When infants talk, infants listen: pre-babbling infants prefer listening to speech with infant vocal properties

Infant-directed speech does not always involve exaggerated vowel distinctions: Evidence from Danish

This study compared the acoustic properties of 26 (100% female, 100% monolingual) Danish caregivers' spontaneous speech addressed to their 11- to 24-month-old infants (infant-directed speech, IDS) and an adult experimenter (adult-directed speech, ADS). The data were collected between 2016 and 2018 in Aarhus, Denmark. Prosodic properties of Danish IDS conformed to cross-linguistic patterns, with a higher pitch, greater pitch variability, and slower articulation rate than ADS. However, an acoustic analysis of vocalic properties revealed that Danish IDS had a reduced or similar vowel space, higher within-vowel variability, raised formants, and lower degree of vowel discriminability compared to ADS. None of the measures, except articulation rate, showed age-related differences. These results push for future research to conduct theory-driven comparisons across languages with distinct phonological systems.

Adults’ Perception of Children’s Vowel Production

The study examined the link between Korean-speaking children’s vowel production and its perception by inexperienced adults and also observed whether ongoing vowel changes in mid-back vowels affect adults’ perceptions when the vowels are produced by children. This study analyzed vowels in monosyllabic words produced by 20 children, ranging from 2 to 6 years old, with a focus on gender distinction, and used them as perceptual stimuli for word perception by 20 inexperienced adult listeners. Acoustic analyses indicated that F0 was not a reliable cue for distinguishing gender, but the first two formants served as reliable cues for gender distinction. The results confirmed that the spacing of the two low formants is linguistically and para-linguistically important in identifying vowel types and gender. However, a pair of non-low back vowels caused difficulties in correct vowel identification. Proximal distance between the vowels could be interpreted to result in the highest mismatch between children’s production and adults’ perception of the two non-low back vowels in the Korean language. We attribute the source of the highest mismatch of the two non-low back vowels to the ongoing sound change observed in high and mid-back vowels in adult speech. The ongoing vowel change is also observed in the children’s vowel space, which may well be shaped after the caregivers whose non-low back vowels are close to each other.

The use of complex structures with a word class change in Inuktitut child-directed speech

Caregivers typically use a simplified mode of the language – child-directed speech (CDS) – when addressing young children. In this study, we investigate the use of complex morphological structures with a word class change within a single word in Inuktitut CDS. Inuktitut is a polysynthetic agglutinative language of the Inuit–Yupik–Unangan language family spoken in arctic Quebec, which allows more than 10 morphemes per word and in which the meaning of an entire sentence can be expressed in one word. Clearly, such a complex morphological system presents special challenges for young children, which raises the question of whether caregivers shape their CDS in ways that facilitate acquisition. Using the data from mothers addressing eight Inuktitut-speaking children aged 0;11 to 3;6, we investigated whether the frequency and complexity of polysynthetic structures in CDS are dependent on the stage of the children’s linguistic development. The results demonstrate that the number and morphological complexity of the structures with a word class change increased as the children developed linguistically. The variety of nominalizers and verbalizers – the key components of such structures – also increased through the stages and were used in variation sets, which help children acquire morphological items by providing examples of use of the same morpheme in morphologically contrasting environments. These results show the presence of morphological simplification in Inuktitut CDS and demonstrate that such simplification is fine-tuned, i.e., that mothers are sensitive to their children’s level of linguistic development.

Emotional Speech Processing in 3- to 12-Month-Old Infants: Influences of Emotion Categories and Acoustic Parameters

PURPOSE

The aim of this study was to investigate infants' listening preference for emotional prosodies in spoken words and identify their acoustic correlates.

METHOD

Forty-six 3- to-12-month-old infants (M _age = 7.6 months) completed a central fixation (or look-to-listen) paradigm in which four emotional prosodies (happy, sad, angry, and neutral) were presented. Infants' looking time to the string of words was recorded as a proxy of their listening attention. Five acoustic variables-mean fundamental frequency (F0), word duration, intensity variation, harmonics-to-noise ratio (HNR), and spectral centroid-were also analyzed to account for infants' attentiveness to each emotion.

