If they are indeed hearing the music in their heads, for the first time, as one can see a picture in your head as you read a story, then I must say that this makes me so very jealous and does away with the nessecity to have an iPod, or ones hearing for that matter!
.. a bit skeptiKal here...
i've seen some of those who were evaluating
the scores to loose track of a persistent 7/8 conducting,
while telling that they can do this and that, perfect intonation,
with some out of tune performances in their CDs!
mark .. maybe those youngers were listening to melodies,
and found them beauty.
i don't think there's so much people with mental capabilities
of listening/assimilating some harmony tricks unless they have
studied these progressions before, or layering is not too dense.