Real-Time Mobile EEG Hyperscanning: A Precise and Accessible Platform for Social Brain-Computer Interfaces

This paper presents a cost-effective fully mobile EEG platform for reliable synchronous multi-brain imaging (hyperscanning) for social human-machine interactions, designed for both online and offline applications. We first quantify the error introduced when Lab Streaming Layer (LSL) is used as primary synchronization method on off-the-shelf mobile EEG systems: sampling-rate drifts and software latencies render conventional wireless hyperscanning techniques unreliable. To overcome these limitations, we introduce a novel wireless hardware-trigger synchronization approach based on sub-1GHz technology with a customized acquisition software, leveraging affordable commercial wireless EEG (OpenBCI Cyton system) to achieve near-zero phase-delay synchronization while maintaining full mobility. The integrated hardware-software stack reduces online inter-device jitter to more than 1/10 of the original observed jitter, yielding a 99.3% of accuracy in phaselocking value and spectral coherence during online measurement of synthetic 30 Hz signals. A mobile hyperscanning study on interpersonal behavioral synchronization (N = 8) validates ecological performance: significant inter-brain coupling was observed only during well-synchronized steps (p < 0.05, FWER-corrected). Finally, we demonstrate real-time visualization of inter-brain coupling using customized version of Vizaj, an open-source spatial networks visualization tool, confirming suitability for live neurofeedback. The proposed synchronization platform costs under $100 for two heads, requires no cables between participants, and is readily adaptable to OpenBCI hardware. By releasing reproducible designs and code, this work lowers the barrier to group-level neurotechnology and paves the way for social brain-computer interfaces.