Have you ever had the experience of sharing food with a dog when begging for food? Or buy snacks for dogs from supermarkets or pet shops, take them out of plastic bags at home, call the dog's name and tell him to buy delicious food for him? Dogs have memories. If they had had such an experience before, they would have formed in his mind. What you eat is delicious. If I want it, my master will give it to me. If you don't give it to me, you will scream. If you are bored, the host will share it with me. When the plastic bag rings, he will think that the delicious food is coming again.