The fascinating thing about dogs is how they have evolved to fill a particular evolutionary niche, that of human companion. As any dog owner will tell you, canines have, or at least appear to have real feelings and can respond to emotions in humans. And they're very clever.
Dogs and humans have developed a symbiotic relationship over the past several thousand years to the point where we both manipulate each other. George Carlin once said that dogs have so much emotional power over us because dogs have eyebrows. And they use them to great effect; to express to humans anger, sadness, happiness.
Think of how dogs had to evolve over time to occupy the place they do now. If you are a Pliestocene human and some animal came over and tried to grab your food, how would you react? But over the years dogs became "smarter," at least in the realm of emotional intelligence. So they could read humans and get them to take the dogs in and actually give them food. It's a brilliant evolutionary strategy. One that the canine ancestor, the wolf, does not posess.
..the canines were given the opportunity to try to remove a piece of meat from under a cage by pulling on a rope in the presence of their caregiver. Dogs and wolves both mastered this promptly. Then the rope was anchored, making it impossible to obtain the meat. The dogs tried a couple of times, then turned to their masters for assistance or cues. The wolves ignored their caregivers, yanking on the rope until exhausted.
"The wolves ... were only interested in the meat," notes Miklosi. "The dogs were of course interested in the meat, but knew that one way to get it might be to figure out what the human wants them to do."