OVER the next few days, many Tamils will take part in an annual Hindu ceremony that involves amazing endurance. The keenest participants in the Thaipusam festival prepare with days of fasting, prayer and austere living. Then they have their skin pierced by sharp objects, which range from single needles to chunky skewers that pass through both cheeks. They trudge barefoot, or on shoes spiked with nails, to a temple dedicated to the god Murugan. Some carry elaborate bamboo canopies on their shoulders. Others drag chariots which are attached to the hooks that pass through their skin.

This may be an extreme case, but it is by no means the only instance where rites of communal and religious importance are seen as inseparable from pain or risk. During the Shia Muslim commemoration known as Ashura, which mourns the martyrdom of Hussein in the year 680AD, devout men emulate their hero’s fate by whipping themselves into a bloody mess with chains. And in Ireland, even as conventional forms of worship lose traction, there is no shortage of takers for austere Catholic rituals. For Saint Patrick’s Pilgrimage, worshippers converge on a small island for a three-day regime of minimal food and sleep, chilly barefoot walks, kneeling on stones and rigorous prayer. On the other side of Ireland’s divide, meanwhile, a good drummer in a Protestant marching band is expected to keep pounding till the blood pours from his fingers.

Dimitris Xygalatas, an assistant professor of anthropology at the University of Connecticut, is intrigued by communal activities that involve pain or the possibility of it. He has looked in detail at the Thaipusam festival as practised in Mauritius, and also at fire-walking rites in Greece and Spain.

One of the problems, he reports, is that participants are not good at describing what the ceremonies mean. They give answers like “this is what we’ve always done” or “without this, our community would not be the same”. In Greece, the expression “einai patroparadoto” (“it’s handed down from our fathers”) is considered sufficient explanation for a deep-rooted custom, such as the fire-walking practised in one village in honour of Saints Constantine and Helen on May 21st.

But as well as empathetic interviews, Mr Xygalatas’s research has drawn on more empirical techniques. During the fire-walk practised at mid-summer in one Spanish village, he and colleagues measured the heart-rates of the walkers who strode through a pit of charcoal, each carrying a loved-one on his back. Also monitored were the pulses of onlookers who were closely connected by blood or friendship with the walkers.

The results were striking. The walkers insisted that they had felt calm when performing the feat, during which steps have to be calibrated carefully to avoid horrible burns. But in fact, their heart-rates had soared, and more interestingly, people close to them in the audience experienced a surging pulse in precise tandem. In other words, the endurance of risk creates bonds not only among the risk-takers, but also among their nearest and dearest who are willing them on. In some ways, this confirms what any observer could see. The hugs exchanged by successful walkers with their family and friends spoke for themselves.

Mr Xygalatas used different methods to reach somewhat similar conclusions about the Thaipusam rite in Mauritius. Soon after the proceedings were over, people in the vicinity were interviewed, and then rewarded for their time with the equivalent of two days’ wages. A little later they were invited to hand over part of these earnings to charity. Generosity was greatest among people who had participated in the painful bits of the ceremony, and also among those who had followed the ceremony closely, albeit without being pierced. The experience of pain, whether directly or indirectly, seems to cement community bonds and increase the likelihood of “pro-social” behaviour.

Some might retort that the bonds created by common endurance of pain and risk are so obvious, and so deep-seated in human experience, that the point is really just a matter of common sense. Since the dawn of human consciousness, groups of people, mostly male, have been going out to hunt, fight or fish in stormy seas. A deep sense of commonality among those who experience those hazards was surely both a precondition and a consequence of these activities.

There is still a mystery as to why the collective endurance of pain and risk persists in our risk-averse age. Perhaps the absence of such extremes from everyday life increases their allure. But it is not obvious why such seemingly masochistic practices are considered, in ways that people cannot quite articulate, so vitally important to the identity of communities, be they cultural or religious. Is this just a hangover from a pre-modern, even a pre-agricultural, age?

Mr Xygalatas, who elaborates these ideas in many academic articles, in a Ted talk, and in a recent piece for Aeon journal, thinks not. Even now, new communities are being created by linking pain and pro-social feelings. As an example, he cites the ice-bucket challenge that went viral in 2014. People doused themselves with freezing water as a way of raising money to combat motor-neurone (Lou Gehrig’s) disease. In the words of Mr Xygalatas, it would not have been quite the same if participants had filmed themselves drinking cocoa.