The intelligence of dogs : canine consciousness and capabilities

"Do dogs of different breeds differ in intelligence? How well do they understand human language, and do they have a language of their own which humans can learn to understand? Do dogs have memories of things past and images or anticipations of things to come? Do they have feelings such as guilt, loyalty, and protectiveness or even simple emotions such as joy and sorrow? Or are these human terms for entirely different animal behaviors? In The Inte...