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THEORY-891: In dyads of untrained dancers facing each other, shared music and visual contact each raised interpersonal movement synchrony, with no interaction detected, in different movement components: lateral and hand movements synchronized through seeing the partner, anteroposterior movements such as head bobs through the shared music, and vertical bounce through both; which factor drove a component's synchrony was classified from its spatial direction and not from the periodicity of the synchrony

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Properties6
StatusActive
Version2
Tagscomplex-systems, embodied-cognition, social-science
SourceLIT-1424 — The geometry of interpersonal synchrony in human dance
Bears onQUESTION-063 — When a collective outcome such as synchrony, or the fall of a regulated quantity, can come from a shared external drive, from coupling among the members or from different internal routes, what measurement or intervention tells which architecture produced it, given that directional information measures under a recorded one-sided drive need not follow the coupling?
ReportsCASE-149 — Dancing to the same or different music, seen or unseen: in dyads facing each other, shared music and visual contact were removed independently, and each synchronized different movements of the pair

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Source

Bigand et al. (2024), LIT-1424, read in full in NOTE-1093 from PMC11266842 (CC BY), with Figure 2 and Document S1.

What was actually shown

  • Design. 70 participants in 35 dyads danced freely, facing each other, to 32 trials of eight rearranged songs. “we manipulated musical input (whether participants listened to the same or different music, presented through earphones) and visual contact (whether participants could see or not see each other) in a 2 × 2 factorial design.” The different-music trials paired songs 8.5% apart in tempo.
  • Measure. Whole-body motion capture decomposed by PCA into 15 principal movements (over 95% of variance); synchrony per movement as cross-wavelet power between the partners’ velocities.
  • Result. Four movements synchronized more with visual contact, five more with shared music, and bounce with both; “we found no evidence of an interaction between musical input and visual contact, and this was so for all PMs.” The spatial direction of the movements classified the three categories “with 100% accuracy”; their periodicity did not, and “confused 48% of the data associated with music-driven synchrony with partner-driven synchrony”. The authors: “when (unlike where) participants move does not reflect whether synchrony is established through music or partner vision.”
  • What could have come out otherwise. The same components might have synchronized under both factors, with the music’s effect absorbing the partner’s (an interaction); the categories might have shared a spatial signature; or the periodicity might have separated them. None did.

What this does not say

  • Not the direction of coupling. The synchrony measure is symmetric. That visual contact raises synchrony shows a coupling channel, not that the coupling is mutual rather than one partner following.
  • Not that the components are causally sealed off from each other. “Independent” here is the absence of a statistical interaction in this sample, not a demonstrated equivalence.
  • Not a general law of synchrony. One decomposition, one setting: untrained familiar pairs, 2.5 m apart, no touch, 40-second songs. The authors expect a side-by-side arrangement might reorganize the geometry, and give the visibility explanation as unproven.
  • Not that timing can never discriminate. The negative result is for the periodicity profile of synchrony; phase lags or directional measures were not tried.

Which part of QUESTION-063 it answers

QUESTION-063 asks, when a collective outcome such as synchrony can come from a shared external drive or from coupling among the members, what measurement tells which architecture produced it. Its “what would answer it” names two interventions and a statement of which tests can and cannot see the difference.

  • Answered in part, for one human case. Removing the shared drive and removing the coupling channel, each independently, separates the two architectures, and shows that both can operate at once in one pair, on different components. A timing-only measure of synchrony could not see the difference; a spatial decomposition could. That is a case of the question’s second requirement: a test (timing) that cannot see it, and one (component-wise intervention) that can.
  • Left open. The question’s other intervention, perturbing one member and measuring the others, is not done, so direction and peer-versus- hierarchy architecture (CLAIM-167, CLAIM-172) are not settled. Nor is a test for a shared drive that is unrecorded, which is what the question’s own limits on THEORY-275 point to: here the drive was the experimenter’s music, known and manipulable. And the second part of the question, telling one internal route to an outcome from another, is not touched.

The question stays Open. A Proposed THEORY cannot make it Answered (ADR-049).

Connections

  • CASE-149 documents the study as the record’s case, and bears on the proposed study CASE-045, which already takes the music’s beat as an exogenous input; this result says to expect the music and the partner to drive different components.
  • THEORY-129 is the shared-cue half in coral spawning, with coupling untested; this study tests both halves in one system.
  • THEORY-275: there, a directional measure follows a recorded drive and misreports symmetric coupling. Here, a timing measure cannot apportion synchrony between drive and coupling. Both are cases of an observational test failing where an intervention succeeds.

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