Blind Guardian
Member
Or you know, just changing in musical preference without any reflection to their maturity or intelligence.
Do you really believe that? Good metal is the type of music you can concetrate wholly on and enjoy almost forever, while you'll get tired of this song after a couple of plays at most. You can differentiate advanced music from less advanced music just like you can tell the difference between a childrens book and a book for adults.
I'm not saying that it's more intelligent to listen to one type of music, but I do mean that listening to My Morning Jacket, as opposed to metal, indicates that you're less interested in music overall.