Dec. 27, 2009  -- You may not be Christian, or religious, but if you live in almost any developed country, you will find it hard to get away from Christmas rituals at this time of year. Of course, many of them are secular: where would the holidays be without rampant consumerism, drunken partying, over-indulgence and family feuds? Then there are the rituals whose religious origins have all but faded, such as Santa Claus.

But while Christmas rituals can be exciting for children, they certainly don't have any of the high drama of those practiced by other faiths.

Take the Australian Aboriginal religious initiation rites that includes scalp biting, fingernail extraction and cutting the initiate's penis with a stone knife, without which a man is not considered spiritually mature.

Or the extremes of the sacred fire dances performed in New Guinea, where in order to commune with their ancestors men enter a trance state wearing masks decorated with blood drawn agonisingly from their own tongues.

By contrast, the most extreme ritual a Christian is likely to engage in is being dunked during baptism. Why do some religions have rituals that are so much more traumatic than others?

This question has been exercising University of Oxford anthropologist Harvey Whitehouse for over two decades. He is not the first to note that religions tend to fall into two distinct types -- those based on extensive teachings, such as Christianity and Islam, and those based on iconography and personal interpretations, including most small-scale religions and cults. Whitehouse's particular take, though, is to suggest that rituals themselves generate this dichotomy.

In recent years, several researchers have developed the idea that religion taps into intuitive ways of thinking. Even as young children we seem predisposed to believe in the supernatural, which probably explains why we develop beliefs in spirits, an afterlife and gods as we get older.

This appears to explain many of the shared characteristics of religions across the globe. But it cannot be the whole story, says Whitehouse, because it also describes beliefs in non-religious supernatural beings, such as the tooth fairy and Father Christmas. So what distinguishes the fairies from the gods?

Whitehouse points out that even when religions are founded on intuitive ideas, acquiring religious knowledge often comes at a cost, and it is this difficult-to-acquire knowledge that is most highly valued. Indeed, it is the complex concepts that are hard to acquire and understand that give any religion its unique identity. This, he believes, is what distinguishes religions from other beliefs, such as superstition. And this is where the rituals come in, he argues. It helps the religious grasp the hard ideas underlying the religion.

It is not clear whether willingness to indulge in ritual is an inherited trait. Whitehouse suspects it is, and is planning studies with children to find out. Clearly, though, ritual is not the exclusive preserve of religion. Obsessive hand-washing, drinking tea in a certain way and crossing oneself with holy water all have one thing in common: "Rituals are by their very nature puzzling activities that invite interpretation," says Whitehouse. Rituals also have an emotional aspect - ranging from a comforting feeling of security or togetherness to extreme terror. And rituals can be repetitive - although the frequency of repetition varies enormously. These three traits are what make religion and ritual such good bedfellows. They provide the all-important elements that allow a religion to flourish: meaning, motivation and memory.

A complex web of interactions link rituals to religion, but for Whitehouse, any attempt to tease out a thread must start with memory. "The reason why there are only two types of religion is that there are only two basic systems of memory that matter," he argues. The first is semantic memory, which deals with things we are conscious of remembering and stores what we have learned about the world. Then there is episodic memory, which hangs onto memorable events from our own lives. Whitehouse argues that to persist and spread, a religion must elicit the help of rituals that reinforce memories in both these systems.

Consider some of the most extreme rituals. According to Whitehouse, they are all classic examples of rituals that invoke episodic memory -- creating personally significant events that are imprinted into the initiate's mind. They are characteristically infrequent, often once-in-a-lifetime experiences, and all are highly traumatic. Being personally consequential and shocking, they are likely to evoke intensely vivid memories, known as "flashbulb memory" of the kind experienced by people with post-traumatic stress disorder. They also leave participants struggling to make sense of the experience, and so constructing elaborate personal meanings for what has happened. Such low-frequency, high-arousal rituals are the lifeblood of "imagistic" religions -- cults and other religions based on iconography, analogy and intense cohesion.

The second type of ritual is exemplified by Muslim prayer, called salat. Muslims pray at least five times a day, following a highly prescribed routine that includes facing Mecca, bowing to Allah and reciting extracts of the Koran. Like Catholic mass and the Jewish Sabbath observance, salat is a high-frequency, low-arousal ritual - the sort characteristic of doctrinal religions. Repetition fixes the information in semantic memory so that believers acquire a deep knowledge of their particular religion's liturgy, no matter how complex or counterintuitive. This way of doing things has advantages over the imagistic mode in that it keeps the ideas at the core of a particular religion cohesive and stable. As a result, doctrinal religions spread easily - so all the world's major religions fit this pattern. By contrast, imagistic religions, with their more creative, fluid and idiosyncratic rituals, tend to be small-scale and localized.

So how come doctrinal religions haven't overrun imagistic ones? Religions driven by frequent, unexciting rituals face their own problems, Whitehouse says. The most crushing of these is what he has dubbed the "tedium effect". An obvious solution would be to make the rituals more emotional, but he says this risks inspiring participants to generate personal interpretations and so fracturing the religion. They would undermine the doctrinal orthodoxy that is crucial for these sorts of religions to flourish. One strategy is to employ charismatic preachers to offset the tedium and use more committed members of the religion to police it and keep the flock in check, which might explain the hierarchical nature of organized religion.

Whitehouse's theory is compelling because it integrates many aspects of religion, from the psychological to the socio-political, but how reliable is it? One advantage is that it makes testable predictions. For example, religious rituals are unlikely to be both low frequency and low arousal - because such rituals would not be easily remembered - or high frequency, high arousal - because most people will not willingly undergo too much torment even in the name of religion. It also predicts that doctrinal religions will tend not to have low-frequency, high-arousal rituals because they undermine orthodoxy, and imagistic religions will tend not to have high-frequency, low-arousal rituals because these undermine exclusivity.

Whitehouse and his colleagues are currently compiling the world's largest database of religious rituals to test such predictions. It is part of an ongoing project, EXREL (Explaining Religion), but preliminary indications suggest that religious rituals do indeed cluster around two forms that associate respectively with the two types of religion. He describes the observed pattern as "bunching with some outliers", and points out that you would expect the occasional anomaly because there is nothing stopping the emergence of an exciting, high-frequency ritual or a boring, low-frequency one. However, he expects to find that such rituals are a flash in the pan because they don't have what it takes to glue together compelling religion.

Not everyone is convinced by Whitehouse's argument. Robin Dunbar, also at the University of Oxford, says it fails to address the key question of why we have religion at all. He believes religion evolved as a survival mechanism and that the main purpose of rituals is social cohesion, which is at the core of our success as a species. And Whitehouse's theory doesn't explain why even within major religions there are pockets of extreme behaviour, such as the self-flagellation rituals practiced by some Shia muslims during the holy day of Ashura, the practice of anaesthetic-free infant circumcision in conservative Jewish circles, or the re-enactments of crucifixion by some Christians in the Phillipines.

Christmas itself is probably a little too racy to fit neatly into Whitehouse's theory. But Whitehouse has an explanation. Feel-good, annual events tend to be a feature of doctrinal religions, he says. Happy or euphoric experiences are not remembered in the way traumatic ones are, so you can have the occasional knees-up to boost motivation without undermining doctrine. "You just need to find the sweet spot," he says. Which at this time of year is probably good advice for anyone of any religious persuasion, or indeed none at all.