowning Symptoms After Music Listening.

Objective: The goal of this exploratory study was to predict which long-term care residents with dementia would experience improvements in their sundowning symptoms after listening to personalized music playlists. Methods: We studied 101 residents with moderate to severe dementia from 15 long-term care facilities across 8 months. We observed residents' behavioral responses to individualized music while they listened and recorded sundowning symptoms both before and after each listening session. Results: As hypothesized, residents who exhibited a greater number of positive reactive behaviors while listening to music also evidenced more improvements in their confusion, disengagement, unresponsiveness, and restlessness after their music-listening session. Discussion: Our results reveal that observing behavioral responses during music listening is an effective way to determine when nursing home residents are benefiting from personalized music playlists. These findings inform music programs in long-term care settings by identifying residents whose sundowning symptoms are most amenable to music intervention.

Lexical Repetition Properties of Caregiver Speech and Language Development in Children With Cochlear Implants.

Purpose Early language input plays an important role in child language and cognitive development (e.g., Gilkerson et al., 2018; Hart & Risley, 1995). In this study, we examined the effects of child's hearing status on lexical repetition properties of speech produced by their caregivers with normal hearing (NH). In addition, we investigated the relationship between maternal lexical repetition properties and later language skills in English-learning infants with cochlear implants (CIs). Method In a free-play session, 17 mothers and their prelingually deaf infants who received CIs before 2 years of age (CI group) were recorded at two post-CI intervals: 3 and 6 months postactivation; 18 hearing experience-matched infants with NH and their mothers and 14 chronological age-matched infants with NH group and their mothers were matched to the CI group. Maternal speech was transcribed from the recordings, and measures of maternal lexical repetition were obtained. Standardized language assessments were administered on children with CIs approximately two years after CI activation. Results The findings indicated that measures of lexical repetition were similar among the three groups of mothers, regardless of the hearing status of their infants. In addition, lexical repetition measures were correlated with later language skills in infants with CIs. Conclusions Infants with CIs receive the language input that contains similar lexical repetition properties as that in the speech received by their peers with NH, which is likely to play an important role in child speech processing and language development. These findings provide the knowledge for professionals to coach parents to implement specific language intervention strategies to support language development in infants with hearing loss. Supplemental Material https://doi.org/10.23641/asha.11936322.

Statistical distributions of consonant variants in infant-directed speech: evidence that /t/ may be exceptional.

Statistical distributions of phonetic variants in spoken language influence speech perception for both language learners and mature users. We theorized that patterns of phonetic variant processing of consonants demonstrated by adults might stem in part from patterns of early exposure to statistics of phonetic variants in infant-directed (ID) speech. In particular, we hypothesized that ID speech might involve greater proportions of canonical /t/ pronunciations compared to adult-directed (AD) speech in at least some phonological contexts. This possibility was tested using a corpus of spontaneous speech of mothers speaking to other adults, or to their typically-developing infant. Tokens of word-final alveolar stops - including /t/, /d/, and the nasal stop /n/ - were examined in assimilable contexts (i.e., those followed by a word-initial labial and/or velar); these were classified as canonical, assimilated, deleted, or glottalized. Results confirmed that there were significantly more canonical pronunciations in assimilable contexts in ID compared with AD speech, an effect which was driven by the phoneme /t/. These findings suggest that at least in phonological contexts involving possible assimilation, children are exposed to more canonical /t/ variant pronunciations than adults are. This raises the possibility that perceptual processing of canonical /t/ may be partly attributable to exposure to canonical /t/ variants in ID speech. Results support the need for further research into how statistics of variant pronunciations in early language input may shape speech processing across the lifespan.

Preference for Infant-Directed Speech in Infants With Hearing Aids: Effects of Early Auditory Experience.

Purpose: It is well established that (a) infants prefer listening to infant-directed speech (IDS) over adult-directed speech (ADS), and (b) IDS facilitates speech, language, and cognitive development, compared with ADS. The main purpose of this study was to determine whether infants with hearing aids (HAs), similar to their peers with normal hearing (NH), show a listening preference for IDS over ADS. Method: A total of 42 infants participated in the study. In Experiment 1, 9 infants with hearing loss, who had approximately 12 months of experience (mean chronological age of 17.57 months) with HAs, and 9 infants with NH, who had similar chronological age (17.54 months), were tested. In Experiment 2, 10 infants with hearing loss, who had approximately 4 months of experience (mean chronological age of 9.86 months) with HAs, and 14 infants with NH, who had similar chronological age (9.09 months), were tested. Infants were tested on their listening preference in 3 randomized blocks: IDS versus silence, ADS versus silence, and IDS versus ADS blocks, using the central fixation preference procedure. Results: Experiment 1 showed that infants with HAs, similar to their peers with NH, listened longer to both IDS and ADS relative to silence; however, neither infants with HAs nor infants with NH showed a listening preference for IDS over ADS. In Experiment 2, both infants with HAs and infants with NH showed a listening preference for IDS and ADS relative to silence; in addition, both groups preferred listening to IDS over ADS. Conclusions: Infants with HAs appear to have sufficient access to the acoustic cues in the speech that allow them to develop an age-equivalent IDS preference. This may be attributed to a combination of being able to use the hearing they do have before receiving HAs and early device fitting. Given previously demonstrated positive associations between IDS preference and language development, this research encourages early interventions focusing on maximizing early auditory experience in infants with hearing loss. Supplemental Material: https://doi.org/10.23641/asha.6906365.

