Ah yes, the natural scavenger, who has evolved to be able to sustain itself on a huge variety of different diets would clearly have a psychological break if they were fed anything other than the correct type of little flavorless brown pellets. You really mean to say that if a dog eats the incorrect type of little flavorless, texturally boring, brown things, that they would develop some type of clinical depression? They eat leaves and grass and twigs, they play with toys that have rolled around in the dirt, they lick everything they can get their hands on, and to top it all off they eat their own shit and vomit. Something tells me they don't have the most refined of taste. Dogs will be just as happy on flavorless brown pellet A as they would on flavorless brown pellet B (unless you can find me some documentation that says otherwise, some sort of research article on the psychological effects of attaining the exact same nutrients from plant sources that they would from meat).