The functional signature of decision making across dyads during a persuasive scenario: hemodynamic fNIRS coherence measure

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.