To put my question a different way: how confident are we in our current map of the system?
I'm asking as a legitimately curious layperson. Perhaps this comment is naive, and if so, I'm admitting to my naivete in advance.
no. (sensory neuroscience guy here)
But, it turns out that performance at a huge variety of sub-tasks is highly correlated. E.g. reaction time (catch a falling ruler as fast as you can) correlates with ability to solve math problems, which correlates with ability to control impulses.
This is why IQ, as a general measure that covers a wide variety of tasks, is so useful. (Of course, that's not to say IQ covers everything about cognition in some absolute way; it doesn't measure ability to balance on a beam, for example, AFAIK).
A simple model of (higher) consciousness could be that it is simply the 'state of the brain'. Sensation would be an almost axiomatic as the 'pattern of state change for specific stimuli' whereas 'thought' is 'pattern of state change invariant of stimuli'.
Cognition could then be defined as 'sensation that [evokes] thought'.