In the simplistic terms, still thinking, our brain is divided in function between linear, rationalist thought (left brain) and intuitive, wholistic observation in time and space (right brain). The right brain allows us to distinguish a cup and pick it up. The left brain names it "cup". We cannot have a rational discussion without language, which provides structure. As glorious as rationalism is, it is limited by its own structures.
jgnat, that model of brain function (right-brain/left-brain) IS incredibly simplistic (as you admit), as it over-simplifies that which is well-understood by scientists to the point where it offers no real functional utility to neurologists, but arguably only sells pop psychology books to the lay-public (junk science). The actual story of brain functionality is incredibly more complicated than such a broad over-generalization allows.
A similar popular urban myth says that we only use something like 5% of our brains; while accepted by many, it simply is not true, as well.
An example of successful adaptation might be the sense of touch, hearing, and seeing, as structurally they are not too far apart from each other. A blind person would reallocate the brain space with better developed sense of touch and hearing, for instance. Deaf people are keen observers.
Granted, the brain possesses signifant neural plasticity, where it can adopt compensatory mechanisms when a sensory loss occurs (esp if it happens when the person is younger, and brain is still actively developing new synaptic connections amongst the major centers of "higher" functionality where multi-sensory integration takes place). It's a lovely comforting myth to think that the other senses take over to compensate in the event of a loss, but it's not the reality.
