I'm going to dispute this based on things told to me by a friend who works in advertising. Their whole goal and struggle is to sell the ad to the people who want their product advertised. Whether or not the ad works on the general public is, in the end, completely immaterial. The challenge is to make the ad agency client think it's going to work.
The client comes to the ad agency with a long laundry list of things they want emphasized about their product, and a vague but simultaneously strong sense of how they want it presented. The client is, for obvious reasons, exceptionally attached to a preconceived image of their product which they want the ad agency to purvey, or at least, not undercut. So, what follows is a long, usually cordial (but not always), arm wrestle between the client and the agency, during which the agency tries to pry the client away from their preconceptions and open them up to novel ideas the agency authentically thinks will work. Clients differ in their degree of stubbornness, and the ad agency has, always, to tread lightly in how much they push them, least they just take their business elsewhere. (Ad agencies refer to stubborn clients as "untalented," and to pushover clients as "talented," in exactly the same way hypnotists use that term. A "talented" subject for a hypnotist is the one most easily hypnotized, the one who comes to the hypnotist already believing in his mesmerizing powers, and drops into a trance at the slightest suggestion. Ad agencies love "talented" clients, but they are the exception rather than the rule.) So, the client always wins, and in most cases the ads you see are not the ads the ad agency wanted to make, but some bastard hybrid of conflicting value systems. For that reason, ad ends up being completely unpersuasive, and often irritating, such that you have to wonder if there's anyone in existence who taken in by it.
The ad agency takes comfort in the fact that almost any ad works for the basic reason that it alerts the consumer to the existence of the product such that they add it to their list of possible choices when buying that type of product. An extensive ad campaign makes the consumer say," This product must be O.K. since they make enough money to pay for this extensive ad campaign. Anonymous Laundry Detergent must have something wrong with it: they can't afford TV commercials." That is the power of advertising: the product that can afford extensive ads must be an O.K. product: if people weren't buying it, how could they afford those ads?
So, yes, ads work, but the notion that ad men are master psychologists who are subliminally manipulating the stupid masses at levels they'll never understand, is a lot of hooey. Ad agencies rarely get the chance to pull out all their creative stops, and when they do, it's as hit or miss as any gamble.