Huh. I always just thought it was because my cat isn't smart enough to differentiate between "can noise, human making tuna sandwich" and "can noise, human is dispensing cat food."
To me, the weird thing is that my cat knows the sound of a can opener at all.
We got her when she was waaaaay too young. Someone abandoned her on the vet's doorstep. She has never known that a can opener means food because for her entire life, she has been fed canned food with a pop-top.
But still, when I pull out the can opener to open some vegetables, she comes running.
I have no idea why, but it's one of those things that makes me think that knowledge can be encoded in DNA and passed down through generations.
One of our cats will run into the kitchen any time someone opens up tuna, or warm butter, or mayonnaise. That's scent.
She makes a noise which summons all the other cats.
She doesn’t mind whether it’s salmon, tilapia or whatever. She is summoned as if by a spell.