Conditions for Inter-brain Synchronization in Remote Communication: Investigating the Role of Transmission Delay

TL;DR

This study investigates how transmission delay affects inter-brain synchronization (IBS) during remote communication using EEG hyperscanning and Phase Locking Value (PLV). The authors compare face-to-face and remote conditions with controlled delays (0–600 ms), applying permutation tests and Kruskal–Wallis analyses to assess IBS in alpha and beta bands across 64 channel pairs. They find that IBS persists at low remote delays (0–300 ms) but significantly diminishes at delays ≥450 ms, with distinct spatial patterns in alpha and beta bands. The findings suggest IBS as an objective index of remote communication quality and highlight the critical latency threshold for preserving neural coupling, offering practical guidance for latency management in remote collaboration systems.

Abstract

Inter-brain synchronization (IBS), the alignment of neural activities between individuals, is a fundamental mechanism underlying effective social interactions and communication. Prior research has demonstrated that IBS can occur during collaborative tasks and is deeply connected to communication effectiveness. Building on these findings, recent investigations reveal that IBS happens during remote interactions, implying that brain activities between individuals can synchronize despite latency and physical separation. However, the conditions under which this synchronization occurs or is disrupted in remote settings, especially the effect of latency, are not fully understood. This study investigates how varying transmission latency affects IBS, in order to identify thresholds where synchronization is disrupted. Using electroencephalography measurements quantified through Phase Locking Value -- a metric that captures synchronization between brainwave phases -- we first confirm synchronization under face-to-face conditions and then observe changes in IBS across remote communication scenarios. Our findings reveal that IBS can occur during remote collaboration, but is critically dependent on transmission delays, with delays exceeding 450 ms significantly disrupting synchronization. These findings suggest that IBS may serve as a key indicator of communication quality in remote interactions, offering insights for improving remote communication systems and collaboration.

Figures (8)

• Figure 1: The environment setups: (A) Participants communicated from separate rooms in the remote communication setting. (B) Participants communicated face-to-face. (C) During rest sessions, participants did not communicate and could not see each other.
• Figure 2: Experiment during remote condition.
• Figure 3: To measure the audio delay in OBS, we play a beep sound from an external device (e.g., a smartphone) and capture it through an audio interface. The captured signal is replayed via OBS, and we calculate the delay between the timestamp of the original beep sound and its output from OBS.
• Figure 4: To quantify video delay in OBS, we configure the OBS window to display the camera feed and quickly move a marker in front of the camera. The captured movement is processed and replayed via OBS. To measure the delay, we use a secondary camera to record both the original movement and the OBS playback, then compute the time difference between the timestamps of the original action and its OBS output.
• Figure 5: The position of electrodes: The device has 8 electrodes evenly distributed on the scalp.