Fire-Walkers and Their Friends Had Matching Heart Rates. Strangers Did Not.
Konvalinka et al. (PNAS, 2011): at a Spanish fire-walk, 38 people wore heart monitors; walkers synced with related spectators, not strangers. Friend ideas.
In this article9 sections
On the night of 23 June, around midnight, the rural village of San Pedro Manrique, in Spain, holds its annual fire-walk. A research team put chest-strap heart monitors on 38 people at one of these nights: 12 who walked, 9 who were standing in the crowd because someone they knew was walking, and 17 who had no tie to anyone on the fire. Each walk lasted 4 to 5 seconds. Over the 30-minute ritual, the heart-rate traces of the walkers and the people who knew them rose and fell in step. The strangers’ traces did not.
That finding comes from Ivana Konvalinka, Dimitris Xygalatas and six co-authors, in a paper titled “Synchronized arousal between performers and related spectators in a fire-walking ritual,” published in the Proceedings of the National Academy of Sciences in 2011. It is a small study with a large idea attached.
What did Konvalinka and colleagues measure at the fire-walk?
The team recorded heart rate with Polar chest-strap transmitters, averaged over 5-second intervals, across a 30-minute ritual, and compared it with a 30-minute baseline taken beforehand. I read the full text on PubMed Central, where the authors describe the participants as 12 fire-walkers, 9 related spectators and 17 unrelated spectators. Related meant relatives or self-reported friends of at least one walker. Unrelated spectators were recruited at random hours before the event.
The analysis used recurrence quantification, a nonlinear method, on each person’s data, and cross-recurrence quantification on pairs of people. The abstract’s result: fine-grained commonalities of arousal between walkers and related spectators, but not unrelated ones. Because walkers and spectators behaved very differently with their bodies, the authors suggest the link may be informational: knowing the person on the fire seems to be what tuned the spectator to the event.
Is this the collective effervescence Durkheim described?
The authors frame it that way. They cite Émile Durkheim’s idea of collective effervescence, from The Elementary Forms of the Religious Life, first published in French in 1912. In the 1915 English translation by Joseph Ward Swain, which is on Project Gutenberg, Durkheim writes of gatherings: “The very fact of the concentration acts as an exceptionally powerful stimulant.” Konvalinka’s team offered a way to put a number on that, and the number only showed up for the connected people.
What does the study not show?
A lot. It is one village, one night, 38 people, and only 9 in the group that carries the main result. Nobody randomly assigned who was related to whom. The authors list their own limits, including that age, sex and body mass could affect heart rhythm, that the data were too coarse for breathing effects, and that anticipation of the ritual may explain some similarity already seen at baseline. They also did not measure friendship, trust or anything afterward. Synchronized arousal is a statement about hearts during an event, not about what a friendship looks like next month.
Two nearby papers fill in a little. Fischer and colleagues (PLoS One, 2014) studied a fire-walk in a Mauritian Hindu community and found that walkers had the biggest heart-rate rise and reported more happiness afterward, while low-ordeal participants with family ties to walkers reported more fatigue. Xygalatas and colleagues (Psychological Science, 2013) looked at rituals of varying severity with economic measures of generosity, though I only retrieved the opening of that abstract and am not reporting its results.
What should you do with your friends, then?
The reading is narrow: people who care about someone seemed to share that person’s arousal while the person did something intense. The author’s inference, not the study’s, is that a friendship may get more out of a night with some stakes than out of a third dinner at the same restaurant. This is consistent with Jeffrey Hall’s estimate of the hours that friendship takes, because it suggests some hours do more than others, though Hall’s work did not test fire.
Here is a hype-level menu. None of these were tested in the studies above; they are things that share the features the fire-walk had, which are real stakes, a start and an end, and someone you know in the middle of it.
| Activity | Why it fits the pattern | Cost |
|---|---|---|
| Enter a race or a charity swim together | A fixed date, visible effort, friends on the sidelines | Training weeks |
| Do something that makes you nervous in front of friends (open mic, a first climb) | A real chance of failing, with people who know you watching | One evening |
| Cook a hard recipe against a deadline for guests | Shared effort toward a result | A weekend afternoon |
| Take a night hike or a trip with a hard first leg | Mild stakes, a story afterward | A day |
| Show up for a friend’s big moment (a recital, a talk, a marathon finish) | The spectator role in the study | An hour or two |
Note the last row. The spectators tied to walkers were not passive; they were tuned in, and per the 2014 paper that came with a fatigue cost. If you are the one trying something hard, pick friends who will come and watch.
For the calendar side, adult friendship runs on invitations that name a date, and a race with a registration deadline is an invitation with a built-in date. For a gentler version, seven attention-sharing activities from a different study sit at the low-stakes end of the same scale. At the heavy end, a sibling post on post-traumatic growth covers what happens when the stakes are not chosen.
One practical wrinkle: the best of these activities start early, and a plan with friends can die at 6 a.m. on the day. DontSnooze gives you 30 seconds after the alarm to record a video showing you are up, and if you do not, a random photo from your camera roll goes to friends you chose. That is the author’s inference, not a finding from any of these studies: a deadline friends can see is one more reason to be at the start line.
Questions people ask about heart-rate sync and ritual
Does heart-rate synchrony prove two people are bonded?
No. Konvalinka and colleagues measured heart-rate patterns, not closeness, trust or liking, so the 2011 paper cannot say that synchrony creates friendship. Arousal over 30 minutes tracked more closely between walkers and people tied to them than between walkers and strangers in the same crowd.
Did the 2011 fire-walking study test whether rituals make people closer?
Not directly. The PNAS paper tested whether arousal over time was synchronized, using heart-rate data from 38 people. Xygalatas and colleagues (Psychological Science, 2013) looked at rituals of different severity with economic measures of generosity, which is closer to a test of prosocial effects, but neither study measured a friendship afterward.
Do you need a fire-walk or something painful to get the effect?
Nothing in these studies says so. The 2011 paper recorded one existing ritual with no comparison activity such as a concert or a hike. Fischer and colleagues (PLoS One, 2014) found the highest-ordeal participants reported more happiness afterward, while close relatives of walkers reported more fatigue.
Why did the study only count related spectators?
The authors wanted to separate being present from being connected. Related spectators were relatives or self-reported friends of at least one walker; unrelated ones had no tie to anyone in the ritual. Only 9 of the 38 recorded people were in the related group.
The next small action costs nothing: pick one friend and one dated, slightly scary thing, and send the invitation today.