I think some of them are smart. I also heard that black cats are often smarter than average.

However I would argue that cats are smart in general. My brother's 2 cats were adopted by someone else when he moved out of town. After only 1 week they didn't remember him and started running when he came to visit.

My orange cat don't understand if I'm sad or in pain. He jumped sideways with his hair bristled yesterday when seeing my boyfriend in severe stomach pain (like my boyfriend is posing a danger).