Synchronized arousal between performers and related spectators in a fire-walking ritual
- aCenter of Functionally Integrative Neuroscience, Aarhus University, 8000 Aarhus, Denmark;
- bInstitute of Anthropology, Archaeology and Linguistics, Aarhus University, 8000 Aarhus, Denmark;
- cFaculty of Humanities and Social Sciences, Victoria University, Wellington 6140, New Zealand; and
- dCenter for Cognition, Action and Perception, University of Cincinnati, Cincinnati, OH 45221
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Edited* by Riitta Hari, Aalto University School of Science and Technology, Espoo, Finland, and approved March 28, 2011 (received for review December 14, 2010)

Abstract
Collective rituals are present in all known societies, but their function is a matter of long-standing debates. Field observations suggest that they may enhance social cohesion and that their effects are not limited to those actively performing but affect the audience as well. Here we show physiological effects of synchronized arousal in a Spanish fire-walking ritual, between active participants and related spectators, but not participants and other members of the audience. We assessed arousal by heart rate dynamics and applied nonlinear mathematical analysis to heart rate data obtained from 38 participants. We compared synchronized arousal between fire-walkers and spectators. For this comparison, we used recurrence quantification analysis on individual data and cross-recurrence quantification analysis on pairs of participants' data. These methods identified fine-grained commonalities of arousal during the 30-min ritual between fire-walkers and related spectators but not unrelated spectators. This indicates that the mediating mechanism may be informational, because participants and related observers had very different bodily behavior. This study demonstrates that a collective ritual may evoke synchronized arousal over time between active participants and bystanders. It links field observations to a physiological basis and offers a unique approach for the quantification of social effects on human physiology during real-world interactions.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: ivana.konvalinka{at}gmail.com.
Author contributions: I.K., D.X., J.B., U.S., E.-M.J., and A.R. designed research; I.K., D.X., J.B., U.S., and E.-M.J. performed research; S.W. and G.V.O. contributed new reagents/analytic tools; I.K., D.X., J.B., G.V.O., and A.R. contributed conceptual framework; I.K. analyzed data; and I.K. and D.X. wrote the paper.
The authors declare no conflict of interest.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1016955108/-/DCSupplemental.