Between‐brain coupling as a behavioral predictor
FM
To examine the predictive value of between‐brain coupling on behavior, we constructed three LME models, each consisting of Condition, ROI, and the continuous value of WTC as fixed factors and dyad IDs as a random factor, for prediction of unlagged motion synchrony (“Total Sync”). The models differed in the level of interaction between the three fixed effects, such that the first model included only the main effects of the fixed factors, the second model additionally included all 2‐way interactions between the fixed factors, and the third model included main effects and all possible interactions between the fixed factors. A Type II Wald Prediction of Total Sync by WTC in each Condition in each ROI pairing.Numeric values and significance of WTC slopes as predictors of Perfect Sync values in the FM and IS Conditions in each ROI.Est. = 0.22S.E. = 0.07

Est. = 0.17S.E. = 0.06

Est. = 0.03S.E. = 0.03
n.s.Est. = 0.01S.E. = 0.04
n.s.Est. = 0.07S.E. = 0.04

Est. = 0.04S.E. = 0.02

Est. = −0.1S.E. = 0.04

Est. = 0.03S.E. = 0.05
n.s.Est. = 0.04S.E. = 0.02

Est. = 0.24S.E. = 0.04

Est. = 0.03S.E. = 0.4
n.s.Est. = 0S.E. = 0.02
n.s.Est. = 0.11S.E. = 0.03

Est. = 0.03S.E. = 0.03
n.s.Est. = 0S.E. = 0.01
n.s.Est. = 0.17S.E. = 0.04

Est. = −0.05S.E. = 0.05
n.s.Est. = −0.01S.E. = 0.02
n.s.