Ritual fire-walkers’ heart rates sync with their watching loved ones, study finds

Fire-walkers’ heart rates and those of their watching friends and relatives fall into sync during ritual celebrations, according to a study published online Monday in the journal Proceedings of the National Academy of Sciences.

Studies have shown that synchronous social activities -- like dancing or playing music together -- enhance bonding and cooperation, and thus could be an important survival behavior. But is it the matching of dance steps or the sharing of certain emotions that helps build this rapport?

To study this, the international team of researchers needed to find people engaging in a group activity that did not involve them moving together. They found the perfect setup: a rural village in Spain named San Pedro Manrique, population 600. Each year on June 23, the summer solstice, people make a fire out of two tons of oak wood and, once the blaze dies down, a few will walk over the carpet of glowing coals (about 1,251 degrees Fahrenheit) as an audience watches.

They strapped heart rate monitors to 12 fire-walkers, nine spectators who were friends or relatives of at least one fire-walker, and 17 spectators who were not related at all.

The researchers found that while their actual heart rates didn’t match perfectly, the relatives’ or friends’ heart rates spiked and dropped in time with their fire-walking loved one. The non-related spectators’ hearts beat much slower and didn’t rise or fall at all in accordance with the rates of the fire-walkers’ hearts. Turns out that if you’re close to someone, you don’t need to do exactly what that person is doing to feel in sync with them during a ritual.

“This investigation opens a new dimension on the study of social relations and rituals, allowing the quantification of social effects in human physiology,” the authors write.

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