My opinion is that the difference between human beings and (other) animals is qualitative rather than quantitative (continuum). It seems obvious based on behaviour alone that no other species is capable of the kind of thinking human beings can do. Some animals might be self-aware to some extent but I highly doubt that any other species is capable of abstract thought or moral reasoning etc. Animals seem to be stuck at the present moment and immediate concerns such as eating, mating and protecting themselves.

They act on impulse and based on what kind of stimulus is currently concerning them. Some animals such as chimps can learn little bit of language but I remember coming upon a nice quote about chimps and their language ability saying that while they can learn some language, they never seem to have anything to say. This is exactly what one would expect if chimps (and other less intelligent animals) are merely living in the moment and from one impulse to the next. They have no actual thoughts. Humans are truly special and I have no idea why this happens to be so.