Family cohesion refers to the emotion, support, helpfulness and caring among family members (Olson, 2011). Adolescence can be considered a sensitive period for social development, with psychological and social cognitive changes (Blakemore & Mills,2014). During adolescence, the social world and the interpersonal interactions become increasingly important. Previous research indicated that family cohesion may help adolescents to overcome the challenges of social interactions by receiving social and emotional supports from family members (Johnson et al., 2001). However, the underlying neural mechanism for the impacts of family cohesion on adolescent-parent emotional interactions has not been fully examined. As a biomarker of social and emotional interaction, the electroencephalogram (EEG) interbrain synchrony may represent the behavioral and emotional synchrony, which reflects the emotional bond within adolescent-parent dyads (Konvalinka & Roepstorff, 2012). Making further exploration of the impacts of family cohesion on the neural synchrony within adolescent-parent dyads during an emotional related task may shed light on the understanding of the biological base of social interaction. Therefore, this study examined the differences in the neural synchrony in response to different emotional stimulus simultaneously between the adolescent-parent dyads who had different level of family cohesion.
Family cohesion is defined as the emotional bonding that family members have toward each other (Olson & Craddock,1980). It is the core component of family functioning. Previous studies indicated that balanced level of family cohesion (e.g., from moderately low to moderately high level) is beneficial and viable for healthy family functioning (Olson, 2011). In a functional and cohesive family, family members can be emotionally connected to, provide support and caring for their families (Starke & Svensson, 2001).
Family cohesion has significant impacts on adolescents’ behavior, socio-emotional development, well-being in their later life, and caregivers’ parenting behaviors (Rahgozar et al., 2012; Behnke et al., 2008). It is highly related to individuals’ positive well-being. For example, adolescents in families with a high level of family cohesion would report more positive emotional experience, more life satisfied, and more meaning and purpose in life (Fosco & Lydon-Staley, 2020). Adverse family processes may operate to increase adolescents' vulnerability to depression (Sheeber et al., 2001). Previous research also indicated that family cohesion is associated with a lower level of negative behavioral outcomes during development (e.g., externalizing behaviors) (Hong et al., 2021). The influence of family cohesion on children and adolescents’ behavioral problems may be moderated by the caregivers’ health condition and parenting behaviors. Family cohesion can provide important emotional support and boding to reduce the negative impacts of the maladaptive parenting behavior on children’s behavioral problems (Leidy et al., 2010). It is considered to be an important protective buffer as it meets the individual’s psychological need for affiliation, security and emotional connection with others (Roth & Brooks-Gunn, 2000).
Not only the positive impacts of adolescents’ behavior and mental health, family cohesion also has the protective impacts on social and emotional interaction for adolescents. Family cohesion is positively correlated with close emotional bonding and depend attachments. A cohesive family reflects a symbiotic and interdependent relationship between family members (Alavi et al., 2020). For example, a child’s mental and emotional status would depend on and be impacted by the other members. Family cohesion is also related to the family member’s feelings (i.e., loneliness), which reflect their family environment and the quality of the interactions with other family members (Johnson et al., 2001). Previous research indicated that family cohesion is negatively correlated with the parent-adolescent conflict (Sui et al., 2015). Higher family cohesion which is characterized as a higher family engagement is negatively correlated with the adolescents’ depressive symptoms, higher levels of family support, and less psychological control from mothers (Starke & Svensson, 2001). Adolescents who grow in a family with moderate cohesion levels would have more positive communication and are more comfortable to be close with other during social interactions. Adolescents with high family cohesion would show better communication skills and feel less anxious and negative experiences during socio-emotional interactions (Olson, 2000). Previous research suggested that family cohesion is positively associated with parental support, responsiveness, and greater positive parent-child engagement. Family members have significantly more contact and communication with one another. It is possible that the family rules in a cohesive family make family members stay more in contact with one another (Reeves et al., 2020). On the contrary, a lack of family cohesion is associated with the negative parent-child interaction which may increase the social stress and reduce emotional support from the parents during social interaction (Hong et al., 2015). Family members with low cohesion would have less involvement in one another’s lives and show less emotional bonding with one another (Olson, 2000).
