Synchronized behavior increases assessments of the formidability and cohesion of coalitions

Synchronized behavior is a common feature of martial drills and military parades in many societies. Hagen and colleagues (Hagen & Bryant, 2003; Hagen & Hammerstein, 2009) hypothesized that the intentional enactment of synchronized behavior evolved as a means of signaling coalitional strength, as individuals who can synchronize are able to act in concert in agonistic contexts. Previous research has explored either the subjective consequences of synchrony for participants in synchronized behaviors or the effect of synchrony on observers' impressions of rapport among the synchronized actors. Critically, left untested is the central tenet that, by communicating that the individuals constitute a coordinated unit, synchronized behaviors signal elevated fighting capacity. We tested this prediction in two studies by asking large U.S. samples to judge the envisioned physical formidability - previously demonstrated to summarize assessments of diverse determinants of fighting capacity - of U.S. soldiers or terrorists on the basis of audio tracks of either synchronous or asynchronous footsteps. Consonant with the agonistic signaling hypothesis, participants judged the synchronized target individuals to be larger and more muscular than the unsynchronized individuals, an effect mediated by their assessment that the former collectively constitute a single unified entity. Although synchronized footsteps also enhanced listeners' perceptions of social bonding among the target individuals, this assessment did not mediate their judgments of elevated formidability, suggesting that synchrony primarily signals fighting capacity via revealed entitativity rather than inferred motivation.