WTF

That sounds like misinterpretation of studies if I had to guess. If anything maybe it would be how well they work at certain investment levels with breakpoints where it is no longer worth putting in additional money, or the efficacy of CERTAIN types of advertising. But IF they work at all? I am highly suspect of that even being a question. Brands that are well advertised are well known, and people who aren't bothered to do research into every single product they buy are more likely to buy a product they have heard of before.

And if you're an independent creative, like author, artist, musician, developer, and you DON'T advertise, you will sell zero copies of your work.