RESULTS

Infants generally preferred affective over neutral prosody, with more listening attention to the happy and sad voices. Happy sounds with breathy voice quality (low HNR) and less brightness (low spectral centroid) maintained infants' attention more. Sad speech with shorter word duration (i.e., faster speech rate), less breathiness, and more brightness gained infants' attention more than happy speech did. Infants listened less to angry than to happy and sad prosodies, and none of the acoustic variables were associated with infants' listening interests in angry voices. Neutral words with a lower F0 attracted infants' attention more than those with a higher F0. Neither age nor sex effects were observed.

CONCLUSIONS

This study provides evidence for infants' sensitivity to the prosodic patterns for the basic emotion categories in spoken words and how the acoustic properties of emotional speech may guide their attention. The results point to the need to study the interplay between early socioaffective and language development.

Setting the Stage for Speech Production: Infants Prefer Listening to Speech Sounds With Infant Vocal Resonances

PURPOSE

Current models of speech development argue for an early link between speech production and perception in infants. Recent data show that young infants (at 4-6 months) preferentially attend to speech sounds (vowels) with infant vocal properties compared to those with adult vocal properties, suggesting the presence of special "memory banks" for one's own nascent speech-like productions. This study investigated whether the vocal resonances (formants) of the infant vocal tract are sufficient to elicit this preference and whether this perceptual bias changes with age and emerging vocal production skills.

METHOD

We selectively manipulated the fundamental frequency (f₀ ) of vowels synthesized with formants specifying either an infant or adult vocal tract, and then tested the effects of those manipulations on the listening preferences of infants who were slightly older than those previously tested (at 6-8 months).

RESULTS

Unlike findings with younger infants (at 4-6 months), slightly older infants in Experiment 1 displayed a robust preference for vowels with infant formants over adult formants when f₀ was matched. The strength of this preference was also positively correlated with age among infants between 4 and 8 months. In Experiment 2, this preference favoring infant over adult formants was maintained when f₀ values were modulated.

CONCLUSIONS

Infants between 6 and 8 months of age displayed a robust and distinct preference for speech with resonances specifying a vocal tract that is similar in size and length to their own. This finding, together with data indicating that this preference is not present in younger infants and appears to increase with age, suggests that nascent knowledge of the motor schema of the vocal tract may play a role in shaping this perceptual bias, lending support to current models of speech development.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.17131805.

Does the Combination of Glottal and Supraglottic Acoustic Measures Improve Discrimination Between Women With and Without Voice Disorders?

AIM

To analyze the accuracy of traditional acoustic measurements (F0, perturbation, and noise) and formant measurements in discriminating between women with and without voice disorders, and with different laryngeal disorders.

STUDY DESIGN

A descriptive, cross-sectional, and retrospective.

METHOD

Two hundred and sixty women participated. All participants recorded the spoken vowel /Ɛ/ and underwent laryngeal visual examination. Acoustic measures of the mean and standard deviation of the fundamental frequency (F0), jitter, shimmer, glottal-to-noise excitation ratio, and the values of the first three formants (F1, F2, and F3) were obtained.

RESULTS

Individual acoustic measurements did not demonstrate adequate (<70%) performance when discriminating between women with and without voice disorders. The combination of the standard deviation of the F0, shimmer, glottal-to-noise excitation ratio, F1, F2, and F3 showed acceptable (>70%) performance in classifying women with and without voice disorders. Individual measures of jitter as well as F1 and F3 demonstrated acceptable (>70%) performance when distinguishing women with different laryngeal diagnoses, including without voice disorders (healthy larynges), Reinke's edema, unilateral vocal fold paralysis, and sulcus vocalis. The combination of acoustic measurements showed excellent (>80%) performance when discriminating women without voice disorder from those with Reinke's edema (mean of F0, F1, and F3) and with sulcus vocalis (mean of F0, F1, and F2).

