Introduction: Within a shared decision-making process, persuasion dynamics develop as a communication sub-process that can be characterized by different phases. This study examines hemodynamic functional Near-Infrared Spectroscopy (fNIRS) coherence measures in dyads of decision-makers. The interaction occurs in two phases: Phase 1, where the persuader (Pr) introduces the decision topic and uses persuasive strategies, and Phase 2, where the Persuaded (Pd) responds and may agree with the Pr’s selected option. Method: Fourteen dyads participated, with fNIRS measuring oxygenated (O₂Hb) and deoxygenated (HHb) hemoglobin concentration changes in the prefrontal cortex (PFC) during both phases. Hemodynamic coherence within dyads was explored through the computation of a dissimilarity index (Euclidean distance). Results: Phase 2 showed increased HHb dissimilarity, indicating greater divergence in brain activity during the Pd’s response phase. Discussion: These findings suggest that, during persuasion, when Pd responds, there is increased dissimilarity in cognitive and neural processes, without implying a loss of synergy. The study highlights the importance of interactional dynamics in shaping decision outcomes and underscores the potential of fNIRS as a non-invasive tool for monitoring brain activity in clinical and collaborative settings.

This hyperscanning study explores the central (hemodynamic) and peripheral (autonomic) markers of persuasion within a shared decision-making process. Decision-making was examined through a task where two decision-makers assumed the role of Persuader (P-der) and Persuaded (P-ded), with the P-der aiming to increase group decision orientation in the P-ded. Data were collected from 14 dyads using functional near-infrared spectroscopy to measure prefrontal cortex (PFC) hemodynamic activity and collection and recording of autonomic indices including heart rate (HR) and HR variability (HRV). The analysis focused on two phases: Phase 1, where the P-der presented the scenario and enacted their persuasive strategy, and Phase 2, characterized by the P-ded’s response. The results revealed significant effects on the dissimilarity indices at the dyadic level. Compared with Phase 1, Phase 2 included higher oxygenated hemoglobin dissimilarity in the PFC, indicating greater inter-dyadic divergence during the P-ded’s response. HR dissimilarity increased when the P-ded spoke, suggesting disrupted synergy, while HRV dissimilarity was higher when the P-der spoke, potentially reflecting differences in stress regulation. These findings suggest that neurophysiological coherence varies based on persuasion phases within shared decision-making, with P-ded introducing greater dissonance in dyads synergy. Compared with single-subject approaches, dyadic analyses offer a more accurate understanding of the interpersonal nature of persuasion dynamics during decision-making.

Background: Decision-making is often a shared and collective process, facilitated by negotiation dynamics. This study adopted fNIRS hyperscanning to explore similar brain hemodynamic responses during naturalistic negotiation and decision-making interactions and the role of individual differences. Methods: Homologous dyads of speaker A and speaker B engaged in a realistic negotiation task, deciding how to handle a non-conforming team member. The task included three steps: the Individual step (Indstep), where the participants individually selected how to decide; the Cooperation step (Coopstep), involving collaborative negotiation; and the Agreement step (Agrstep), where a mutual agreement was reached. General Decision-Making Style (GDMS), Maximization Scale (MS) and Big Five Inventory (BFI-10) were also administered. Results: Higher deoxygenated hemoglobin (HHb) dissimilarity emerged when speaker B was speaking and speaker A was listening, suggesting that the members exhibited differences in the level of cognitive demand required for the conversation, or that speaker A was attempting to assert his perspective. Moreover, the avoidant decision-making style, the alternative-search tendency, and the decision-making difficulties subscales negatively correlated with HHb dissimilarity in the left hemisphere during the Agrstep, as well as the extraversion trait during the Indstep and the Coopstep, highlighting how individual differences modulate the neural mechanisms underlying negotiation. Conclusions: These findings reveal that brain patterns of neural similarity in negotiation contexts are sensitive to both conversational roles and individual decision-making profiles. Integrating a hyperscanning paradigm with psychological assessment offers interesting insights into the neurocognitive foundations of cooperation, revealing the influence of cognitive and personality traits on neural activity associated with the naturalistic negotiation process.