When I was in jail for assault a few years ago, there was a guy who bought some coffee with his commissary money. My cellmates began to snort the coffee like it was cocaine. It seems they were desperate for anything resembling the form of drugs, even when it was merely a pastiche of the addiction itself. In dogs (and raccoons; rarely some cats), a similar behavior is seen: whence there is no available luxury foods, they may begin to scour the trash for chicken, pizza crust, or whatever else they can find, strewing it across the floor. A dog with a stick addiction may resort to increasingly smaller twigs for its amusement when it becomes desperate enough.
Dogs must eat, just as humans do; but, there is a certain type of dog who begs excessively, who can think of nothing but food. (Freud wrote of a similar tendency in humans who were deprived of tobacco, who would dream of mountains upon mountains of tobacco. [1]) His attention is constantly devoted to the possibility of being fed, and he begs when one enters the kitchen even when there is nothing to feed him but the same old food he eats every single day. Indeed, life is boring even for animals. It is an unfortunate reality that even if a cat or a parrot could learn the workings of a computer, their impoverished body types prevent them from making any use of that knowledge.
We do not reprimand a dog for simply wanting special foods, but we do so when they beg for it; i.e., we are willing to satiate their drives, but only when we deem the setting appropriate to do so. When their obsession becomes extreme, dogs may begin to dig in the trash.
A more general account of animal cathexis is needed still.
Endnotes
"Eating and drinking constituted the pivot around which most of our dreams revolved. One of us, who was especially fond of going to big dinner-parties, was delighted if he could report in the morning "that he had had a three-course dinner''. Another dreamed of tobacco, whole mountains of tobacco; yet another dreamed of a ship approaching on the open sea under full sail. Still another dream deserves to be mentioned: The postman brought the post and gave a long explanation of why it was so long delayed; he had delivered it at the wrong address, and only with great trouble was he able to get it back. To be sure, we were often occupied in our sleep with still more impossible things, but the lack of fantasy in almost all the dreams which I myself dreamed, or heard others relate, was quite striking."
- Freud, The Interpretation of Dreams, p. 31