Résumé
Abstract Background 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. Purpose 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. Methods 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. Results 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. Conclusion 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.