Listeners' perception of lexical stress in the first words of infants with cochlear implants and normally hearing infants.

Normally hearing (NH) infants are able to produce lexical stress in their first words, but congenitally hearing-impaired children with cochlear implants (CI) may find this more challenging, given the limited transmission of spectro-temporal information by the implant. Acoustic research has shown that the acoustic cues to stress in the first words of Dutch-acquiring CI infants are less pronounced (Pettinato, De Clerck, Verhoeven, & Gillis, 2017). The present study investigates how listeners perceive lexical stress in the first words of CI and NH infants. Two research questions are addressed: (1) How successful are CI and NH children in implementing the prosodic cues to prominence? (2) Is the degree of stress in CI and NH words perceived to be similar? The stimuli used in this study are disyllabic words (n = 1089) produced by 9 infants with CI and 9 NH infants acquiring Dutch. The words were presented to adult listeners in a listening experiment, in which they assessed the stress pattern on a continuous visual analogue scale (VAS) which expresses to what extent syllables are perceived as stressed. The results show that listeners perceive typical word stress production in the first words of infants with CI. The words of CI and NH infants were rated in agreement with the target stress pattern as often, and trochaic words were rated more frequently as such than iambic words. Listeners more frequently perceive unstressed syllables in the first words of infants with CI. However, for the words that are perceived to be clearly stressed, the degree of word stress is comparable in the two groups, and both infant groups are perceived to produce more contrast between stressed and unstressed syllables in trochees than in iambs. It is concluded that that acoustic differences between CI and NH infants' stress production are not necessarily perceptually salient.

Simulating speech processing with cochlear implants: How does channel interaction affect learning in neural networks?

We introduce a novel machine learning approach for investigating speech processing with cochlear implants (CIs)-prostheses used to replace a damaged inner ear. Concretely, we use a simple perceptron and a deep convolutional network to classify speech spectrograms that are modified to approximate CI-delivered speech. Implant-delivered signals suffer from reduced spectral resolution, chiefly due to a small number of frequency channels and a phenomenon called channel interaction. The latter involves the spread of information from neighboring channels to similar populations of neurons and can be modeled by linearly combining adjacent channels. We find that early during training, this input modification degrades performance if the networks are first pre-trained on high-resolution speech-with a larger number of channels, and without added channel interaction. This suggests that the spectral degradation caused by channel interaction alters the signal to conflict with perceptual expectations acquired from high-resolution speech. We thus predict that a reduction of channel interaction will accelerate learning in CI users who are implanted after having adapted to high-resolution speech during normal hearing. (The code for replicating our experiments is available online: https://github.com/clips/SimulatingCochlearImplants).

Expansion of Prosodic Abilities at the Transition From Babble to Words: A Comparison Between Children With Cochlear Implants and Normally Hearing Children.

OBJECTIVES: This longitudinal study examined the effect of emerging vocabulary production on the ability to produce the phonetic cues to prosodic prominence in babbled and lexical disyllables of infants with cochlear implants (CI) and normally hearing (NH) infants. Current research on typical language acquisition emphasizes the importance of vocabulary development for phonological and phonetic acquisition. Children with CI experience significant difficulties with the perception and production of prosody, and the role of possible top-down effects is, therefore, particularly relevant for this population. DESIGN: Isolated disyllabic babble and first words were identified and segmented in longitudinal audio-video recordings and transcriptions for nine NH infants and nine infants with CI interacting with their parents. Monthly recordings were included from the onset of babbling until children had reached a cumulative vocabulary of 200 words. Three cues to prosodic prominence, fundamental frequency (f0), intensity, and duration, were measured in the vocalic portions of stand-alone disyllables. To represent the degree of prosodic differentiation between two syllables in an utterance, the raw values for intensity and duration were transformed to ratios, and for f0, a measure of the perceptual distance in semitones was derived. The degree of prosodic differentiation for disyllabic babble and words for each cue was compared between groups. In addition, group and individual tendencies on the types of stress patterns for babble and words were also examined. RESULTS: The CI group had overall smaller pitch and intensity distances than the NH group. For the NH group, words had greater pitch and intensity distances than babbled disyllables. Especially for pitch distance, this was accompanied by a shift toward a more clearly expressed stress pattern that reflected the influence of the ambient language. For the CI group, the same expansion in words did not take place for pitch. For intensity, the CI group gave evidence of some increase of prosodic differentiation. The results for the duration measure showed evidence of utterance final lengthening in both groups. In words, the CI group significantly reduced durational differences between syllables so that a more even-timed, less differentiated pattern emerged. CONCLUSIONS: The onset of vocabulary production did not have the same facilitatory effect for the CI infants on the production of phonetic cues for prosody, especially for pitch. It was argued that the results for duration may reflect greater articulatory difficulties in words for the CI group than the NH group. It was suggested that the lack of clear top-down effects of the vocabulary in the CI group may be because of a lag in development caused by an initial lack of auditory stimulation, possibly compounded by the absence of auditory feedback during the babble phase.

Is prosodic production driven by lexical development? Longitudinal evidence from babble and words.

This study investigated the relation between lexical development and the production of prosodic prominence in disyllabic babble and words. Monthly recordings from nine typically developing Belgian-Dutch-speaking infants were analyzed from the onset of babbling until a cumulative vocabulary of 200 words was reached. The differentiation between the two syllables of isolated disyllabic utterances was computed for f0, intensity, and duration measurements. Results showed that the ambient trochaic pattern emerged in babble, but became enhanced in words. Words showed more prosodic differentiation in terms of f0 and intensity and a more even duration ratio. Age or vocabulary size did not predict the expansion of f0 or intensity in words, whereas vocabulary size was related to the production of more even-timed syllables. The findings are discussed in terms of lexicalist accounts of phonetic development and a potential phonetic highlighting function of first words.

