Integration of social status and trust through interpersonal brain synchronization

Quantification of inter-brain coupling: A review of current methods used in haemodynamic and electrophysiological hyperscanning studies

Hyperscanning is a form of neuroimaging experiment where the brains of two or more participants are imaged simultaneously whilst they interact. Within the domain of social neuroscience, hyperscanning is increasingly used to measure inter-brain coupling (IBC) and explore how brain responses change in tandem during social interaction. In addition to cognitive research, some have suggested that quantification of the interplay between interacting participants can be used as a biomarker for a variety of cognitive mechanisms aswell as to investigate mental health and developmental conditions including schizophrenia, social anxiety and autism. However, many different methods have been used to quantify brain coupling and this can lead to questions about comparability across studies and reduce research reproducibility. Here, we review methods for quantifying IBC, and suggest some ways moving forward. Following the PRISMA guidelines, we reviewed 215 hyperscanning studies, across four different brain imaging modalities: functional near-infrared spectroscopy (fNIRS), functional magnetic resonance (fMRI), electroencephalography (EEG) and magnetoencephalography (MEG). Overall, the review identified a total of 27 different methods used to compute IBC. The most common hyperscanning modality is fNIRS, used by 119 studies, 89 of which adopted wavelet coherence. Based on the results of this literature survey, we first report summary statistics of the hyperscanning field, followed by a brief overview of each signal that is obtained from each neuroimaging modality used in hyperscanning. We then discuss the rationale, assumptions and suitability of each method to different modalities which can be used to investigate IBC. Finally, we discuss issues surrounding the interpretation of each method.

Verbal information exchange enhances collective performance through increasing group identification

Information exchange is a key factor in the attainment of collective outcomes and the navigation of social life. In the current study, we investigated whether and how information exchange enhanced collective performance by combining behavioral and neuroimaging approaches from the perspective of multiparticipant neuroscience. To evaluate collective performance, we measured the collaborative problem-solving abilities of triads working on a murder mystery case. We first found that verbal information exchange significantly enhanced collective performance compared to nonverbal exchange. Moreover, both group sharing and group discussion positively contributed to this effect, with group discussion being more essential. Importantly, group identification mediated the positive effect of verbal information exchange on collective performance. This mediation was supported by higher interactive frequency and enhanced within-group neural synchronization (GNS) in the dorsolateral prefrontal cortex (DLPFC). Taken together, we provided a multiparticipant theoretical model to explain how verbal information exchange enhanced collective performance. Our findings deepen the insight into the workings of group decision-making.

A Brain-To-Brain Mechanism for Social Transmission of Threat Learning

Survival and adaptation in environments require swift and efficacious learning about what is dangerous. Across species, much of such threat learning is acquired socially, e.g., through the observation of others' ("demonstrators'") defensive behaviors. However, the specific neural mechanisms responsible for the integration of information shared between demonstrators and observers remain largely unknown. This dearth of knowledge is addressed by performing magnetoencephalography (MEG) neuroimaging in demonstrator-observer dyads. A set of stimuli are first shown to a demonstrator whose defensive responses are filmed and later presented to an observer, while neuronal activity is recorded sequentially from both individuals who never interacted directly. These results show that brain-to-brain coupling (BtBC) in the fronto-limbic circuit (including insula, ventromedial, and dorsolateral prefrontal cortex) within demonstrator-observer dyads predict subsequent expressions of learning in the observer. Importantly, the predictive power of BtBC magnifies when a threat is imminent to the demonstrator. Furthermore, BtBC depends on how observers perceive their social status relative to the demonstrator, likely driven by shared attention and emotion, as bolstered by dyadic pupillary coupling. Taken together, this study describes a brain-to-brain mechanism for social threat learning, involving BtBC, which reflects social relationships and predicts adaptive, learned behaviors.

