Team Flow Is a Unique Brain State Associated with Enhanced Information Integration and Interbrain Synchrony

Behavioral establishment of team flow. A, Diagram of the finger-tapping music rhythm game. Participants must tap when animated cues moving from the top of the screen reach the tapping area. B, Manipulations: team flow is predicted when the participants are playing the unmodified song and they can see the partner’s positive feedback (Team Flow). The flow state is disrupted through scrambling the music (Team Only). Team interaction is disrupted by hiding the partner’s positive feedback using an occlusion board (Flow Only). See Table 1 for details. C, Sequence of the trials, showing which song and condition per trial was assigned during the main experiment. D, Trial analysis: participants were sitting still while listening to a background music during the resting phase and played the game in the playing phase. The electroencephalogram was epoched for objective assessment of flow i.e., the AEP analysis of the task-irrelevant beeps (orange bar) and for the NCs analysis (green bar). After each trial, participants answered the questionnaire for the subjective assessment of flow. Extended Data Figure 1-1 shows detailed analysis pipeline.

Assessment of the flow state. A–C, Subjective assessment of flow: psychometric rating indices as a measure of subjective flow (flow index; A), team interaction (team index; B), or team flow (team flow index; C) experiences (Extended Data Fig. 2-1 shows the detailed psychometric ratings for each question). Friedman test with Conover’s post hoc test; *p < 0.05, **p < 0.01, ***p < 0.001. Error bars represent mean ± SEM; n = 15. D, E, Objective assessment of flow. D, The mean AEP calculated by averaging the following time windows: N1 (110–150 ms), P1 (210–250 ms), and N2 (310–350 ms), considering polarity. The non-flow condition (Team Only) showed statistically significant higher AEP than the flow conditions. One-way repeated measures ANOVA with Bonferroni post hoc test; *p < 0.05. Error bars represent mean ± SEM; n = 15. E, Spearman’s correlation between AEP and flow index. AEP is negatively correlated with the flow index in the team flow condition (Spearman’s Rho = −0.48, p = 0.03), showing a negative correlation trend in the flow only condition (Spearman’s Rho = −0.29, p = 0.22), and no correlation in the team only condition (Spearman’s Rho = 0.11, p = 0.64). The lines indicate the regression lines. Shaded areas indicate a 95% confidence interval; n = 20. Extended Data Figure 2-2 shows the detailed AEP analysis.

Higher β-γ power at the L-MTC revealed as a unique neural signature for team flow. A, The topographies of the β and γ frequencies (13–120 Hz) computed as the average over normalized power. B, Permutation statistical significance across conditions with Bonferroni multiple comparison corrections. The black crosses indicate channels with p < 0.05. C, The normalized power spectral analysis averaged from the four channels in the left temporal area identified in B. Shaded area represent mean ± SEM; n = 20. Extended Data Figure 3-1 shows the power difference spectral analysis grand averaged across all the 128 channels. D, Averaged normalized power for the β-γ (13–50 Hz) frequency band showing power enhancement in the team flow condition. One-way repeated measures ANOVA with Bonferroni post hoc test; *p < 0.05. Error bars represent mean ± SEM; n = 15. E, The brain regions (highlighted in green), as defined by the Destrieux atlas and showing significant β-γ normalized power difference across conditions. Extended Data Figure 3-2 shows the average normalized β-γ power for each significant region. F, The average normalized β-γ power at the L-MTG. One-way repeated measures ANOVA with Bonferroni post hoc test; **p < 0.01. Error bars represent mean ± SEM; n = 15. G, Condition-specific Spearman’s correlations between β-γ power and team flow index at L-MTG as a representative region. Positive correlation was found in the team flow condition (Spearman’s Rho = 0.56, p = 0.006), but not in the team only condition (Spearman’s Rho = −0.19, p = 0.43) or in the flow only condition (Spearman’s Rho = −0.02, p = 0.95). The lines indicate the regression lines. Shaded areas indicate a 95% confidence interval; n = 20.

Causality and II analyses during team flow. A, Causality analysis showing the top information senders among all RG-RG causal interactions. For each RG-RG connection, the line color matches the color of the RG name which sends the information. Notably, only in the team flow condition, L-MTC receives information from R-PFC and R-IFC. Extended Data Figures 4-1, 4-3, 4-4 show the method for grouping of ROIs. Extended Data Figure 4-2 shows detailed causality analysis. B, The mean normalized II value (Norm II) connectivity matrix for the brain regions (RG1–RG7). Normalized II is calculated by subtracting the mean per condition from the average II across conditions for each RG-RG connection across conditions. C, The mean global Norm II averaged across all RG-RG connections showing significantly higher interbrain (left panel) and intrabrain (right panel) mean during team flow condition. One-way repeated measures ANOVA with Bonferroni post hoc test; **p < 0.01. Error bars represent mean ± SEM; n = 15. D, RG-RG connections that shows significant (p < 0.05) Norm II in the team flow condition compared with other conditions. Three-way repeated measures ANOVA with Bonferroni post hoc test. Black lines indicate intrabrain and green line indicates interbrain RG-RG connections. D-L, dorsal-left.