I've done similar experiments with my two cats. Both behaved mostly like dogs - the mirror doesn't smell like a cat nor makes noise like a cat, so why bother with it? I was rather surprised with Siegfrieda ignoring it because she tends to watch whatever I put on the computer screen, be it some "cat game" video or even anime.
That lower emphasis on vision became specially obvious when I showed them videos with kittens meowing. They didn't bother with the screen, but with the speakers.