I've read this before. That's why I think the question "do animals have consciousness?" is meaningless, because "consciousness" usually implies "like ours." They have something that probably bears some relationship to ours. Some birds have a "theory of mind" where they know what you know, e.g. whether you saw them hide the food. It would be possible (maybe someone's already done it?) to enumerate the N tests of "cons…
This is the problem of describing if a gradient has something. Quite often the 'N tests' we make up end up excluding entire classes of humans (You're blind, oops!) by poor premise in our classifications.
People love black and white/binary classification systems, the problem with reality is it rarely gives a damn about giving us simple systems to classify that way.