While humans tend to perceive the world through our eyes, dogs rely on their extraordinaty sense of smell. Dr. Horowitz writes: "As we see the world, a dog smells it. The dog's universe is a fascinating place of odors, one on top of the other. The world of scents is as rich a place as the world of sights. "Dogs don't act on the world by handling objects or by eyeballing them, as people might, or by pointing and asking others to act on the object (as the timid might); instead, they bravely stride right up to a new, unknown object, stretch their magnificent snouts within millimeters of it, and take a nice deep sniff."