CONCLUSIONS

Individual formant and traditional acoustic measurements do not demonstrate adequate performance when discriminating between women with and without voice disorders. However, the combination of traditional and formant measurements improves the discrimination between the presence and absence of voice disorders and differentiates several laryngeal diagnoses.

What Acoustic Studies Tell Us About Vowels in Developing and Disordered Speech

Purpose Literature was reviewed on the development of vowels in children's speech and on vowel disorders in children and adults, with an emphasis on studies using acoustic methods. Method Searches were conducted with PubMed/MEDLINE, Google Scholar, CINAHL, HighWire Press, and legacy sources in retrieved articles. The primary search items included, but were not limited to, vowels, vowel development, vowel disorders, vowel formants, vowel therapy, vowel inherent spectral change, speech rhythm, and prosody. Results/Discussion The main conclusions reached in this review are that vowels are (a) important to speech intelligibility; (b) intrinsically dynamic; (c) refined in both perceptual and productive aspects beyond the age typically given for their phonetic mastery; (d) produced to compensate for articulatory and auditory perturbations; (e) influenced by language and dialect even in early childhood; (f) affected by a variety of speech, language, and hearing disorders in children and adults; (g) inadequately assessed by standardized articulation tests; and (h) characterized by at least three factors-articulatory configuration, extrinsic and intrinsic regulation of duration, and role in speech rhythm and prosody. Also discussed are stages in typical vowel ontogeny, acoustic characterization of rhotic vowels, a sensory-motor perspective on vowel production, and implications for clinical assessment of vowels.

Effects of motion and audio-visual redundancy on upright and inverted face and feature preferences in 4-13-month old pre- and full-term NICU graduates

NICU infants are reported to have diminished social orientation and increased risk of socio-communicative disorders. In this eye tracking study, we used a preference for upright compared to inverted faces as a gauge of social interest in high medical risk full- and pre-term NICU infants. We examined the effects of facial motion and audio-visual redundancy on face and eye/mouth preferences across the first year. Upright and inverted baby faces were simultaneously presented in a paired-preference paradigm with motion and synchronized vocalization varied. NICU risk factors including birth weight, sex, and degree of CNS injury were examined. Overall, infants preferred the more socially salient upright faces, making this the first report, to our knowledge, of an upright compared to inverted face preference among high medical risk NICU infants. Infants with abnormalities on cranial ultrasound displayed lower social interest, i.e. less of a preferential interest in upright faces, when viewing static faces. However, motion selectively increased their upright face looking time to a level equal that of infants in other CNS injury groups. We also observed an age-related sex effect suggesting higher risk in NICU males. Females increased their attention to the mouth in upright faces across the first year, especially between 7-10 months, but males did not. Although vocalization increased diffuse attention toward the screen, contrary to our predictions, there was no evidence that the audio-visual redundancy embodied in a vocalizing face focused additional attention on upright faces or mouths. This unexpected result may suggest a vulnerability in response to talking faces among NICU infants that could potentially affect later verbal and socio-communicative development.

Developmental Effects in Children's Ability to Benefit From F0 Differences Between Target and Masker Speech

OBJECTIVES

The objectives of this study were to (1) evaluate the extent to which school-age children benefit from fundamental frequency (F0) differences between target words and competing two-talker speech, and (2) assess whether this benefit changes with age. It was predicted that while children would be more susceptible to speech-in-speech masking compared to adults, they would benefit from differences in F0 between target and masker speech. A second experiment was conducted to evaluate the relationship between frequency discrimination thresholds and the ability to benefit from target/masker differences in F0.

