They totally understand it. Mine would open gifts early, knock the ornaments off or walk around the house with strands of tinsel hanging out of their arses. That is our public service announcement for the day - if you have cats - don't put tinsel on the tree! Cats think that if it's shiny, and can be eaten - then it SHOULD be eaten. I am at a loss to explain why Darwin did not dispense with them eons ago.