I'm pretty sure my dogs thoughts go something like this:
''Birds! run run run bark bark bark chase chase chase!''
"Cats! I hate you cats!"
"Lawn mower! If it bite it it will run away!"
"Hungry now, feed me, stroke my belly.....Hey did I say you could stop stroking my belly???!"

I think dogs are pretty intelligent but it's just that we don't see it because they have a different language and means of communication. Dogs greet each other in their own way and they also decide on who is the leader of the pack. They follow a certain structure. They definitely think logically in some way. It would be nice if we can dig deep into their thoughts.

Dogs can be very smart to the best of my knowledge. All that is based on what you teach them to do and interpret in their own way. It's why we have military dogs that goes to war and fight with the army. 

Nobody knows what these animals think but I do know that they feel emotions and w dig could be sad  or happy and uses their actions to let you know how they feel.