On not knowing the music: Disruptions to synchrony of affect in the vocal channel between mothers and their children with callous-unemotional (CU) traits

Abstract

Examining mechanisms for the transmission of emotion between caregivers and their children is a growing concern for theories of child psychological development. One established mechanism for such transmission is biobehavioural synchrony, a phenomenon that is considered normative in early childhood and that has been associated with the child's capacity for empathy across development. Yet very little is known about synchrony on features of vocal affect between mothers and their children beyond infancy, or about characteristics of the child that might disrupt such processes. This thesis proposes callous-unemotional (CU) traits as one such characteristic, due to impairments in emotion processing and empathy that characterise this population. Study 1 used a novel integrative paradigm of clinical psychological assessment, speech signal feature extraction, and the dynamic time series approach of cointegration to test the hypothesis that synchrony of vocal affect is a prevalent phenomenon in the interactions of mothers and their children aged 4 to 8 years (M = 6.04; SD = 1.50). Studying a large number of acoustic-prosodic parameters in a large sample of dyads (N = 79 dyads; 66% male children), synchrony was found to be a widespread occurrence during mother-child emotion talk, and both mothers and their children demonstrated the capacity to influence each other's vocal qualities. However, its prevalence was also dyad dependent. As hypothesised, Study 2 found that callous-unemotional traits were associated with disruption on a range of acoustic-prosodic parameters, particularly pitch and energy, and these disruptions were moderated by maternal characteristics. In contrast, child empathy was associated with positive relationships to synchrony on vocal parameters. Oppositional defiant disorder (ODD), a condition characterised by emotional and behavioural dysregulation, was not a predictor of disruption to synchrony. Study 3 investigated vocal parameters associated with characteristics of the child and found that callous-unemotional children, but not their mothers, displayed substantial differences on two key parameters of vocal expression: a narrower pitch range and a greater proportion of speaking time, findings that are consistent with the restricted affect and impaired empathy in the CU construct. For children with a diagnosis of ODD, the interactional system of mothers and their children was characterised by high levels of mutual vocal arousal. Study 4 investigated vocal features associated with caregiving qualities of the mother. Lower pitch and intensity values by both the mother and child characterised observed-rated attuned conversations, with linguistic content and acoustic-prosodic parameters working together to optimise conveyance of this important caregiving quality. Attunement was particularly notable in increasing the comparatively poor speaking time of high empathy children. There was no association between the mother's warmth or attunement and child CU traits, and these qualities did not moderate the shallower pitch range of high CU children. However the mother's dismissiveness was found to be particularly deleterious to the compromised pitch range of these children. This research is the first to demonstrate synchrony as a dynamic, bidirectional phenomenon prevalent across a large number of acoustic-prosodic parameters between mothers and their children, and to demonstrate the application of cointegration as a methodology to the study of acoustic-prosodic expression. It is the first study to show disruption to synchronous vocal processes - as well as other differences in vocal expression - for children with CU traits. The findings have implications for establishing the vocal channel as a bidirectional source of emotion contagion between mothers and their children, and for biobehavioural synchrony as a promising field of study for children with CU traits.