DESIGN

Listeners were children (5 to 15 years) and adults (20 to 36 years) with normal hearing. In the first experiment, speech reception thresholds (SRTs) for disyllabic words were measured in a continuous, 60-dB SPL two-talker speech masker. The same male talker produced both the target and masker speech (average F0 = 120 Hz). The level of the target words was adaptively varied to estimate the level associated with 71% correct identification. The procedure was a four-alternative forced-choice with a picture-pointing response. Target words either had the same mean F0 as the masker or it was shifted up by 3, 6, or 9 semitones. To determine the benefit of target/masker F0 separation on word recognition, masking release was computed by subtracting thresholds in each shifted-F0 condition from the threshold in the unshifted-F0 condition. In the second experiment, frequency discrimination thresholds were collected for a subset of listeners to determine whether sensitivity to F0 differences would be predictive of SRTs. The standard was the syllable /ba/ with an F0 of 250 Hz; the target stimuli had a higher F0. Discrimination thresholds were measured using a three-alternative, three-interval forced choice procedure.

RESULTS

Younger children (5 to 12 years) had significantly poorer SRTs than older children (13 to 15 years) and adults in the unshifted-F0 condition. The benefit of F0 separations generally increased with increasing child age and magnitude of target/masker F0 separation. For 5- to 7-year-olds, there was a small benefit of F0 separation in the 9-semitone condition only. For 8- to 12-year-olds, there was a benefit from both 6- and 9-semitone separations, but to a lesser degree than what was observed for older children (13 to 15 years) and adults, who showed a substantial benefit in the 6- and 9-semitone conditions. Examination of individual data found that children younger than 7 years of age did not benefit from any of the F0 separations tested. Results for the frequency discrimination task indicated that, while there was a trend for improved thresholds with increasing age, these thresholds were not predictive of the ability to use F0 differences in the speech-in-speech recognition task after controlling for age.

CONCLUSIONS

The overall pattern of results suggests that children's ability to benefit from F0 differences in speech-in-speech recognition follows a prolonged developmental trajectory. Younger children are less able to capitalize on differences in F0 between target and masker speech. The extent to which individual children benefitted from target/masker F0 differences was not associated with their frequency discrimination thresholds.

Developmental sociolinguistics: Children's acquisition of language variation

Developmental sociolinguistics is a rapidly evolving interdisciplinary framework that builds upon theoretical and methodological contributions from multiple disciplines (i.e., sociolinguistics, language acquisition, the speech sciences, developmental psychology, and psycholinguistics). A core assumption of this framework is that language is by its very nature variable, and that much of this variability is informative, as it is (probabilistically) governed by a variety of factors-including linguistic context, social or cultural context, the relationship between speaker and addressee, a language user's geographic origin, and a language user's gender identity. It is becoming increasingly clear that consideration of these factors is absolutely essential to developing realistic and ecologically valid models of language development. Given the central importance of language in our social world, a more complete understanding of early social development will also require a deeper understanding of when and how language variation influences children's social inferences and behavior. As the cross-pollination between formerly disparate fields continues, we anticipate a paradigm shift in the way many language researchers conceptualize the challenge of early acquisition. This article is categorized under: Linguistics > Linguistic Theory Linguistics > Language Acquisition Neuroscience > Development Psychology > Language.

Developmental Effects in Masking Release for Speech-in-Speech Perception Due to a Target/Masker Sex Mismatch

OBJECTIVES

The purpose of this study was to evaluate the extent to which infants, school-age children, and adults benefit from a target/masker sex mismatch in the context of speech detection or recognition in a background of 2 competing talkers. It was hypothesized that the ability to benefit from a target/masker sex mismatch develops between infancy and the early school-age years, as children gain listening experience in multi-talker environments.

DESIGN

Listeners were infants (7 to 13 months), children (5 to 10 years), and adults (18 to 33 years) with normal hearing. A series of five experiments compared speech detection or recognition in continuous two-talker speech across target/masker conditions that were sex matched or sex mismatched. In experiments 1 and 2, an observer-based, single-interval procedure was used to estimate speech detection thresholds for a spondaic word in a two-talker speech masker. In experiments 3 and 4, speech recognition thresholds were estimated in continuous two-talker speech using a four-alternative, forced-choice procedure. In experiment 5, speech reception thresholds (SRTs) were estimated for adults using the forced-choice recognition procedure after ideal time-frequency segregation processing was applied to the stimuli.

