I grew up with barn cats, so we until I had my own kitties, I didn't realize how smart and discerning cats are. A school friend of mine was the first person to tell me that when cats are relaxed and happy, their ears are held horizontally to the sides of their heads (as opposed to back).
A couple of years ago I lost a cat for 10 months. I think someone stole him as he disappeared 1 week before Xmas. When he returned, he was sitting in my backyard. I called him and brought him inside. I didn't really know before then that cats can be exceedingly happy. He definitely was overjoyed at coming home and if he could, he would have been smiling. His body language said a whole lot.
I grew up on a farm so they didn't get a lot of anything from us other than us petting our favourite (tame) ones and searching for new kittens in the hay mow. People will think me kind of sadistic, but in the summer when haying season was in, I would hunt mice under the bales in the field and take them to mother cats and/or kittens to eat.