# Electrophysiological Hyperscanning of Negotiation During Group-Oriented Decision-Making
## 1 Introduction
Although the importance of studying brain dynamics during real-time social interactions is widely acknowledged, most research has measured the electrophysiological (EEG) brain activity in single subjects rather than in interacting pairs or groups [19]. Regarding the functional significance of EEG frequency bands, delta waves are thought to signal novelty in emotional contexts, responding more to a stimulus's attentional salience than its emotional content [20]. Theta activity has been linked to motivation, emotional processing, task relevance [20], and adaptive behavior in social negotiation [21]. Alpha and beta bands indicate cognitive effort, attention, and engagement in decision-making processes [22], with alpha suppression playing a key role in decision-making by reflecting cognitive resource allocation [23]. Beta waves are associated with emotional significance, attentional control, and cognitive regulation [24; 25]. Gamma oscillations integrate sensory and emotional processing and are markers of top-down attention and conscious awareness [26; 27]. Both beta and gamma bands also play a role in memory and decision-making processes [28]. Also, the specific localization of EEG frequency bands correlate with different neural functions: frontal delta activity is linked to emotional and motivational processing [29; 20], while theta waves in frontal regions reflect attentional engagement and strategic control [21; 30]. Reduced parietal alpha activity is associated with enhanced cognitive performance [30], and parietal-occipital beta waves indicate focused attention [31]. Moreover, alpha and beta bands in parieto-occipital areas are associated with neural correlates of sense of agency, defined as the subjective experience of initiating and controlling actions to affect external events [32] as well as index of working-memory performance [33]. Gamma modulations in parieto-occipital regions, instead, may be interpreted as top-down activation of mental representations and the maintenance of auditory and visual information in working memory. This could reflect the increasing cognitive resources required for more effective planning, as previously evidenced [34; 35]. While single-brain approaches help localize neural activations related to social processes, they fail to grasp the real-time brain-to-brain dynamics. In this field, the hyperscanning paradigm, which enables the simultaneous recording of brain activity from multiple individuals, may reveal functional connections and interbrain synchronization. This approach shifts the focus from isolated brain activity to dynamic interactions, where behaviors and neural patterns continuously adapt to each other. Hyperscanning research has demonstrated the critical role of interbrain synchrony in joint attention, communication, coordination [36; 37; 38], cooperation [37], prosocial exchange [38] and decision-making tasks. In particular, hyperscanning studies have shown that the dorsolateral prefrontal cortex, specifically in the left side, is a key area of cooperation processes [37] as well as the prefrontal cortex, which is implicated in joint action performance [39]. Moreover, during joint actions in cooperative behavior, a higher synchronization was reported in the delta and theta low frequency bands, as an index of social competencies, empathy, and emotional engagement [39]. Additionally, the temporoparietal junction (TPI) is involved in social cognition, including perspective-taking, Theory of Mind, and communication [40]. TPI also plays a role in managing social dynamics, including negotiation processes [41; 42]. However, for a comprehensive understanding of cooperative processes, it is essential to consider real, dynamic interactions where partners are actively engaged, as social exchanges naturally occur in face-to-face settings [39].