All advertisements try to manipulate us to buy their products. Many ads use positive things to advertise their products by using famous actors or actresses, or using attractive women to sell something sexy or appealing (alcohol, perfume, etc..)
The advertisement I found online (Go to this link ---->>> http://www.flickr.com/photos/duvalguillaume/2360107161/ to check it out) uses a negative image to make us want to buy their product. The ad used a man in a full body cast to sell bicycle helmets. The advertisement agency's purpose was to show that the man was wearing a helmet because his head was not covered with a cast. Since he was wearing their helmet, he was not killed, but the rest of his body was injured. If we wear their helmet, then our head would be protected for injuries.
In regards to Classical Conditioning that we learned in class... CS (helmet) --> UCS (uninjured head but the rest of the body is in a cast) --> UCR (We are happy that our head wasn't damaged in the accident) --> CR (If we wore the helmet, our heads would be protected from harm.)... I hope I got that right!
If you want to look at the website where I got the picture from go to this website http://spyrestudios.com/hilarious-print-ads/ The ads are really funny.