Advertising/Marketing and Psychology have a strong correlation. Because of this, many companies and marketing firms use the concepts of classical conditioning to make their advertisements successful. They often manipulate the consumers' emotions. Cigarette companies, such as Camel, are a good example of this. During the mid-1900s, Camel endorsed popular athletes to appear on/in their advertisements. One example of this was when they used Roger Maris to sell their product.
By using Maris, a successful professional baseball player, to sell their products, Camel made people think that, although cigarettes aren't good for you, you can still be successful even if you use them. This is an example of how Camel manipulated your previous emotions/views towards cigarettes. Obviously, this was an effective method because cigarettes are now a large part of our economy.