When I was 19 or so I dated a guy for a short while that was a very good artist. He was also a marketing major working on his thesis about subliminal advertising and tricks of the trade. Although his paper was all about Playboy Magazine, he also had lots of other stuff to show me. The Playboy stuff was fascinating - there was a lot involved and it would take me showing you old Playboys to explain it all. This was probably 1980 or so, and I haven't seen a Playboy in years, so I don't know if they still use those old tricks.
I still look at ads with a keen eye. The picture above is the new Louis Vuitton ad. The artists have totally reproduced the female anatomy in the crotch of her pants. I was amazed when I saw it and am surprised no one online has mentioned it. Maybe because it's supposed to be subliminal. Maybe everyone else is looking at her eyes. But if you look there, it's pretty obvious.