Does rDLPFC activity alter trust? Evidence from a tDCS study

Trust plays an important role in the human economy and people's social lives. Trust is affected by various factors and is related to many brain regions, such as the dorsolateral prefrontal cortex (DLPFC). However, few studies have focused on the impact of the DLPFC on trust through transcranial direct current stimulation (tDCS), although abundant psychology and neuroscience studies have theoretically discussed the possible link between DLPFC activity and trust. In the present study, we aimed to provide evidence of a causal relationship between the rDLPFC and trust behavior by conducting multiple rounds of the classical trust game and applying tDCS over the rDLPFC. We found that overall, anodal stimulation increased trust compared with cathodal stimulation and sham stimulation, while the results in different stages were not completely the same. Our work indicates a causal relationship between rDLPFC excitability and trust behavior and provides a new direction for future research.

Brain-to-brain synchrony during dyadic action co-representation under acute stress: evidence from fNIRS-based hyperscanning

Unexpected acute stressors may affect our co-representation with other co-actors when completing the joint tasks. The present study adopted the emergent functional near-infrared spectroscopy (fNIRS)-based hyperscanning method to explore the brain-to-brain synchrony when implementing the Joint Simon Task under acute stress induced in the laboratory. The behavioral results reported that the joint Simon effect (JSE) was found in both the stress group and the control group, but the joint Simon effect in the stress group was significantly lessened than the joint Simon effect in the control group, demonstrating that when completing the joint action task in the state of acute stress, women's ability to distinguishing self- from other-related mental representations was improved, and the strength of women's action co-representation was diminished. The fNIRS results showed that when completing the joint Simon task in the state of the acute stress, the brain-to-brain synchrony at the r-TPJ in the stress group was significantly higher than that in the control group, demonstrating that the increased brain-to-brain synchrony at the TPJ may be served as the critical brain-to-brain neural mechanism underlying the joint action task under acute stress.

Why people engage in corrupt collaboration: an observation at the multi-brain level

Recent studies suggest that corrupt collaboration (i.e. acquiring private benefits with joint immoral acts) represents a dilemma between the honesty and reciprocity norms. In this study, we asked pairs of participants (labeled as A and B) to individually toss a coin and report their outcomes; their collective benefit could be maximized by dishonestly reporting (a corrupt behavior). As expected, the likelihood of corrupt behavior was high; this probability was negatively correlated with player A's moral judgment ability but positively correlated with player B's empathic concern (EC). Functional near-infrared spectroscopy data revealed that the brain-to-brain synchronization in the right dorsolateral prefrontal cortex was associated with fewer corrupt behaviors, and that it mediated the relationship between player A's moral judgment ability and corrupt collaboration. Meanwhile, the right temporal-parietal junction synchronization was associated with more corrupt behaviors, and that it mediated the relationship between player B's EC and corrupt collaboration. The roles of these 2 regions are interpreted according to the influence of the honesty and reciprocity norms on corrupt collaboration. In our opinion, these findings provide insight into the underlying mechanisms and modulating factors of corrupt collaboration.

Distinct inter-brain synchronization patterns underlying group decision-making under uncertainty with partners in different interpersonal relationships

Humans may behave in different manners when making decisions with friends and strangers. Whether the interpersonal relationship and the characteristics of the individuals in the group affected the group decision-making under uncertainty in the real-time interaction remains unknown. Using the turn-based Balloon Analogue Risk Task (BART), the present study examined the group decision-making propensity under uncertainty with partners in different interpersonal relationships and interpersonal orientations. Corresponding inter-brain synchronization (IBS) patterns at the prefrontal cortex (PFC) were also uncovered with the fNIRS-based hyperscanning approach. Behavioral results identified that dyads in the friend group exhibited the uncertainty-averse propensity when comparing with the stranger group. The fNIRS results reported that feedback-related IBS at the left inferior frontal gyrus (l-IFG) and medial frontopolar cortex (mFPC) during different feedbacks was modulated by interpersonal relationships. The IBS at all channels in the PFC during the positive and negative feedbacks, respectively, predicted the decision-making propensity under uncertainty in the stranger and friend groups based on the support vector machine (SVM) algorithm. The moderating role of the social value orientation (SVO) was also verified in the mediation effect of the dyad closeness on the decision-making propensity under uncertainty via the IBS at the right lateral frontopolar cortex (r-FPC). These findings demonstrated disparate behavioral responses and inter-brain synchronization patterns underlying group decision-making under uncertainty with partners in different interpersonal relationships.

