Psychologists spend many research hours studying this sort of thing for major corporations. One example of this are the radio stations in your town. Chances are they're all holding contests of one kind or another right now. To the people who work at those stations, their contests are all very different, some better or more exciting than contests on other radio stations. I'll bet that you, as an average listener, don't really notice the difference.
All contests start to sound the same.
Studies have shown that the people who win those contests can't even remember which station they won from a year down the road. There isn't enough noticeable difference. On the other hand, Just Noticeable Difference can work the other way. As an expert on chair manufacturing, I know that my chair isn't as good as Marsha's, but my customers don't really notice the difference. Now this whole concept is very upsetting to some people.