AIDA – Attention, Interest, Desire, Action – is a very old concept in the ad industry, but it still lies at the heart of most copywriting. The idea is that, to be successful, an ad must have a structure like this:

Attention – the copywriter’s way of attracting the reader’s notice, and, often, of selecting the correct readers. Grabbing attention is usually the job of an ad’s headline. A headline that reads

Do women like bald guys?

grabs our attention by making us think. It also selects the audience – guys with thinning hair are going to be much more interested in reading the rest of the ad than guys with long, blonde locks.

Interest – a development of the attention-grabbing headline, developing the idea and encouraging us to read on, often by presenting information that backs up the idea presented in the headline. This phase is usually located in the bodycopy of an ad:

Surveys have found that 92% of women prefer guys to have a full head of hair. Until now, bald men have been fighting against the odds in the battle of the sexes!

If you’re a baldie, you’re both interested and a little horrified by that statistic (which I’ve made up, by the way, because everyone knows that a nice smooth scalp is what the girls really like). But wait – what’s this? The copywriter is drawing us in deeper with ‘until now’….

Desire – presents a solution to the problem, or a delivery on the promise, that’s been presented in the ‘attention’ section (the headline) and developed in the ‘interest’ section. This section contains the key benefit of the product:

New Eze-Lox Spray-On Hair offers you the chance to release the sexiness and charm that lies within. At just $1899.99 for a 50ml tin, can you afford not to use it?

Action – finally, this section (sometimes called the ‘call to action’) makes the sale. It should re-stress the key benefit of the product and tell readers how to buy:

Call 0800-572-387 today to order your free sample. Let Eze-Lox turn you into a tiger!

Even ads that consist of not much more than a headline, an image and some contact details can usually be broken down into a four-part AIDA structure. The majority of advertising still sticks to it, even if the sequence is heavily compressed. Most copywriters apply the formula unconsciously. Think about Adwords ads:

Losing your hair?
Let Eze-Lox Make you
A Babe Magnet! Just $1899.99/50ml
www.eze-lox.com

The ‘attention’ and ‘action’ phases are very clear: they’re located in the headline and the clickable URL respectively. ‘Interest’ and ‘desire’ are bound up in the middle two lines. It’s not clear which bit arouses interest and which stimulates desire, or whether you can distinguish the two phases from one another. But they’re both there. If you’re the kind of guy who’s interested in this product, ‘let Eze-Lox make you a babe magnet! Just $1899.99/50ml’ should really speak to you. The copywriter is exploiting one of your key motivations.

UPDATE : Stoney’s just written a great post over at Searchengineland that offers a very thorough analysis of this subject, using slightly different terminology. Worth a read!