Why don't cats react to their reflections?

To: Matmail:

Our cat, Harley, always reacts to the presence of another cat. Why doesn't he react to his own reflection in a mirror? Your clarification of this question may save my marriage.

-- dt french, the Net

After pawing through the Matthew Alice Archive of Grocery Coupons and Cat Facts, we think we can save the Frenches a trip to annoying old divorce court. Harley is one among the huge group of animals that hasn't a clue that they're looking at themselves when they look in a mirror. Only apes and humans are smart enough to figure that out. We know this because scientists have wasted many years putting creatures in front of mirrors and watching them react. Birds, especially males, often get annoyed. They'll attack the invader's image. Cats and dogs react unpredictably. They'll hiss, bark, stare, sniff, try to play, fall asleep, run away, investigate, do absolutely nothing. It seems to depend on the personality of the individual animal. This is not to say that Harley is smarter than the average cat. More likely, Harley just needs extra cues before he reacts. Odor, f'rinstance. Or the sound of a trespasser's little cat feet. If the mirror image doesn't smell or sound like an alien feline, he's not interested. Like many cats, he probably learned early on that if he ignores the cat in the mirror, it goes away.