Humans tend to classify objects by shape first and then use other aspects to further specify them and turn them into abstract concepts. Dogs start with size and then rely on texture. You and I see a marble and a basketball as two examples of balls. A dog would consider the marble to be more like a small, smooth coin. It would be hilarious to have a philosophical conversation with a dog with human-level consciousness.
Researchers have provided the first empirical evidence that the way in which dogs relate words to objects is fundamentally different to humans.