# Investigating interbrain synchrony under teamwork disruption: an fNIRS hyperscanning study

## TL;DR

This study explores whether brain activity synchronization between team members changes when teamwork is disrupted, finding that it remains stable despite changes in task difficulty.

## Contribution

The study challenges the idea that interbrain synchrony is a reactive marker of teamwork by showing it remains unchanged during disruptions.

## Key findings

- Interbrain synchrony did not change when teamwork was disrupted by increased task difficulty.
- Teamwork adaptation was observed in communication but not in interbrain synchrony.
- Findings suggest interbrain synchrony may reflect a stable rather than reactive team state.

## Abstract

Teams are inherently adaptive entities that continuously adapt to changes or disruptions in their tasks or environments. During collaboration, interbrain synchrony (IBS) emerges, reflecting the temporal alignment of neural activity between team members. Building on this, IBS has been proposed as a potential marker of teamwork, suggesting that IBS should be sensitive to changes in teamwork.

The present study investigated whether IBS is sensitive to changes in teamwork. We hypothesized that disruptions in teamwork would be accompanied by alterations in IBS dynamics.

Ninety-eight healthy adults (mean age = 22.5 ± 3.22 years; 69 females, 65.1%) were assigned to forty-nine dyads. Each pair completed a 20-minute computer-based navigation task while their brain activity was simultaneously recorded using fNIRS hyperscanning. Dyads in the experimental group encountered an unexpected increase in task difficulty midway through the task, whereas those in the control group completed the task without disruption. We examined three features of IBS - its overall level, temporal slope trajectory, and the temporal recurrence patterns.

Control analyses confirmed that IBS reliably emerged during the task (χ²(1) = 50.24, p < .001) and that the experimental manipulation successfully disrupted teamwork, as reflected in altered team behavioral responses in communication (χ²(1) = 8.48, p = 0.004) and performance (χ²(1) = 24.99, p < .001). Nevertheless, no evidence was found for disruption-related changes in IBS across the three features examined (all Time x Group interactions p > .05.

These findings raise the possibility that IBS may reflect a stable collective state rather than a reactive one, thereby challenging its interpretation as a direct marker of teamwork. Methodological considerations, including the operationalization of IBS, are also discussed as potential explanations for the lack of observed change in IBS.

The online version contains supplementary material available at 10.1186/s12993-026-00320-6.

A sudden increase in task difficulty was used to disrupt teamwork.Three interbrain synchrony features (level, slope, %DET) were used to assess temporal dynamics.Interbrain synchrony remained unchanged despite teamwork disruption.Teamwork adaptation was observed in communication but not in interbrain synchrony.Findings question whether interbrain synchrony reflects reactive or stable team state.

A sudden increase in task difficulty was used to disrupt teamwork.

Three interbrain synchrony features (level, slope, %DET) were used to assess temporal dynamics.

Interbrain synchrony remained unchanged despite teamwork disruption.

Teamwork adaptation was observed in communication but not in interbrain synchrony.

Findings question whether interbrain synchrony reflects reactive or stable team state.

The online version contains supplementary material available at 10.1186/s12993-026-00320-6.