Now, Dr Robert Heath, an advertising specialist from Bath's School of Management, has managed to lift the veil another inch or two. His theory, which is only a little counter-intuitive, is that it is emotion, rather than rational data, that works best, at least for enhancing brands.
Heath cites the success of the 'Papa/Nicole' Renault Clio ads, which centred on philandering French characters. 'The launch of the Renault Clio was an outstanding success, despite the ad failing to communicate the main message of small-car convenience and big-car luxury,' he explains.
Slightly more weakly, the adman and academic suggests that it was 'some aspect' of the emotional appeal that was at work, and that perhaps it was the evocation of positive emotions that lowered attention to more rational matters in the minds of consumers.
Anyway, Heath's case is that in a study of the effect of 23 TV ads in the US and 20 in the UK, consumers who had been exposed to executions with high emotional content showed a marked positive shift toward the brand involved. Those who had seen ads with low emotional content, even when the work contained lots of news and information, showed no real shift.
The message for TV advertising is clear: creativity and well-told stories enhance the images of brands and presumably lead to success over time. The research would seem to back the belief in the industry that advertising is often there 'just to allow the brand to set up a dialogue with the consumer'.
So far, so good. But does such research have any wider implications about the ideal media mix to use?
The most obvious point is that if it is true that ads with high emotional content transmit positive brand vibes, then TV is the best place for that interaction.
In such a context, it is perhaps worth asking whether it is entirely rational for UK advertisers to be turning their backs on conventional TV as they are. Have you ever seen anybody getting emotional about, or emotionally involved in, an iTV ad for the Clio?
One can get excited about online price comparisons for the vehicle. But what was it that drove you in the direction of that model in the first place, as opposed to another provider of small-car convenience with big-car luxury?
The Heath research co-incided with the latest data on TV and interactive ads in the UK and US. According to Universal McCann, TV advertising in the US has held up very well in the face of electronic rivals and will take about $72.5bn (£37.2bn) this year - about a quarter of all spend. The really interesting thing is that this has held constant as a proportion since 2000. Is this because US admen are dozy and simply don't understand this interactive malarkey? It's possible, but I doubt it.
At the same time ZenithOptimedia estimated that online advertising in the UK accounted for 13.5% of spend and would rise to 20% by 2009. This is the highest percentage in the world, and double the rate in the US; Sweden and Norway are the only other nations spending more than 10% online.
This could be because of high broadband penetration here and because the industry is twice as smart and technologically adroit as the Yanks. Or it could just mean things are starting to get out of kilter. Certainly the implications are worth getting emotional about.
30 SECONDS ON ... RENAULT CLIO 'PAPA/NICOLE' ADS
- The first Renault Clio ad, featuring Nicole (Estelle Skornik) and Papa (Max Douchin), was broadcast on British TV screens on 1 April 1991.
- The series ended in 1998, when Renault and its ad agency, Publicis, chose to conclude the story with Nicole's wedding, at which she chose Bob Mortimer over Vic Reeves.
- This final ad, which cost £1m, was shown on 29 May at 7.40pm on ITV, during Coronation Street.
- In the seven years that the ad campaign ran, 300,000 Renault Clios were sold in the UK, with consecutive year-on-year sales rises to the end of 1997.
- The campaign was the most successful on record, with a 93% recall figure, according to a Sofres Automotive study into car advertising. In 1996 another survey found that Nicole was recognised by more Britons than John Major, Bob Hoskins or Chris Evans.