Suprasegmental Characteristics of Spontaneous Speech Produced in Good and Challenging Communicative Conditions by Talkers Aged 9-14 Years.

Purpose: This study investigated the acoustic characteristics of spontaneous speech by talkers aged 9-14 years and their ability to adapt these characteristics to maintain effective communication when intelligibility was artificially degraded for their interlocutor. Method: Recordings were made for 96 children (50 female participants, 46 male participants) engaged in a problem-solving task with a same-sex friend; recordings for 20 adults were used as reference. The task was carried out in good listening conditions (normal transmission) and in degraded transmission conditions. Articulation rate, median fundamental frequency (f0), f0 range, and relative energy in the 1- to 3-kHz range were analyzed. Results: With increasing age, children significantly reduced their median f0 and f0 range, became faster talkers, and reduced their mid-frequency energy in spontaneous speech. Children produced similar clear speech adaptations (in degraded transmission conditions) as adults, but only children aged 11-14 years increased their f0 range, an unhelpful strategy not transmitted via the vocoder. Changes made by children were consistent with a general increase in vocal effort. Conclusion: Further developments in speech production take place during later childhood. Children use clear speech strategies to benefit an interlocutor facing intelligibility problems but may not be able to attune these strategies to the same degree as adults.

Cross-accent intelligibility of speech in noise: long-term familiarity and short-term familiarization.

Listeners must cope with a great deal of variability in the speech signal, and thus theories of speech perception must also account for variability, which comes from a number of sources, including variation between accents. It is well known that there is a processing cost when listening to speech in an accent other than one's own, but recent work has suggested that this cost is reduced when listening to a familiar accent widely represented in the media, and/or when short amounts of exposure to an accent are provided. Little is known, however, about how these factors (long-term familiarity and short-term familiarization with an accent) interact. The current study tested this interaction by playing listeners difficult-to-segment sentences in noise, before and after a familiarization period where the same sentences were heard in the clear, allowing us to manipulate short-term familiarization. Listeners were speakers of either Glasgow English or Standard Southern British English, and they listened to speech in either their own or the other accent, thereby allowing us to manipulate long-term familiarity. Results suggest that both long-term familiarity and short-term familiarization mitigate the perceptual processing costs of listening to an accent that is not one's own, but seem not to compensate for them entirely, even when the accent is widely heard in the media.

Spontaneous belief attribution in younger siblings of children on the autism spectrum.

The recent development in the measurements of spontaneous mental state understanding, employing eye-movements instead of verbal responses, has opened new opportunities for understanding the developmental origin of "mind-reading" impairments frequently described in autism spectrum disorders (ASDs). Our main aim was to characterize the relationship between mental state understanding and the broader autism phenotype, early in childhood. An eye-tracker was used to capture anticipatory looking as a measure of false beliefs attribution in 3-year-old children with a family history of autism (at-risk participants, n = 47) and controls (control participants, n = 39). Unlike controls, the at-risk group, independent of their clinical outcome (ASD, broader autism phenotype or typically developing), performed at chance. Performance was not related to children's verbal or general IQ, nor was it explained by children "missing out" on crucial information, as shown by an analysis of visual scanning during the task. We conclude that difficulties with using mental state understanding for action prediction may be an endophenotype of autism spectrum disorders.

Developmental and gender-related trends of intra-talker variability in consonant production.

This study investigates the effect of age and gender on the internal structure, cross-category distance, and discriminability of phonemic categories for two contrasts varying in fricative place of articulation (/s/-/∫/) and stop voicing (/b/-/p/) in word-initial tokens spoken by adults and normally developing children aged 9-14 yr. Vast between- and within-talker variability was observed with 16% of speakers exhibiting some degree of overlap between phonemic categories-a possible contribution to the range of talker intelligibility found in the literature. Females of all ages produced farther and thus more discriminable categories than males, although gender-marking for fricative between-category distance did not emerge until approximately 11 yr of age. Children produced farther yet also much more dispersed categories than adults with increasing discriminability with age, such that by age 13, children's categories were no less discriminable than those of adults. However, children's ages did not predict category distance or dispersion, indicating that convergence on adult-like category structure must occur later in adolescence.

Accent attribution in speakers with Foreign Accent Syndrome.

PURPOSE: The main aim of this experiment was to investigate the perception of Foreign Accent Syndrome in comparison to speakers with an authentic foreign accent. METHOD: Three groups of listeners attributed accents to conversational speech samples of 5 FAS speakers which were embedded amongst those of 5 speakers with a real foreign accent and 5 native speaker controls. The listening panels differed in their familiarity with foreign accented speech and speech pathology. RESULTS: The findings indicate that listeners' perceptual responses to the three groups of speakers were essentially different at all levels of analysis. The native speaker controls were unequivocally recognized as native speakers of Dutch while the speakers with a real foreign accent were very reliably assessed as non-native speakers. The speakers with Foreign Accent Syndrome, however, were in some sense perceived as foreign and in some sense as native by listeners, but not as foreign as speakers with a real foreign accent nor as native as real native speakers. These results are accounted for in terms of a misinterpretation of markers of speech pathology as markers regional affiliation. CONCLUSIONS: The findings of the experiment are consistent with the idea that the very nature of the foreign accent is different in both groups of speakers, although it cannot be fully excluded that the foreign impression in the two groups is one of degree. LEARNING OUTCOMES: Readers are able to: (1) define Foreign Accent Syndrome as a motor speech disorder and identify the different subtypes of FAS, (2) describe the most important differences in listeners' perceptual reactions to FAS and real foreign accents, and (3) discuss the findings of the present study in relation to other studies investigating accent attribution in FAS.