if you have ever read how mp3 compression works, you can easily hear the differences in the 3 samples of each song - by listening for what MP3 emphasizes/keeps.  
There is also "another" clue that will reveal which sample is the high rez version - before you ever hear the first note....!!!!  I won't reveal that here, as others may want to take the test.

MP3 relies on the same human phenomena/tendency that retail stores rely on to sell TV's and speakers... that being: "which one did you notice first or the most" - not necessarily the one that is the most "natural".