Extended Data Fig. 2: Increased Within-group Neural Synchronization during Decision-making Phase relative to Waiting Phase.
From: Within-group synchronization in the prefrontal cortex associates with intergroup conflict
We compared within-group neural synchronization (GNS) during the group decision-making phase with that during the waiting screen of the intergroup contest game. a,b, We averaged GNS across the channels located in the rDLPFC and rTPJ respectively, and showed higher GNS during decision-making than waiting phases (a, rDLPFC: t85 = 5.823, p = 1.00 × 10−7, Cohen’s d = 0.628, 95% CI = 0.003, 0.006, b, rTPJ: t85 = 6.578, p = 3.70 × 10−9, Cohen’s d = 0.709, 95% CI = 0.004, 0.007), indicating increased GNS during group decision-making. Two-tailed paired samples t-tests, 86 six-person groups during decision-making and during waiting phases. c, To validate the Phase effect on the GNS, we generated within-condition pseudo groups for comparison purpose by randomly grouping 3 individuals from different original real groups under the same condition as a pseudo group, and treated Group (real vs. pseudo groups) as a between-subjects factor. d,e, We conducted ANOVAs on GNS with factors of Phase (decision-making vs. waiting) and Group (real vs. pseudo groups) in 86 six-person real groups and 86 six-person pseudo groups. We observed significant Phase-by-Group interactions on GNS in rDLPFC and rTPJ (d, rDLPFC: F1,170 = 10.161, p = 0.002, η2 = 0.056; e, rTPJ: F1,170 = 13.920, p = 2.60 × 10−4, η2 = 0.076). In addition, two-tailed paired t-tests on 86 six-person pseudo groups showed no significant difference between GNS during decision-making and waiting phases (d, rDLPFC: t85 = 1.400, p = 0.165, Cohen’s d = 0.151, 95% CI = −4.16 × 10−4, 0.002; e, rTPJ: t85 = 1.209, p = 0.230, Cohen’s d = 0.130, 95% CI = −0.001, 0.003). Data are plotted as boxplots for each condition in which horizontal lines indicate median values, boxes indicate 25/75% quartiles, and whiskers indicate the 2.5-97.5% percentile range. Data points outside the range are shown separately as circles. Solid lines start from the mean and reflect the intervals for the Mean ± S.E. **p < 0.01, ***p < 0.001, n.s. not significant. f, g, One-sided permutation test was used to verify the stronger decision-making-increased GNS in real than pseudo groups. Specifically, we calculated the mean difference between the two phases (GNSdecision-making – GNSwaiting) to indicate decision-making-increased GNS respectively for each real or pseudo group. We then compared the real-group sample with 1000 pseudo-group samples18,68,80. We tested the decision-making-increased GNS of the real sample against permutation samples based on decision-making-increased GNS (n = 1000, each permutation sample contains 172 within-condition 3-person pseudo groups). To test whether the effects observed in real groups was larger than that in pseudo groups, we reported the 1-sided p-values. The empirical p value was calculated as80: p = j/1000, j is the number of samples out of the 1000 permutation samples, of which the decision-making-increased GNS was larger than the observed value of real groups. We showed that, for both rDLPFC and rTPJ, the observed difference in decision-making-increased GNS in real groups were outside the upper limit of 95% CI of the permutation distribution. The one-sided p-values indicated specific decision-making-increased GNS in real groups rather than pseudo groups (f, rDLPFC: p = 0.004; g, rTPJ: p = 0.012).
