Why it is a question
THEORY-891 reports Bigand et al. (LIT-1424, read in NOTE-1093): in 35 dyads, shared music and visual contact each raised synchrony in different movement components, with no interaction detected, and the components’ spatial direction, not the periodicity of their synchrony, classified which factor drove them. No interaction was bounded, one decomposition was used, and one temporal representation was tried. It sharpens part of QUESTION-063: whether removing drive and channel separately keeps discriminating, and whether every timing measure fails.
What would answer it
An independent replication with the same 2 × 2 logic (shared music removed, visual contact removed, each independently) in a new sample, or the public data (IIT Dataverse, doi:10.48557/UR2GBG) reanalysed under a different movement decomposition, showing that the music-driven and partner-driven components stay distinct, that an equivalence test bounds their interaction near zero, and that a periodicity measure still fails to classify them while a spatial one succeeds. Independence fails if a powered test finds an interaction; the timing result fails if another temporal representation (phase lags, directional measures) does tell the two kinds apart. Neither says anything about the direction of the partner-driven coupling.