Infant-Directed Speech Enhances Attention to Speech in Deaf Infants With Cochlear Implants.

Purpose: Both theoretical models of infant language acquisition and empirical studies posit important roles for attention to speech in early language development. However, deaf infants with cochlear implants (CIs) show reduced attention to speech as compared with their peers with normal hearing (NH; Horn, Davis, Pisoni, & Miyamoto, 2005; Houston, Pisoni, Kirk, Ying, & Miyamoto, 2003), which may affect their acquisition of spoken language. The main purpose of this study was to determine (a) whether infant-directed speech (IDS) enhances attention to speech in infants with CIs, as compared with adult-directed speech (ADS), and (b) whether the degree to which infants with CIs pay attention to IDS is associated with later language outcomes. Method: We tested 46 infants-12 prelingually deaf infants who received CIs before 24 months of age and had 12 months of hearing experience (CI group), 22 hearing experience-matched infants with NH (NH-HEM group), and 12 chronological age-matched infants with NH (NH-CAM group)-on their listening preference in 3 randomized blocks: IDS versus silence, ADS versus silence, and IDS versus ADS. We administered the Preschool Language Scale-Fourth Edition (PLS-4; Zimmerman, Steiner, & Pond, 2002) approximately 18 months after implantation to assess receptive and expressive language skills of infants with CIs. Results: In the IDS versus silence block, all 3 groups looked significantly longer to IDS than to silence. In the ADS versus silence block, both the NH-HEM and NH-CAM groups looked significantly longer to ADS relative to silence; however, the CI group did not show any preference. In the IDS versus ADS block, whereas both the CI and NH-HEM groups preferred IDS over ADS, the NH-CAM group looked equally long to IDS and ADS. IDS preference quotient among infants with CIs in the IDS versus ADS block was associated with PLS-4 Auditory Comprehension and PLS-4 Expressive Communication measures. Conclusions: Two major findings emerge: (a) IDS enhances attention to speech in deaf infants with CIs; (b) the degree of IDS preference over ADS relates to language development in infants with CIs. These results support a focus on input in developing intervention strategies to mitigate the effects of hearing loss on language development in infants with hearing loss.

Contribution of hearing aids to music perception by cochlear implant users.

OBJECTIVES: Modern cochlear implant (CI) encoding strategies represent the temporal envelope of sounds well but provide limited spectral information. This deficit in spectral information has been implicated as a contributing factor to difficulty with speech perception in noisy conditions, discriminating between talkers and melody recognition. One way to supplement spectral information for CI users is by fitting a hearing aid (HA) to the non-implanted ear. METHODS: In this study 14 postlingually deaf adults (half with a unilateral CI and the other half with a CI and an HA (CI + HA)) were tested on measures of music perception and familiar melody recognition. RESULTS: CI + HA listeners performed significantly better than CI-only listeners on all pitch-based music perception tasks. The CI + HA group did not perform significantly better than the CI-only group in the two tasks that relied on duration cues. Recognition of familiar melodies was significantly enhanced for the group wearing an HA in addition to their CI. This advantage in melody recognition was increased when melodic sequences were presented with the addition of harmony. CONCLUSION: These results show that, for CI recipients with aidable hearing in the non-implanted ear, using a HA in addition to their implant improves perception of musical pitch and recognition of real-world melodies.

Affective Properties of Mothers' Speech to Infants With Hearing Impairment and Cochlear Implants.

PURPOSE: The affective properties of infant-directed speech influence the attention of infants with normal hearing to speech sounds. This study explored the affective quality of maternal speech to infants with hearing impairment (HI) during the 1st year after cochlear implantation as compared to speech to infants with normal hearing. METHOD: Mothers of infants with HI and mothers of infants with normal hearing matched by age (NH-AM) or hearing experience (NH-EM) were recorded playing with their infants during 3 sessions over a 12-month period. Speech samples of 25 s were low-pass filtered, leaving intonation but not speech information intact. Sixty adults rated the stimuli along 5 scales: positive/negative affect and intention to express affection, to encourage attention, to comfort/soothe, and to direct behavior. RESULTS: Low-pass filtered speech to HI and NH-EM groups was rated as more positive, affective, and comforting compared with the such speech to the NH-AM group. Speech to infants with HI and with NH-AM was rated as more directive than speech to the NH-EM group. Mothers decreased affective qualities in speech to all infants but increased directive qualities in speech to infants with NH-EM over time. CONCLUSIONS: Mothers fine-tune communicative intent in speech to their infant's developmental stage. They adjust affective qualities to infants' hearing experience rather than to chronological age but adjust directive qualities of speech to the chronological age of their infants.

