Dr. Casey Blood's excellent book Science, Sense and Soul reports an interesting experiment on so-called split-brain patients -- that is, people who have had their corpus callosum surgically cut, effectively cutting off communication between the right and left hemispheres of the brain.
The experiment took advantage of the fact that visual stimuli perceived by the left eye are processed by the right hemisphere, and vice versa. So in these patients, what is seen by the left eye is known only to the right side of the brain.
The other salient fact is that the left hemisphere is responsible for speech, while the right side is incapable of verbalization.
Dr. Blood reports:
In this experiment, different pictures were shown to the two sides of the brain.... The right, nonverbal, side was shown a winter scene. From among four choices of pictures -- a snow shovel, a chicken, a leaf, and a pen -- the left hand, controlled by the right side, pointed to a snow shovel.
The left, verbal, side was shown a picture of a chicken's claw. The right hand, controlled by the left side, chose, from among the same four choices, a picture of a chicken.
This was just as expected, showing that each half of the brain was intelligent. When asked why the nonverbal hand pointed to a snow shovel, however, the split-brain patient -- via the verbal side, which was not aware of the winter scene sent to the nonverbal side but was aware of the "nonverbal" hand pointing to the snow shovel -- said, seriously, "Oh, that was to shovel out the chicken coop."
An association was manufactured by the verbal half in this example ... to preserve the appearance of rationality. The question is, how much of our own daily thinking involves these manufactured, spurious associations, even though the two halves of a normal brain communicate quite well? More than we suspect or wish, I would guess.
There is one other point that this experiment illustrates to the mystic. The information that the nonverbal side had was correct, but because the information did not go through the rational, verbal apparatus, the verbal side did not trust the nonverbal information. In just the same way, we rationalize away -- ignore, distort -- intuitive information because it does not come through our rational, verbal apparatus. [pp. 146-147]
It is indeed interesting to consider how much of our thinking is bound up in in rationalizations that have only a superficial appearance of logical analysis. Like the author, I suspect that we often exert considerable mental energy in finding reasons to explain or justify to ourselves the things that we already know (or think we know).
Casey Blood, by the way, is a physicist who became interested in mysticism -- specifically Sufism, a form of Islamic mysticism -- and spent many years studying it. In the process, he investigated the science of neurology in order to formulate a theory about how the higher mind may influence and operate through the nervous system. His thoughts on this and on the possible relationship between quantum physics and mystical cosmology are unusually lucid, presented without any of the the vagueness and obfuscation ordinarily found in such discussions. Whether or not his interpretation of quantum mechanics is correct I cannot say, but it is certainly thought-provoking. And it is explained in language that even an uninformed layman like me can understand without the slightest difficulty. In fact, it's probably the clearest exposition of the wave/particle duality problem I've ever read.
I highly recommend his book.