The single- and dual-brain mechanisms underlying the adviser's confidence expression strategy switching during influence management

Effective influence management during advice-giving requires individuals to express confidence in the advice properly and switch timely between the 'competitive' strategy and the 'defensive' strategy. However, how advisers switch between these two strategies, and whether and why there exist individual differences during this process remain elusive. We used an advice-giving game that manipulated incentive contexts (Incentivized/Non-Incentivized) to induce the adviser's confidence expression strategy switching and measured the brain activities of adviser and advisee concurrently using functional near-infrared spectroscopy (fNIRS). Behaviorally, we observed individual differences in strategy switching. Some advisers applied the 'defensive' strategy when incentivized and the 'competitive' strategy when not incentivized, while others applied the 'competitive' strategy when incentivized and the 'defensive' strategy when not incentivized. This effect was mediated by the adviser's perceived stress in each condition and was reflected by the frequencies of advice-taking in the advisees. Neurally, brain activation in the dorsolateral prefrontal cortex (DLPFC) supported strategy switching, as well as interpersonal neural synchronization (INS) in the temporoparietal junction (TPJ) that supported influence management. This two-in-one process, i.e., confidence expression strategy switching and the corresponding influence management, was linked and modulated by the strength of DLPFC-TPJ functional connectivity in the adviser. We further developed a descriptive model that contributed to understanding the adviser's strategy switching during influence management.

A study of trust behavior and its neural basis in athletes under long-term exercise training

Previous research has suggested that long-term exercise training can influence trusting behaviors, but the supporting evidence is limited. Therefore, exploring inter-athlete trust behaviors and its neural mechanism could better answer the potential association between athletic training and trust behaviors. Accordingly, the present study used a trust game (TG) task to assess interpersonal trust behavior in the sex-specific athlete group and the ordinary college group; and a functional near-infrared spectroscopy (fNIRS) hyperscanning technology was used to capture the interpersonal neural synchronization (INS) in brain regions of interest to the dyads. The results showed that the athlete group had significantly higher trust behaviors and significantly higher INS in the left frontal pole and left dorsolateral prefrontal than the college group; male athletes had significantly higher trust behaviors and significantly higher INS in the left dorsolateral prefrontal than female athletes. This study suggests that athletes have better trusting behaviors and that this advantage may be related to enhanced INS in the left dorsolateral prefrontal lobe.

Three heads are better than one: cooperative learning brains wire together when a consensus is reached

Theories of human learning converge on the view that individuals working together learn better than do those working independently. Little is known, however, about the neural mechanisms of learning through cooperation. We addressed this research gap by leveraging functional near-infrared spectroscopy to record the brain activity of triad members in a group simultaneously. Triads were instructed to analyze an ancient Chinese poem either cooperatively or independently. Four main findings emerged. First, we observed significant within-group neural synchronization (GNS) in the left superior temporal cortex, supramarginal gyrus, and postcentral gyrus during cooperative learning compared with independent learning. Second, the enhancement of GNS in triads was amplified when a consensus was reached (vs. elaboration or argument) during cooperative learning. Third, GNS was predictive of learning outcome at an early stage (156-170 s after learning was initiated). Fourth, social factors such as social closeness (e.g. how much learners liked one other) were reflected in GNS and co-varied with learning engagement. These results provide neuroscientific support for Piaget's theory of cognitive development and favor the notion that successful learning through cooperation involves dynamic consensus-building, which is captured in neural patterns shared across learners in a group.

