If you have never witnessed the spectacle of someone speaking in tongues you won’t have to look far to find it. There is footage it in the satirical film Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan. And the internet serves up copious numbers of examples of people practising glossolalia, its technical term, on sites such as YouTube, in which believers ululate in a strange language, laughing or singing in religious ecstasy or, in one case, appearing to moo like a cow. The comments posted alongside them range from “amazing” to “and we thought the Muslims were insane”.

But millions of people are convinced that they speak in tongues — mysterious utterances of which they have no understanding — and that when they do so it is the Holy Spirit speaking through them. According to a Newsweek report nearly 20 per cent of American Christians speak in tongues several times a year and up to a third of churches encourage it.

In Britain this more exuberant brand of Christianity is growing fast in many charismatic evangelical churches — known as New Churches. The Church of England, while neither encouraging nor discouraging it, says: “The gift of speaking in tongues is recognised as a powerful expression of faith and spirituality.” Followers insist that it is a form of mental possession. Though they don’t understand what is coming out of their mouths they believe it is the spirit of God moving through them.

Well, now they may claim to have some scientific data to back them up. A study by neuroscientists at the University of Pennsylvania studied the brains of five people while they were speaking in tongues and found that they didn’t seem to be faking it.

The front and parietal lobes — the areas that manage control, a sense of orientation and language — showed decreased activity while they were speaking. To the layman that means that they were not willing or controlling their actions as people usually do when they talk.

All the volunteers had least a five-years history of speaking in tongues in church. Dr Andrew Newberg, associate professor in radiology at the university, made them start by singing a hymn and after a few minutes they began speaking in tongues. To measure brain activity each was given an injection of slightly radioactive material which enabled Dr Newberg and his team to take a freeze frame of the brain’ s blood flow.

He was surprised by the results. “The scans demonstrate that these subjects are not in control of the usual language centres,” he says. “That is consistent with their perception of a lack of intentional control while speaking in tongues. They can make themselves get into a state that allows this to happen, but once it begins they do not control any aspect of what is coming out.”

What does this prove? “It doesn’t prove that it is God, but it is something these people are perceiving in a real way,” says Dr Newberg, who is the author of Why We Believe What We Believe: Uncovering our Biological Need for Meaning, Spirituality and Truth. Donna Morgan, the co-author of the university study, is a born-again Christian and served as a research subject. She describes speaking in tongues thus:

“You’re aware of your surroundings, you’re not really out of control, but you have no control over what’s happening; you’re just flowing. You’re in a realm of peace and comfort and it’s a fantastic feeling.”

The findings are unlikely to cut much ice with sceptics of glossolalia who believe that it proves nothing more than people’s suggestibility and the power of belief. Dr Susan Blackmore, a British psychologist and specialist in consciousness, meditation and the paranormal, says it would be a “ludicrous jump in logic” to take this as proof that speaking in tongues is a divine experience.

“All this proves is that people speak in tongues,” she says. “It doesn’t prove anything about the claims those people make. It is an exact parallel with near-death experiences. Of course people have near-death experiences, but is it evidence of life after death? No. Of course people (who speak in tongues) aren’t faking it. There has been a release of frontal lobe inhibition; they have let off the normal control mechanisms that stop you talking gibberish. But that is all. Some people can slip into a trance quite easily. It’s very similar to hypnosis.”

Anyone who has seen a preacher speak in tongues will know that it can prove to be infectious. Once one person starts, more follow. No one wants to be left out.

Gerald Coates, the founder of Pioneer, a network of charismatic evangelical churches, says that the congregation at nearly all the New Churches in Britain now speak in tongues; in his youth he met a Pentecostal leader shortly after he found himself singing in an unrecognisable language. “As soon as he laid his hands on me it was like a river of words coming out,” he says.