By Dimitris Xygalatas
What do peacocks and humans have in common? I suppose there may be other possible answers to this question, but one feature they do share is the use of extravagant, apparently senseless traits as a means of transmitting important information. When such transmission is beneficial to both senders and receivers, those traits will be favored by the forces of selection, even if at first glance they appear to be wasteful. In a nutshell, this is the core claim of costly signaling theory.
In the case of the peacock, the signal is built into its body. Its disproportionately long, iridescent tail is calorically expensive to produce, maintain, and carry around. It reduces agility, adds drag during flight, and makes its bearer a flashing target for predators. But as Darwin already noted, there is a method to this evolutionary madness. Although the tail itself may have no utility, the effort that goes into growing and maintaining it can still pay off. As only a fit peacock could afford to carry such a costly ornament and still be alive, peahens use this ornament as a reliable indicator of the male’s prowess. By selectively mating with males that carry extravagant tails, they are investing in good genes for their offspring, inadvertently pushing the males to grow ever more grandiose tails.
The same logic can also apply to behavioral traits. In humans, some of the best-known examples come from the domain of ritual. Signaling theories of ritual argue that costly ceremonies help solve important coordination problems: for any group that requires cooperation among its members, information on people’s levels of commitment is crucial. But declaring one’s loyalty to the group is cheap. Paying a hefty membership price provides more compelling evidence of commitment to the group and its values. Actions speak louder than words.
There is mounting evidence in support of this view. For instance, empirical research shows that people who participate in costly rituals are more committed to group causes. This is not lost on community members, who perceive participation as a signal of prosocial qualities. However, unlike the indexical nature of the peacock’s tail (what you see is what you get), human signals are embedded in complex sociocultural contexts.
For the sake of simplicity, formal models of signaling typically assume that the intensity of the signal varies while all else being equal. But in reality, all else is never equal. Social inequalities may influence default perceptions of a sender’s quality, impacting the signal’s cost-benefit ratio. While previous research treated this variation as noise, we designed a study to quantify it.
Our study, reported in Evolution and Human Behavior, took place in the island of Mauritius during the Thaipusam Kavadi, a Tamil Hindu festival held in honor of Lord Murugan. Performed by millions of Hindus in India and around thew world, it involves several days of activities that culminate with a pilgrimage to the god’s temple. Before embarking on the day-long procession under the scorching tropical sun, devotees have their bodies pierced with metal needles, hooks, and skewers. They also carry large portable shrines called kavadi. Those are built on a wooden, bamboo, or metal frame supported on the shoulders and are decorated with flowers and peacock feathers (in serendipitous but seemingly emblematic fashion, the peacock is Murugan’s symbol). The word kavadi, which in Tamil means “burden”, is what gives this ritual its name – aptly, as those structures can often weigh as much as a person.
In this setting, we recruited 80 adult participants of various ages. We measured the size of the kavadis they carried and the number of piercings they endured. After they completed their pilgrimage, we also asked them questions about their religious beliefs and practices and gave them a survey to assess their socioeconomic status.
We found great variation in both the intensity and form of signaling: the number of piercings ranged from zero to 600, and kavadis varied from petite to gargantuan. The festival provides different signaling opportunities and, as it turns out, participants harness them according to their means. High-status individuals carried larger and more flamboyant kavadis — for those at the top third of the socioeconomic ladder, almost three times larger than those at the bottom third.
Why would that be? Quite simply, because they could afford to. Building and decorating a kavadi can be expensive: the most elaborate structures can cost the equivalent of three months’ salary of an unskilled worker. And those larger kavadis are not necessarily heavier (at least not proportionally), as the affluent can purchase better and more lightweight materials (e.g. aluminum in place of iron), which allows them to amplify their signals even further.
“During the ritual, low-status individuals on average put almost four times more needles into their bodies compared to the upper classes. Lacking the material capital to compete with the elites, those of low status turned to whatever other means were available to them: quite literally, their own blood, sweat, and tears.”
On the other hand, there was a negative relationship between socioeconomic status and frequency of participation: across their lifespan, low status individuals carried the kavadi over four times more often. But it was not just a matter of frequency: during the ritual, low-status individuals on average put almost four times more needles into their bodies compared to the upper classes. Lacking the material capital to compete with the elites, those of low status turned to whatever other means were available to them: quite literally, their own blood, sweat, and tears.
It is worth noting that across all these metrics, there was a large effect of gender. While most women had only one piercing, the median number for men was 79. Men also participated in the ritual more times over their lifetime and carried kavadis that were on average over twice as large. Unsurprisingly, then, the associations with socioeconomic status were even stronger when we looked at the male-only portion of our sample.
While the physically demanding aspects of the festival are mostly a male affair, this does not mean that women do not engage in commitment signaling — far from it. For instance, they are more likely to fall into trance, which can be a hard-to-fake signal of devotion. Moreover, women play key roles in parts of the ritual that are seemingly peripheral but socially important nonetheless, such as hosting and organizing elaborate family feasts at the conclusion of the festival — a laborious and time-consuming activity.
Our study was the first to quantify the multi-layered costs of an extreme ritual and their variation along socioeconomic lines. Our findings are in support of a costly signaling view of ritual. Needless to say, cultural practices are complex and cannot be reduced to monocausal explanations. Our study has merely scratched the surface of one of the most widely performed rituals in the world.
Read the paper: Social inequality and signaling in a costly ritual