Vocal communication across cultures: theoretical and methodological issues

Socioeconomic Inequalities Affect Brain Responses of Infants Growing Up in Germany

Developmental changes in functional neural networks are sensitive to environmental influences. This EEG study investigated how infant brain responses relate to the social context that their families live in. Event-related potentials of 255 healthy, awake infants between six and fourteen months were measured during a passive auditory oddball paradigm. Infants were presented with 200 standard tones and 48 randomly distributed deviants. All infants are part of a longitudinal study focusing on families with socioeconomic and/or cultural challenges (Bremen Initiative to Foster Early Childhood Development; BRISE; Germany). As part of their familial socioeconomic status (SES), parental level of education and infant's migration background were assessed with questionnaires. For 30.6% of the infants both parents had a low level of education (≤10 years of schooling) and for 43.1% of the infants at least one parent was born abroad. The N2-P3a complex is associated with unintentional directing of attention to deviant stimuli and was analysed in frontocentral brain regions. Age was utilised as a control variable. Our results show that tone deviations in infants trigger an immature N2-P3a complex. Contrary to studies with older children or adults, the N2 amplitude was more positive for deviants than for standards. This may be related to an immature superposition of the N2 with the P3a. For infants whose parents had no high-school degree and were born abroad, this tendency was increased, indicating that facing multiple challenges as a young family impacts on the infant's early neural development. As such, attending to unexpected stimulus changes may be important for early learning processes. Variations of the infant N2-P3a complex may, thus, relate to early changes in attentional capacity and learning experiences due to familial challenges. This points towards the importance of early prevention programs.

Vocal Characteristics of Infants at Risk for Speech Motor Involvement: A Scoping Review

PURPOSE

The purpose of this scoping review was to (a) summarize methodological characteristics of studies examining vocal characteristics of infants at high risk for neurological speech motor involvement and (b) report the state of the high-quality evidence on vocal characteristic trends of infants diagnosed or at high risk for cerebral palsy (CP).

METHOD

The PRISMA (Preferred Reporting Items of Systematic Reviews and Meta-Analyses) extension for scoping reviews was followed for reporting our review. Studies measured prelinguistic vocal characteristics of infants under 24 months with birth risk or genetic conditions known to commonly present with speech motor involvement. Fifty-five studies met criteria for Part 1. Eleven studies met criteria for synthesis in Part 2.

RESULTS

A smaller percentage of studies examined infants with or at risk for CP compared to studies examining genetic conditions such as Down syndrome. The median year of publication was 1999, with a median sample size of nine participants. Most studies were conducted in laboratory settings and used human coding of vocalizations produced during caregiver-child interactions. Substantial methodological differences were noted across all studies. A small number of high-quality studies of infants with or at risk for CP revealed high rates of marginal babbling, low rates of canonical babbling, and limited consonant diversity under 24 months. Mixed findings were noted across studies of general birth risk factors.

CONCLUSIONS

There is limited evidence available to support the early detection of speech motor involvement. Large methodological differences currently impact the ability to synthesize findings across studies. There is a critical need to conduct longitudinal research with larger sample sizes and advanced, modern technologies to detect vocal precursors of speech impairment to support the accurate diagnosis and prognosis of speech development in infants with CP and other clinical populations.

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.

Evaluating the Relative Perceptual Salience of Linguistic and Emotional Prosody in Quiet and Noisy Contexts

How people recognize linguistic and emotional prosody in different listening conditions is essential for understanding the complex interplay between social context, cognition, and communication. The perception of both lexical tones and emotional prosody depends on prosodic features including pitch, intensity, duration, and voice quality. However, it is unclear which aspect of prosody is perceptually more salient and resistant to noise. This study aimed to investigate the relative perceptual salience of emotional prosody and lexical tone recognition in quiet and in the presence of multi-talker babble noise. Forty young adults randomly sampled from a pool of native Mandarin Chinese with normal hearing listened to monosyllables either with or without background babble noise and completed two identification tasks, one for emotion recognition and the other for lexical tone recognition. Accuracy and speed were recorded and analyzed using generalized linear mixed-effects models. Compared with emotional prosody, lexical tones were more perceptually salient in multi-talker babble noise. Native Mandarin Chinese participants identified lexical tones more accurately and quickly than vocal emotions at the same signal-to-noise ratio. Acoustic and cognitive dissimilarities between linguistic prosody and emotional prosody may have led to the phenomenon, which calls for further explorations into the underlying psychobiological and neurophysiological mechanisms.

A systematic review and Bayesian meta-analysis of the acoustic features of infant-directed speech

When speaking to infants, adults often produce speech that differs systematically from that directed to other adults. To quantify the acoustic properties of this speech style across a wide variety of languages and cultures, we extracted results from empirical studies on the acoustic features of infant-directed speech. We analysed data from 88 unique studies (734 effect sizes) on the following five acoustic parameters that have been systematically examined in the literature: fundamental frequency (f₀), f₀ variability, vowel space area, articulation rate and vowel duration. Moderator analyses were conducted in hierarchical Bayesian robust regression models to examine how these features change with infant age and differ across languages, experimental tasks and recording environments. The moderator analyses indicated that f₀, articulation rate and vowel duration became more similar to adult-directed speech over time, whereas f₀ variability and vowel space area exhibited stability throughout development. These results point the way for future research to disentangle different accounts of the functions and learnability of infant-directed speech by conducting theory-driven comparisons among different languages and using computational models to formulate testable predictions.

The Role of Contextual Information in Classifying Spontaneous Social Laughter

Laughter is a ubiquitous and important social signal, but its nature is yet to be fully explored. One of the open empirical questions is about the role of context in the interpretation of laughter. Can laughs presented on their own convey specific feelings and social motives? How influential is social context when a person tries to understand the meaning of a laugh? Here we test the extent to which the classification of laughs produced in different situations is guided by knowing the context within which these laughs were produced. In the current study, stimuli were spontaneous laughs recorded in social situations engineered to elicit amusement, embarrassment, and schadenfreude. In a between-subjects design, participants classified these laughs being assigned to one of the four experimental conditions: audio only, audio-visual, side-by-side videos of two interactants, and side-by-side videos accompanied by a brief vignette. Participants’ task was to label each laugh as an instance of amusement, embarrassment, or schadenfreude laugh, or “other.” Laughs produced in situations inducing embarrassment were classified more accurately than laughs produced in other situations. Most importantly, eliminating information about the social settings in which laughs were produced decreased participants’ classification accuracy such that accuracy was no better than chance in the experimental conditions providing minimal contextual information. Our findings demonstrate the importance of context in the interpretation of laughter and highlight the complexity of experimental investigations of schadenfreude displays.