Persuader-receiver neural coupling underlies persuasive messaging and predicts persuasion outcome

Opportunities to persuade and be persuaded are ubiquitous. What interpersonal neural pathway in real-world settings determining successful information propagation in naturalistic two-person persuasion scenarios? Hereby, we extended prior research on a naturalistic dyadic persuasion paradigm (NDP) using dual-fNIRS protocol simultaneously measured the neural activity from persuader-receiver dyads while they engaged in a modified "Arctic Survival Task." Investigating whether neural coupling between persuaders and receivers underpinning of persuading and predict persuasion outcomes (i.e., receiver's compliance). Broadly, we indicated that the persuasive arguments increase neural coupling significantly compared to non-persuasive arguments in the left superior temporal gyrus-superior frontal gyrus and superior frontal gyrus-inferior frontal gyrus. G-causality indices further revealed the coupling directionality of information flows between the persuader and receiver. Critically, the neural coupling could be a better predictor of persuasion outcomes relative to traditional self-report measures. Eventually, temporal dynamics neural coupling incorporating video recording revealed neural coupling marked the micro-level processes in response to persuading messages and possibly reflecting the time that persuasion might occurs. The initial case of the arguments with targeted views is valuable as the first step in encouraging the receiver's compliance. Our investigation represented an innovative interpersonal approach toward comprehending the neuroscience and psychology underlying complex and true persuasion.

Group polarization calls for group-level brain communication

Group of people shows the shift towards extreme of decision-making as opposed to individuals. Previous studies have revealed two directions of group polarization, i.e., risky shift and cautious shift, but how group of brains drive these shifts remains unknown. In the current study, we arranged risk advantage and disadvantage situations to elicit group polarization of risky shift and cautious shift respectively, and examined the averaged inter-brain synchronization (ABS) among participant triads during group decision making versus individual decision making. The elicited group polarizations were accompanied by the enhanced ABS at bilateral prefrontal areas and left temporoparietal junction (TPJ). Specifically, the TPJ ABS was equivalent in risky shift and cautious shift, and based on machine learning analyses, could predict the extent of group polarization; for two shifts, it negatively correlated with negative emotion. However, the right prefrontal ABS was stronger in risky shift than in cautious shift, and the same area showed the larger brain deactivation in former shift, indicating weaker executive control. For the left prefrontal ABS, only the equivalent ABS was found for two shifts. In sum, group polarization of risky shift and cautious shift calls for inter-brain communication at the group level, and the former shift is with deactivation and more brain synchronization. Our study suggests emotional and cognitive adjustment in decision making of the group compared with individuals.

Neural and behavioral alterations of a real-time interpersonal distance (IPD) development process in differing social status interactions

Background

Evidence showed neural changes in interpersonal distance (IPD) interaction, and neural activities are affected by relationships (such as friends or strangers). Behavior studies proved that social status strongly affects IPD between two persons. However, how the differing social status impacts neural alterations in the IPD interactions remains unknown.

Objectives

The teacher-student relationship is a typical representation of the difference in social status. The present study aims to investigate the IPD performance and brain processes underlying real-time differing social status during the development process from teacher-student interactions.

Materials and methods

We designed three within-subject experiments corresponding to the inclusion, control, and affection stages of IPD. Altogether, 38 valid healthy participants participated in three experiments with a teacher (differing social status condition, DS condition) and a peer student (peer social status condition, PS condition) separately. This study employed functional near-infrared spectroscopy (fNIRS) and modified real-time stop-distance paradigms to record IPD performance and neural processes.

Results

For IPD performance, significantly larger IPD gaps were shown in the DS condition than in the PS condition, and IPD feedback affected IPD performance. For neural alterations, activated frontopolar area (FPA, BA10), dorsolateral prefrontal cortex (DLPFC, BA9/BA46), and Broca’s area (BA45) were observed across the IPD stages. Importantly, brain activation shifts with the development of IPD. In addition, results showed that differences in Oxy-Hb changes were located in the FPA (BA10), DLPFC (BA9/BA46), and Broca’s area (BA45) between the DS and PS conditions across IPD stages. Additionally, negative correlations were found between Oxy-Hb changes and IPD performance.

