You know, from the very little I know of attempts at the creation of artificial intelligence, I get the impression that the greatest difficult of the last twenty years or so has been the assumption that these things are necessarily different. The distinction between internally and externally generated sensations and thoughts and emotions and what not are misleading to the extent that one part of the brain generating these things is just a part of the environment to every other part of the brain. Drawing the boundary at our skin makes sense histologically, but it's really the continuum of every part of the body with every part of the world it comes into contact with that generates, at the very least, our recognizable cognitive states. As much as it seems intuitive that we would still experience similar states in a body without the world, and possibly even in a brain without the body, all of these things developed together and are heavily intertwined in a way that we don't usually conceptualize.
It depends on age. A young child can see two apples (sensory) but cannot grasp the concept "two" (cognitive). The normal adult would spend much more time with cognitive activities than pure perception. Conscience experience can be viewed as a continuum (perception, volition, focus, reason, abstraction, concept formation). An interesting research question--how much time over a 24 hr period does the normal person spend in each of these six aspects of conscience experience.
The limit for subjectivity need not be histological, but purely physical. The intervening space from subject to object under observation may be considered internal, and that beyond the object considered external. This involves mentality not limited to the brain.
Especially in an infant does the entire world pecieve as an extension of the child's ego. We adults have remnants of these early sensations modified by more abstract functions. It's abstraction and concept formation for me.
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