Last Christmas, I gave you my heart, but the very next day you gave it away. This year, to save me from tears, I'll give it to someone special... And so on, and so on. I'm sure, you do know the lyrics. Almost everyone do. One of the main reasons, why do we know Christmas songs so well, is that every year they repeat so many times that you unconsciously learn both, the melody and the lyrics. Even if you don't like all those super happy Christmas songs when you first heard it, it's more than probable that after a few years you will start first humming it, then singing it and finally loving it. It's because of the so called 'exposure effect'. The scientists claim that the more often we hear a particular song, the more we like it. So if you still don't like Christmas music, just keep listening to it!