Does your cat respond when you call their name?

Two of my cats are sisters from the same litter, and they are black. We've been married for sixteen years now and my wife still can't tell them apart. Admittedly, there are times when I get it wrong too. When one of them walks into my office, I'll say, "Hi Cutie" or "Hi Lydia," and if I get the name wrong, she'll stand there looking at me as if I"m crazy. Lydia almost never comes when I call her so it's harder to tell with her, but Cutie often does come. If I'm not paying attention and call her Lydia, she will stop and look at me, and stand there until I correct myself. Then when I call her by her own name, she will continue walking up to me.

I have always called my cats by their names rather than using the generic "kitty, kitty, kitty" call, although I do use that sometimes when they are all outside and I'm trying to get them in, or when it's time to eat, although I seem to have better luck when I call them individually by name.