Cats react to the can opener sound for a couple of reasons. 1) They love tuna and people like me who love cats succumb to the temptation of feeding them once in a while to feeding them tuna. Tuna is not good for cats, it has little nutrient value for cats and drains them of vital Vitamin D. 2) People feed cats canned food. Canned food is garbage, total garbage BUT they have additives that make cats like them, much as all the junk food humans consume. So yes, you open a can and they come running. Sad though, you are just feeding them rubbish, running to the veterinarian every 3 months, getting them drugs that only further destroy their health, and shorten their life. Feed them raw food, it is not so complicated, make an effort (I realize it is easier to open a bag of friskies and throw it in a dish as opposed to getting fresh chicken/beef and cutting in small pieces, adding needed supplements and feeding them). But… the rewards are there. Always had to run to the vet years ago when I fed them kibbles and canned food (although I will agree that there are some healthy natural brands that do make good cooked/canned foods for cats). Kibble however, is not good, in any form or shape. The last 10 years on raw, I haven’t had an issue. So yes, a can opener, much as opening a “treats” bag… gets them running, all for the wrong reason… eating garbage. Cats get addicted (or are made addicted to as humans) to junk food. Sad.