Animals Souls Are Different in Kind, Not Just Degree

What would you need to see for a counter argument on this point to be compelling? I'd need to see two things. A concrete proposal for a specific mental quality that humans have and other animals on earth don't. And second, i would need to see a compelling philosophical argument for why this quality should be regarded as indicating that souls are different in kind, and not just in degree. Both of these things would be necessary for me: both a specific mental lity that really does distinguish us from animals, and also a compelling philosophical reason behind it. So far, i haven't found any one to day attempting to do those things. The people i'm aware of just tend to repeat old