How can we know?

Unfortunately, we can't. Truth be told, I can't even know that you are conscious. That said, I do think that the benefit of the doubt should be given far more then it usually is. The mind is amazing, but the method in which it is made up isn't necessarily all that rare in the world. I would argue that not only does your dog have a mind, but plants likely have a mind as well. Though to a much lesser extent. I'm actually writing a series on the mind, and my latest article goes into why I believe that plants likely have a mind if you are interested.