Vowel space characteristics of speech directed to children with and without hearing loss.

PURPOSE: This study examined vowel characteristics in adult-directed (AD) and infant-directed (ID) speech to children with hearing impairment who received cochlear implants or hearing aids compared with speech to children with normal hearing. METHOD: Mothers' AD and ID speech to children with cochlear implants (Study 1, n=20) or hearing aids (Study 2, n=11) was compared with mothers' speech to controls matched on age and hearing experience. The first and second formants of vowels /i/, /ɑ/, and /u/ were measured, and vowel space area and dispersion were calculated. RESULTS: In both studies, vowel space was modified in ID compared with AD speech to children with and without hearing loss. Study 1 showed larger vowel space area and dispersion in ID compared with AD speech regardless of infant hearing status. The pattern of effects of ID and AD speech on vowel space characteristics in Study 2 was similar to that in Study 1, but depended partly on children's hearing status. CONCLUSION: Given previously demonstrated associations between expanded vowel space in ID compared with AD speech and enhanced speech perception skills, this research supports a focus on vowel pronunciation in developing intervention strategies for improving speech-language skills in children with hearing impairment.

Phonetic modification of vowel space in storybook speech to infants up to 2 years of age.

PURPOSE: A large body of literature has indicated vowel space area expansion in infant-directed (ID) speech compared with adult-directed (AD) speech, which may promote language acquisition. The current study tested whether this expansion occurs in storybook speech read to infants at various points during their first 2 years of life. METHOD: In 2 studies, mothers read a storybook containing target vowels in ID and AD speech conditions. Study 1 was longitudinal, with 11 mothers recorded when their infants were 3, 6, and 9 months old. Study 2 was cross-sectional, with 48 mothers recorded when their infants were 3, 9, 13, or 20 months old (n=12 per group). The 1st and 2nd formants of vowels /i/, /ɑ/, and /u/ were measured, and vowel space area and dispersion were calculated. RESULTS: Across both studies, 1st and/or 2nd formant frequencies shifted systematically for /i/ and /u/ vowels in ID compared with AD speech. No difference in vowel space area or dispersion was found. CONCLUSIONS: The results suggest that a variety of communication and situational factors may affect phonetic modifications in ID speech, but that vowel space characteristics in speech to infants stay consistent across the first 2 years of life.

A Longitudinal Study of Audiovisual Speech Perception by Children with Hearing Loss Who have Cochlear Implants.

The present study investigated the development of audiovisual speech perception skills in children who are prelingually deaf and received cochlear implants. We analyzed results from the Pediatric Speech Intelligibility (Jerger, Lewis, Hawkins, & Jerger, 1980) test of audiovisual spoken word and sentence recognition skills obtained from a large group of young children with cochlear implants enrolled in a longitudinal study, from pre-implantation to 3 years post-implantation. The results revealed better performance under the audiovisual presentation condition compared with auditory-alone and visual-alone conditions. Performance in all three conditions improved over time following implantation. The results also revealed differential effects of early sensory and linguistic experience. Children from oral communication (OC) education backgrounds performed better overall than children from total communication (TC backgrounds. Finally, children in the early-implanted group performed better than children in the late-implanted group in the auditory-alone presentation condition after 2 years of cochlear implant use, whereas children in the late-implanted group performed better than children in the early-implanted group in the visual-alone condition. The results of the present study suggest that measures of audiovisual speech perception may provide new methods to assess hearing, speech, and language development in young children with cochlear implants.

Synchrony, complexity and directiveness in mothers' interactions with infants pre- and post-cochlear implantation.

This study investigated effects of profound hearing loss on mother-infant interactions before and after cochlear implantation with a focus on maternal synchrony, complexity, and directiveness. Participants included two groups of mother-infant dyads: 9 dyads of mothers and infants with normal hearing; and 9 dyads of hearing mothers and infants with profound hearing loss. Dyads were observed at two time points: Time 1, scheduled to occur before cochlear implantation for infants with profound hearing loss (mean age=13.6 months); and Time 2 (mean age=23.3 months), scheduled to occur approximately six months after cochlear implantation. Hearing infants were age-matched to infants with hearing loss at both time points. Dependent variables included the proportion of maternal utterances that overlapped infant vocalizations, maternal mean length of utterance, infant word use, and combined maternal directives and prohibitions. Results showed mothers' utterances overlapped the vocalizations of infants with hearing loss more often before cochlear implantation than after, mothers used less complex utterances with infants with cochlear implants compared to hearing peers (Time 2), and mothers of infants with profound hearing loss used frequent directives and prohibitions both before and after cochlear implantation. Together, mothers and infants adapted relatively quickly to infants' access to cochlear implants, showing improved interactional synchrony, increased infant word use, and levels of maternal language complexity compatible with infants' word use, all within seven months of cochlear implant activation.

