In 1999, researchers put these kinds of messages to the test in a British supermarket by changing the store music (the supraliminal stimulus) on alternating days in order to encourage customers to buy either French or German wine.
Sure enough, when German music played, German wine outsold French wine, and when French music played, French sales were higher.
Questionnaires filled out by shoppers afterward demonstrated that they were aware of the music but unaware of the effect that it seemed to have on their behavior.
