Current needs and future directions of functional near-infrared spectroscopy (fNIRS) hyperscanning for social interaction research

Hyperscanning, the simultaneous recording of multiple brains during social interaction, is an emerging method in social neuroscience. Among available techniques, functional near-infrared spectroscopy (fNIRS) is particularly promising for studies outside laboratory environments. fNIRS hyperscanning presents opportunities and challenges in key domains including data processing, the quantification and interpretation of inter-brain synchrony, and increasing interest in multimodal approaches. To assess the field’s current status and trajectory, we developed a questionnaire for fNIRS hyperscanning researchers, addressing both best practices (“what has been done”) and future priorities (“what ought to be done”). Survey responses were compared with the empirical literature to identify unmet needs, align community perspectives, and chart a course for the field’s progression. Findings showed (i) broad agreement on preprocessing workflows, (ii) widespread use of wavelet transform coherence to quantify inter-brain synchrony, and (iii) growing enthusiasm—and a rapidly expanding pool of datasets—for multimodal recording. Meanwhile, (iv) systematic training in fNIRS hyperscanning is largely absent from university curricula, (v) theoretical frameworks for interpreting neural synchrony remain underdeveloped, and (vi) methodological pipelines integrating multimodal behavioral and neural signals are still lacking. By linking survey insights with existing literature, we highlight solutions and propose concrete steps for advancing fNIRS hyperscanning research.