Synchronised arousal between performers and related spectators in a fire-walking ritual
(2011)
Konvalinka, I., Xygalatas, D., Bulbulia, J., Schjoedt, U., Jegindo, E., Wallot, S., Van Orden, G., Roepstorff, A.
Proceedings of the National Academy of Sciences PNAS, Vol. 108, No. 20, 8514-8519pp.

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Collective rituals are present in all known societies but their functions are matters of long-standing debates. This ambitious and technically demanding study produced the first *quantified* demonstration from a natural human ecology that an extreme collective ritual coordinates the arousal of participants and spectators. We found that during a Spanish firewalk, the heart rhythms of spectators became aligned to known firewalkers. Intriguingly, spectators who were related to at least one fire-walker exhibited shared patterns of arousal to unknown fire-walkers. This suggests that an extreme ritual may extend the boundary of empathetic concern from related to unrelated performers. Quantifying a ritual reveals unnoticed subtleties.

The article received global attention, for example:
http://www.nytimes.com/2011/05/03/science/03firewalker.html

http://news.nationalgeographic.com/news/2011/05/110504-fire-walking-hearts- beat-science-health-heartbeats/