Vocal communication is tied to interpersonal arousal coupling in caregiver-infant dyads

Abstract

It has been argued that a necessary condition for the emergence of speech in humans is the ability to vocalize irrespectively of underlying affective states, but when and how this happens during development remains unclear. To examine this, we used wearable microphones and autonomic sensors to collect multimodal naturalistic datasets from 12-month-olds and their caregivers. We observed that, across the day, clusters of vocalisations occur during elevated infant and caregiver arousal. This relationship is stronger in infants than caregivers: caregivers vocalizations show greater decoupling with their own states of arousal, and their vocal production is more influenced by the infant's arousal than their own. Different types of vocalisation elicit different patterns of change across the dyad. Cries occur following reduced infant arousal stability and lead to increased child-caregiver arousal coupling, and decreased infant arousal. Speech-like vocalisations also occur at elevated arousal, but lead to longer-lasting increases in arousal, and elicit more parental verbal responses. Our results suggest that: 12-month-old infants' vocalisations are strongly contingent on their arousal state (for both cries and speech-like vocalisations), whereas adults' vocalisations are more flexibly tied to their own arousal; that cries and speech-like vocalisations alter the intra-dyadic dynamics of arousal in different ways, which may be an important factor driving speech development; and that this selection mechanism which drives vocal development is anchored in our stress physiology.

Parent–infant affect synchrony during social and solo play

“…As similar physiological increases occur in infants who are crying, these changes may drive short-term increases in parent-child arousal synchrony, which are observed following negative affect vocalizations (such as cries) but not following positive affect vocalizations [36,37]. Positive affect vocalizations are, though, more likely to elicit carer speech in response, during both infancy [36] and toddlerhood [38,39]. Facial displays of positive affect (such as smiles) also reliably elicit behavioural responses [40].…”

“…For example, in real-world home settings infant negative affect vocalizations (such as cries) elicit larger changes in parents' physiological arousal than positive affect vocalizations do [34][35][36]. As similar physiological increases occur in infants who are crying, these changes may drive short-term increases in parent-child arousal synchrony, which are observed following negative affect vocalizations (such as cries) but not following positive affect vocalizations [36,37]. Positive affect vocalizations are, though, more likely to elicit carer speech in response, during both infancy [36] and toddlerhood [38,39].…”

“…Positive affect vocalizations are, though, more likely to elicit carer speech in response, during both infancy [36] and toddlerhood [38,39]. Facial displays of positive affect (such as smiles) also reliably elicit behavioural responses [40].…”

Annual Research Review. ‘There, the dance is - at the still point of the turning world’: dynamic systems perspectives on co-regulation and dysregulation during early development

“…colic). For example, infant cries elicit caregiver responses, including increased caregiver arousal stability and increased caregiver-child arousal coupling, in the time following the vocalisation, which are followed by decreases in child arousal (Wass et al, 2019(Wass et al, , 2022.…”

“…S. Zhang & Ghazanfar, 2020) and human (Wass et al, 2022) research suggests that early vocal behaviours co-occur with autonomic nervous system fluctuations. For example, in 10-monthold infants both cries and speech-like vocalisations are relatively inflexible with regard to arousal during early development, insofar as both are more likely to occur around elevated infant arousal; but whereas cries lead to decreases in arousal, speech-like vocalisations lead to sustained increases in infant arousal, and to an increased rate of speech-like vocalisations in response (Wass et al, 2022). Caregiver speech, in contrast, appears not to be attuned to the caregiver's own arousal (in contrast to primate work (Y. S. , but is attuned to their child's arousal (Wass et al, 2022).…”