“…Early measurements of SMC, through the synchrony field, involved either intensive behavioral coding 26 or behavioral ratings 27 or explicitly manipulating study conditions to promote a narrow definition of synchrony, such as a dyad bouncing or swinging at the same time to a beat. 11,28 Mathematical applications to applied sciences now allow researchers to quantify SMC using both linear (cross-correlations) 5,22,[29][30][31] and nonlinear (i.e., coherence, relative phase, and cross-wavelet analyses) 1,2,6,32 approaches using a variety of different methods for capturing movement activity, including motion sensors, 9 accelerometers, 33,34 and musical instrument digital interface (MIDI)/audio recordings (e.g., to capture moments of contact during a drum hit). 15,35 SMC has also been measured through the timeseries analysis of movement obtained from the frame-difference method (FDM), 29,36,37 which measures the difference in luminance of grayscale pixels between consecutive video frames.…”