I read an article about how much cats depend on order, ritual, patterns and habits. It told the story of a man who said every day at feeding time, his cat heard the can opener, came running and stuck his head over the dish just as the food fell out and onto the top of his head. He wondered why the heck this cat would do such a thing and if he even knew that if he waited a second longer the food would go into the dish and not on his head. The answer was that the cat LEARNED this ritual and that was how he "understood" it worked.
The author added that whenever he used the can opener - regardless if it was cat food or not - the cat could be anywhere in the house and he would come running. It was, the author said, as if the cat was thinking, "Could be food, don't risk not knowing!". I LOVE these critters!