

Memory is funny. Stuff can play in the background and become familiar without you being consciously aware of it.
It would be possible to do this study without contamination by using completely unknown and newly-released songs as a dataset, and checking against future chart data regarding the popularity, or by examining the reaction of an isolated group of people without constant musical bombardment.
You might like Wesley Willis. https://www.youtube.com/watch?v=4jTPbcnqPxQ