RESULTS

Speech detection thresholds for adults tested in experiments 1 and 2 were significantly higher when the target word and speech masker were matched in sex than when they were mismatched, but thresholds for infants were similar across sex-matched and sex-mismatched conditions. Results for experiments 3 and 4 showed that school-age children and adults benefit from a target/masker sex mismatch for a forced-choice word recognition task. Children, however, obtained greater benefit than adults in 1 condition, perhaps due to greater susceptibility to masking overall. In experiment 5, adults had substantial threshold reductions and more uniform performance across the 4 conditions evaluated in experiments 3 and 4 after the application of ideal time-frequency segregation to the stimuli.

CONCLUSIONS

The pattern of results observed across experiments suggests that the ability to take advantage of differences in vocal characteristics typically found between speech produced by male and female talkers develops between infancy and the school-age years. Considerable child-adult differences in susceptibility to speech-in-speech masking were observed for school-age children as old as 11 years of age in both sex-matched and sex-mismatched conditions.

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.

The nature and emotional valence of a prime influences the processing of emotional faces in adults and children

A large body of research has investigated both the emotional elaboration of facial stimuli in adults and the development of children’s recognition of emotional expressions. Yet, it is still not clear whether children’s ability to recognize an emotional face may be modulated by prior exposure to a different face, and whether an emotional expression may exert an effect on the processing of subsequently encountered facial emotional expressions. We tested in three experiments the recognition of happy and angry target faces preceded by neutral faces or objects (Experiment 1) and happy or angry faces (Experiment 2A and Experiment 2B) using an affective priming task in adults and 7- and 5-year-old children. Results showed a standard prime effect for neutral faces (Experiment 1) for all participants, and for happy faces in children (Experiment 2A) and adults (Experiment 2B). Otherwise, angry faces elicited negative priming effects in all participants (Experiment 2A). Overall, our findings showed that both prior exposure to a face per se and the emotional valence of the prime face have an impact on subsequent processing of facial emotional information. Implications for emotional processing are discussed.

Toddlers' comprehension of adult and child talkers: Adult targets versus vocal tract similarity

How do children represent words? If lexical representations are based on encoding the indexical characteristics of frequently-heard speakers, this predicts that speakers like a child's own mother should be best understood. Alternatively, if they are based on the child's own motor productions, this predicts an own-voice advantage in word recognition. Here, we address this question by presenting 2.5-year-olds with recordings of their own voice, another child's voice, their own mother's voice, and another mother's voice in a child-friendly eye-tracking procedure. No own-voice or own-mother advantage was observed. Rather, children uniformly performed better on adult voices than child voices, even performing better for unfamiliar adult voices than own voices. We conclude that children represent words not in the form of own-voice motor codes or frequently heard speakers, but on the basis of adult speech targets.

The origins of babytalk: smiling, teaching or social convergence?

When addressing their young infants, parents systematically modify their speech. Such infant-directed speech (IDS) contains exaggerated vowel formants, which have been proposed to foster language development via articulation of more distinct speech sounds. Here, this assumption is rigorously tested using both acoustic and, for the first time, fine-grained articulatory measures. Mothers were recorded speaking to their infant and to another adult, and measures were taken of their acoustic vowel space, their tongue and lip movements and the length of their vocal tract. Results showed that infant- but not adult-directed speech contains acoustically exaggerated vowels, and these are not the product of adjustments to tongue or to lip movements. Rather, they are the product of a shortened vocal tract due to a raised larynx, which can be ascribed to speakers' unconscious effort to appear smaller and more non-threatening to the young infant. This adjustment in IDS may be a vestige of early mother-infant interactions, which had as its primary purpose the transmission of non-aggressiveness and/or a primitive manifestation of pre-linguistic vocal social convergence of the mother to her infant. With the advent of human language, this vestige then acquired a secondary purpose-facilitating language acquisition via the serendipitously exaggerated vowels.