Conclusion

We propose prefrontal cortex (PFC) and Broca’s area involvement in IPD interactions, initially focusing on evaluation and action periods, and later on IPD-evaluation processes after feedback. In addition, a difference in Oxy-Hb activities implies the complexity of relationships and social status in IPD interactions.

Dual-MEG interbrain synchronization during turn-taking verbal interactions between mothers and children

Verbal interaction and imitation are essential for language learning and development in young children. However, it is unclear how mother-child dyads synchronize oscillatory neural activity at the cortical level in turn-based speech interactions. Our study investigated interbrain synchrony in mother-child pairs during a turn-taking paradigm of verbal imitation. A dual-MEG (magnetoencephalography) setup was used to measure brain activity from interactive mother-child pairs simultaneously. Interpersonal neural synchronization was compared between socially interactive and noninteractive tasks (passive listening to pure tones). Interbrain networks showed increased synchronization during the socially interactive compared to noninteractive conditions in the theta and alpha bands. Enhanced interpersonal brain synchrony was observed in the right angular gyrus, right triangular, and left opercular parts of the inferior frontal gyrus. Moreover, these parietal and frontal regions appear to be the cortical hubs exhibiting a high number of interbrain connections. These cortical areas could serve as a neural marker for the interactive component in verbal social communication. The present study is the first to investigate mother-child interbrain neural synchronization during verbal social interactions using a dual-MEG setup. Our results advance our understanding of turn-taking during verbal interaction between mother-child dyads and suggest a role for social "gating" in language learning.

Nonverbal synchrony in subjects with hearing impairment and their significant others

Introduction

Hearing loss has a great impact on the people affected, their close partner and the interaction between both, as oral communication is restricted. Nonverbal communication, which expresses emotions and includes implicit information on interpersonal relationship, has rarely been studied in people with hearing impairment (PHI). In psychological settings, non-verbal synchrony of body movements in dyads is a reliable method to study interpersonal relationship.

Material and methods

A 10-min social interaction was videorecorded in 39 PHI (29 spouses and 10 parent-child dyads) and their significant others (SOs). Nonverbal synchrony, which means the nonverbal behaviors of two interacting persons (referring to both general synchrony and the role of leading) and verbal interaction (percentage of speech, frequency of repetitions, and queries) were analyzed by computer algorithms and observer ratings. Hearing-related quality of life, coping mechanisms, general psychopathology, quality of relationship, and burden of hearing loss experienced by SOs were assessed using questionnaires.

Results

In the 39 dyads, true nonverbal synchrony differed from pseudosynchrony [t_(43.4) = 2.41; p = 0.02] with a medium effect size (d = 0.42). Gender of PHI had a significant effect on general synchrony (p = 0.025) and on leading by SOs (p = 0.017). Age gap correlated with synchronic movements (p = 0.047). Very short duration of hearing impairment was associated with lower nonverbal synchrony in the role of leading by SOs (p = 0.031). Feeling of closeness by PHI correlated negatively with the role of leading by SOs (p > 0.001) and feeling of closeness by SOs was positively associated with leading by PHI (p = 0.015). No correlation was detected between nonverbal synchrony and other questionnaires. Burden experienced by the SOs was higher in SOs who reported less closeness (p = 0.014).

Discussion

A longer hearing impairment leads to more nonverbal leading by SOs compared to PHI with very short duration of hearing loss, possibly because of the long-lasting imbalance in communication. If PHI felt more closeness, SOs led less and vice versa. Burden experienced by SOs negatively correlated with closeness reported by SOs. Use of nonverbal signals and communication might help to improve benefits of auditory rehabilitation for PHI and decrease burden experienced by SOs.