This is somewhat a response to this week's post by Laurence Minsky, and somewhat a rant. Apologies on both accounts.
I've always had a belief on this that advertising is not intended to make you purchase something. It is intended to make it acceptable for you to purchase something. Either by changing your own perception, or by changing the perceptions of your peer group.
This is why there's problems when market researchers ask if an ad makes a consumer more or less likely to buy a product. Because the answer is no. It won't. Unless the commercial/ad gives new information about the product that changes the consumers actual knowledge of what the hell the product does, it won't make them more likely to buy it. It CAN however make it more ACCEPTABLE for them to buy it, which is what leads to sales in the end.
Ads don't happen in the vacuum of a focus group, they happen in a real world where others react. If one person hates a commercial for Nike, but all their friends loved it, the person's opinion doesn't matter when it comes to their likelihood of buying Nike shoes. It has become acceptable in the peer group in spite of them.