A new advertising campaign is unlikely to convert the non-believer, writes Dr Paul Harrison, a senior lecturer in consumer behaviour and advertising at the Deakin Business School.

News that Christian churches in Australia are about to start an advertising blitz to persuade people to bring Jesus into their lives, once again shows how naive and uninformed businesses, government, and people are generally when they believe that advertising has some magical power to persuade people to behave the way they want them to.

It seems that thousands of churches across 15 Christian denominations in NSW are behind a project that aims to promote the message that the teachings of Jesus are still relevant. The campaign, based around the slogan, "Jesus. All About Life" begins in three weeks. Unfortunately, those with faith have probably placed too much of it in the ability of an advertising campaign to convert non-believers, and even lapsed Christians.

Yes, advertising does have some influence over attitudes and behaviour, but the reality is that it can only really work as a "nudging" tool. In other words, an advertisement will incrementally move you toward a decision, but there are a whole bunch of other variables that will determine your final behaviour or decision. In reality, one-way advertising is a relatively weak motivator when it comes to consumer behaviour (although the ad agencies wouldn't tell you that when you are about to give them $1 million).

It's quite a romantic notion to think that advertising is powerful. It is a myth partly propagated by the advertising industry, and partly supported by our experience as consumers. We see a lot of ads, we know that businesses spend millions on it, so it must work... mustn't it? We see hundreds, even thousands of advertisements every day, but when you think about it, what do we do? Mostly nothing in response.

Advertising works best amongst people who are predisposed to notice your ads. In other words, it is your loyal customers and current users who are most likely to notice your advertising, followed by people who have been primed to notice them.

For example, when are you most likely to notice advertisements for companies that sell car tyres?

When you have a flat tyre or need to replace your tyres, of course. You are primed to notice these advertisements, because you are cognitively predisposed to seek out information about that particular attitude object.

Who is most likely to notice, and be persuaded by a Christian advertisement, then?

The people who commissioned the advertising campaign; current, faithful, committed Christians, and maybe people who were already willing to be persuaded. It's a simple proposition, but one that is often not stated - advertising works best amongst current users. It makes current users (who are satisfied with the product) feel good about themselves, and it has the potential to increase loyalty toward the product, but only amongst current users. So an expensive ad campaign is not going to do the trick.

Advertising is most affective when combined with a complete and thorough marketing mix, i.e., a product people "want", a product that is easy to access, and something that requires little cost (including factors such as effort, and social and psychological risk).

If you ask me, I think the thousands of churches spending so much money on an advertising campaign like this are not really getting good value. They would be better off spending the money understanding why people are turning away from them, and then examining whether the church is able to respond to this.

But maybe I don't have enough faith.

Dr Paul Harrison is senior lecturer in consumer behaviour and advertising at the Deakin Business School.