Dogs and people have lived together as friends for at least 12,000 years.  Remarkably, it's only been in about the last 20 or 30 years that fundamental questions about WHO dogs are, are being answered by detailed research.  

Take dogs' sensory systems.  It used to be said that dogs are colour blind.  They aren't.  Dogs see colours less distinctly than we do and their vision, when they're looking at something really close, isn't as good as ours.  But they can see distant movement and they can see in dim light much better than we can.  Their hearing is better - about 40 times better.  And then there's smell.  It's a dog's primary way of knowing the world.  Ours is vision, theirs is smell.  Their noses include what's called a vomeronasal organ, that "holds" and recirculates airborne molecules for analysis like a chemistry lab.  Some types of dogs have an olefactory system that's thousands of times more sensitive than ours. Imagine what it would be like to be awash in smells and sounds like dogs are.

And then there's the question of what dogs DO with all this information.  

Do they think in visual images - or maps, or strings of ideas, or perhaps in whole stories? 

Do they think at all?