Nadège Bourvis

Dynamics of Non-Verbal Vocalizations and Hormones during Father-Infant Interaction

Although researchers have established the roles of oxytocin (OT) in promoting affiliative bonds and cortisol (CT) in adapting to stress, the investigation of their interplay with non-verbal behaviors has only recently begun. In this study, we employed social signal-processing techniques to investigate relationships between non-verbal features: infant and father vocalizations, infant-directed speech, speech turn-taking (STT) and hormonal dynamics (OT and CT). Thirty-five fathers were asked to interact with their infants following the fathers self-administration of OT or placebo. We consider the three episodes of the Still Face (SF) paradigm: (1) a baseline normal interaction episode, (2) the SF episode, in which the father becomes unresponsive and maintains a neutral facial expression, and (3) a reunion in which parents and their infants re-engage in interaction. This paradigm elicited stress in the infant. Statistical relationships are assessed by correlation analysis and linear mixed models (LMMs). The results indicate that (i) infant vocalization and STT are key social cues regulating interactions during the stress-inducing and reunion episodes, with infant vocalization leading the interaction dynamics; (ii) father empty pause was the main adaptive behavior of fathers after SF; (iii) OT did not modulate infant STT or father STT/fatherese; (iv) CT appeared to modulate the interaction.

Pre-linguistic infants employ complex communicative loops to engage mothers in social exchanges and repair interaction ruptures

Language has long been identified as a powerful communicative tool among humans. Yet, pre-linguistic communication, which is common in many species, is also used by human infants prior to the acquisition of language. The potential communicational value of pre-linguistic vocal interactions between human infants and mothers has been studied in the past decades. With 120 dyads (mothers and three- or six-month-old infants), we used the classical Still Face Paradigm (SFP) in which mothers interact freely with their infants, then refrain from communication (Still Face, SF), and finally resume play. We employed innovative automated techniques to measure infant and maternal vocalization and pause, and dyadic parameters (infant response to mother, joint silence and overlap) and the emotional component of Infant Directed Speech (e-IDS) throughout the interaction. We showed that: (i) during the initial free play mothers use longer vocalizations and more e-IDS when they interact with older infants and (ii) infant boys exhibit longer vocalizations and shorter pauses than girls. (iii) During the SF and reunion phases, infants show marked and sustained changes in vocalizations but their mothers do not and (iv) mother–infant dyadic parameters increase in the reunion phase. Our quantitative results show that infants, from the age of three months, actively participate to restore the interactive loop after communicative ruptures long before vocalizations show clear linguistic meaning. Thus, auditory signals provide from early in life a channel by which infants co-create interactions, enhancing the mother–infant bond.

Distinguish self- and hetero-perceived stress through behavioral imaging and physiological features

&NA; Stress reactivity is a complex phenomenon associated to multiple and multimodal expressions. Response to stressors has an obvious survival function and may be seen as an internal regulation to adapt to threat or danger. The intensity of this internal response can be assessed as the self‐perception of the stress response. In species with social organization, this response also serves a communicative function, so‐called hetero‐perception. Our study presents multimodal stress detection assessment ‐ a new methodology combining behavioral imaging and physiological monitoring for analyzing stress from these two perspectives. The system is based on automatic extraction of 39 behavioral (2D + 3D video recording) and 62 physiological (Nexus‐10 recording) features during a socially evaluated mental arithmetic test. The analysis with machine learning techniques for automatic classification using Support Vector Machine (SVM) show that self‐perception and hetero‐perception of social stress are both close but different phenomena: self‐perception was significantly correlated with hetero‐perception but significantly differed from it. Also, assessing stress with SVM through multimodality gave excellent classification results (F1 score values: 0.9 ± 0.012 for hetero‐perception and 0.87 ± 0.021 for self‐perception). In the best selected feature subsets, we found some common behavioral and physiological features that allow classification of both self‐ and hetero‐perceived stress. However, we also found the contributing features for automatic classifications had opposite distributions: self‐perception classification was mainly based on physiological features and hetero‐perception was mainly based on behavioral features. HighlightsWe investigated self‐ and hetero‐perceived stress in 25 young adults during a socially evaluated mental arithmetic test.We present a new methodology combining behavioral imaging and physiological monitoring, with machine learning method to assess social stress and its main components.Self‐perception of social stress (assessed by the subjects themselves) was significantly correlated with hetero‐perception (assessed by external observers)Classification methods allow to associate self perception to mainly physiological features and hetero‐perception to mainly behavioral features.We discuss the implication of the specifics of behavioral and physiological features to support internal perception or inter‐individual communication from an evolutionary perspective.