What Do Animals See in a Mirror?
I'm not sure about all cats. My cat ignores mirrors - even previously unseen ones - altogether, at the same time he reacts to youtube videos with cats. However, when he has seen himself in the mirror for the first time in his life he behaved like it was another cat, for two minutes or so.Divide an almost identical uniform background with a piece of glass, block smell and sound if possible. Put two cats on the opposite sides of the glass and observe their reactions.  
Put mirror in the place of glass and observe reactions.  
I can bet the reactions would be drastically different, and not just for cats.