Age-related changes in prosodic features of maternal speech to prelingually deaf infants with cochlear implants.

This study investigated prosodic and structural characteristics of infant-directed speech to hearing-impaired infants as they gain hearing experience with a cochlear implant over a 12-month period of time. Mothers were recorded during a play interaction with their HI infants (N = 27, mean age 18.4 months) at 3, 6, and 12 months post-implantation. Two separate control groups of mothers with age-matched normal-hearing infants (NH-AM) (N = 21, mean age 18.1 months) and hearing experience-matched normal-hearing infants (NH-EM) (N = 24, mean age 3.1 months) were recorded at three testing sessions. Mothers produced less exaggerated pitch characteristics, a larger number of syllables per utterance, and faster speaking rate when interacting with NH-AM as compared to HI infants. Mothers also produced more syllables and demonstrated a trend suggesting faster speaking rate in speech to NH-EM relative to HI infants. Age-related modifications included decreased pitch standard deviation and increased number of syllables in speech to NH-AM infants and increased number of syllables in speech to HI and NH-EM infants across the 12-month period. These results suggest that mothers are sensitive to the hearing status of their infants and modify characteristics of infant-direct speech over time.

Speech intelligibility and prosody production in children with cochlear implants.

OBJECTIVES: The purpose of the current study was to examine the relation between speech intelligibility and prosody production in children who use cochlear implants. METHODS: The Beginner's Intelligibility Test (BIT) and Prosodic Utterance Production (PUP) task were administered to 15 children who use cochlear implants and 10 children with normal hearing. Adult listeners with normal hearing judged the intelligibility of the words in the BIT sentences, identified the PUP sentences as one of four grammatical or emotional moods (i.e., declarative, interrogative, happy, or sad), and rated the PUP sentences according to how well they thought the child conveyed the designated mood. RESULTS: Percent correct scores were higher for intelligibility than for prosody and higher for children with normal hearing than for children with cochlear implants. Declarative sentences were most readily identified and received the highest ratings by adult listeners; interrogative sentences were least readily identified and received the lowest ratings. Correlations between intelligibility and all mood identification and rating scores except declarative were not significant. DISCUSSION: The findings suggest that the development of speech intelligibility progresses ahead of prosody in both children with cochlear implants and children with normal hearing; however, children with normal hearing still perform better than children with cochlear implants on measures of intelligibility and prosody even after accounting for hearing age. Problems with interrogative intonation may be related to more general restrictions on rising intonation, and the correlation results indicate that intelligibility and sentence intonation may be relatively dissociated at these ages. LEARNING OUTCOMES: As a result of this activity, readers will be able to describe (1) methods for measuring speech intelligibility and prosody production in children with cochlear implants and children with normal hearing, (2) the differences between children with normal hearing and children with cochlear implants on measures of speech intelligibility and prosody production, and (3) the relations between speech intelligibility and prosody production in children with cochlear implants and children with normal hearing.

Effects of simultaneous speech and sign on infants' attention to spoken language.

OBJECTIVES: To examine the hypothesis that infants receiving a degraded auditory signal have more difficulty segmenting words from fluent speech if familiarized with the words presented in both speech and sign compared to familiarization with the words presented in speech only. STUDY DESIGN: Experiment utilizing an infant-controlled visual preference procedure. METHODS: Twenty 8.5-month-old normal-hearing infants completed testing. Infants were familiarized with repetitions of words in either the speech + sign (n = 10) or the speech only (n = 10) condition. Infants were then presented with four six-sentence passages using an infant-controlled visual preference procedure. Every sentence in two of the passages contained the words presented in the familiarization phase, whereas none of the sentences in the other two passages contained familiar words. RESULTS: Infants exposed to the speech + sign condition looked at familiar word passages for 15.3 seconds and at nonfamiliar word passages for 15.6 seconds, t (9) = -0.130, p = .45. Infants exposed to the speech only condition looked at familiar word passages for 20.9 seconds and to nonfamiliar word passages for 15.9 seconds. This difference was statistically significant, t (9) = 2.076, p = .03. CONCLUSIONS: Infants' ability to segment words from degraded speech is negatively affected when these words are initially presented in simultaneous speech and sign. The current study suggests that a decreased ability to segment words from fluent speech may contribute towards the poorer performance of pediatric cochlear implant recipients in total communication settings on a wide range of spoken language outcome measures.