Can you be more explicit about your question and perhaps to the particular words or sub-phrases you don't follow. I mean no disrespect but I'm lost as how to answer you.
Sure, I'll unpack that for you.
You're pointing out that the problem with comparing private behaviours is that they're private; we don't have direct access to them, so we can't directly quantify them. So when you ask, how can I know if a private behaviour of one individual is like a private behaviour of another individual, I need to know what you mean by that question.
If you mean, does it produce similar public behaviour, that's easy; I'll run some tests and see.
If you mean, does it produce similar patterns of neural activity, that's easy. I can put both subjects in FMRI scanners and see what's going on inside their heads.
If you mean, does it produce similar associations in the minds of the two subjects, that's easy. I'll just ask them. If one reports that the colour blue invokes feelings of serenity, and the other one feelings of panic, then clearly the experiences differ in that regard.
My point is, if you want me to tell you how I can know if the two experiences are similar, you have to tell me first what it would mean for them to be different.
Blue is a physical property. Looking at something blue is a physical process; so too is recalling a memory related to the colour. The very experience of blue is a physical process. So any question of similarity or difference can be reduced to objective physical concepts, regardless of the fact that we're discussing private behaviours.
It's just that the human brain is the third* most complex device known, so while this is possible in principle, it's not at all easy in practice.
The broader point I'm trying to make is twofold. First, it's perfectly obvious that consciousness comes from brains (working within their environment, if you're a behaviourist) and no mystical magical additional substance is required to explain our observations, that further, there is simply no room for any mystical magical additional substance. Neurophysiology and neurochemistry show us that messing with the brain systematically messes with the mind such that dualism and consciousness idealism have no gaps left to be god of.
Observation tells us that minds is what brain does. But it doesn't give us a philosophical underpinning of how this can happen, how a mere meat machine can produce something as abstract as subjective experience. That's where Dennett and Hofstadter's self-referential information processing comes in - the strange loops that gave that book its title. This is my second point, that self-reference gives information processing systems access to a qualitatively different set of behaviours that cannot even be simulated by a system without self-reference, and that the set behaviours arising from self-reference maps to the set of behaviours we label
consciousness.
Since you've read Hofstadter, this will already make sense to you. Certain others here refuse to allow one or the other (or both) of these facts, though never do we see a coherent reason for their objection (or at least, never a coherent reason that isn't factually false).
The argument has been going round and round for years. Most of the people arguing contrary to me have me on ignore by this point, because I have no truck with the nonsense they're peddling and tell them so. I don't consider it a waste of time, though, because I'm not the only one arguing on the side of reality, and everyone brings their own field of expertise to the table, so we can all learn from it.
And every so often, someone gets it, and changes their mind.
* Or maybe fifth, depending on how you grade complexity, or even lower depending on how specific you want to be.