Adolescence is characterized as the increased independence and the development of self. With the pursuit of independence out of the family environment, adolescents spend more time alone or with their peers, and the conflict affective intensity interactions between adolescents and their parents increases (Steinberg, 1991). As stated above, family cohesion may serve as a protective factor for parent-adolescent conflicts during socio-emotional interactions and seriously influence the effectiveness and quality of parent-adolescent emotional interactions (Johnson et al., 2001). The most important impacts of family cohesion could increase the psychological and emotional bonding between parent-adolescent dyads. During socio-emotional interactions, the behavioral, emotional, physiological and neural synchronization has been considered as an evolutionary adaptive outcome of interpersonal bonding (Hove & Risen, 2009). In this case, when engaging in social situations, family members in a high cohesive family might present a higher level of similarities in behavioral, emotional, physiological and neural levels because of their inherently biological and emotional bonding. However, there is little neural evidences to suggest that the level of family cohesion is associated with neural interbrain synchrony between adolescents and parents during socio-emotional interactions.
As the most important social relationship of each individual, the interaction between infant and caregiver is thought to be the first experience of social interaction. The interbrain synchrony between infant and caregiver in biological rhythms and social signals reflects the inherently biological and emotional bonding, which is also an important feature of the early brain matures (Djalovski et al., 2021). Previous research demonstrated that the moment-to-moment interbrain synchrony is a sensitive maker that can predict dynamic socio-emotional interactions (Dikker et al., 2017). It is likely driven by the shared attention and emotional processing mechanism within the dyads during moments of social contact and communication.
Generally, there are four types of interbrain synchrony, induced synchrony is associated with the phenomenon that two brains tend to be synchronized with the influence of common external stimuli (Burgess, 2013). For instance, two participants will show synchrony without information transmission and interaction, such as viewing a movie (Hasson et al., 2008). According to the phase resetting theory, each individual is sending out conspicuously social signals in the process of social interaction, such as gaze, voice, body posture. As the trigger of neural synchrony, these signals trigger the phase reset of the ongoing neural oscillations of the interacting parties, thus causing the phase difference between the two signal strings to remain constant (Wang et al., 2021). Previous research suggested that the interbrain synchrony, which can be measured by the EEG-based functional connectivity provides a useful tool for studying the simultaneous brain activity between dyads during interactions in different emotional states (Costa et al., 2006). For example, in a study, participants viewed film clips that evoked different emotional states (e.g., neutral, positive, or negative). There was an overall increase of interbrain synchrony during emotional stimulation (e.g., during viewing positive or negative film clips). However, the interbrain synchrony indices were significantly different among emotional states (Lee & Hsieh, 2014). Another study also found that there was a significant difference of hyper-connectivity existed in the gamma frequency band between positive and negative stimulus conditions (Zhu et al., 2018). During social interactions, compared with the negative emotional states, the inter-brain network showed significantly higher strength for positive emotional states for the parent-infant dyads (Santamaria et al., 2020).
This biobehavioral synchrony could be a consequence of the coordination of physiological and behavioral processes when individual and their caregiver engagement in each other’s social life (Djalovski et al., 2021). Increased interbrain synchrony facilitates emotional sharing, social understanding, psychological support, empathy between individual and their caregiver because of the accessibility to each other’s internal state (Wheatley et al., 2012). In this case, such interbrain synchrony could be an important neural indicator of the cohesion level for the family members.
The quality and connection between parent and adolescents during social interaction could reflect the level of family cohesion and family atmosphere. However, little is known about the neural underpinnings about how the level of family cohesion is associated with the interpersonal neural connectivity between adolescents and parents. As mentioned above, induced synchrony could be reflected from the phenomenon that two brains tend to be synchronized with the influence of common external stimuli (Burgess, 2013). Thus, in the current study, the hyperscanning method was used to examine the neural synchrony in response to different emotional film clips between adolescent-parent dyads in different level of family cohesion. Because of the positive impacts of family cohesion on socio-emotional interactions between family members (Konrad, 2016), we hypothesized that high family cohesion parent-adolescent dyads would have high levels of interbrain synchrony in response to emotional film clips. Moreover, previous study demonstrated that the hyper-connectivity (e.g., in the gamma frequency band) in the positive stimulation condition was greater than in the negative stimulation condition (Zhu et al., 2018). We hypothesized that how the level of family cohesion associated with the interbrain synchrony between adolescents and parents would be different in the positive and negative emotional conditions.