As we go from simple to more complicated aspects of mentality, we enter vaguer and vaguer territory, where the terms we use become more difficult to travel with. Thinking is certainly one of these. And to say that consciousness is not necessary for thinking makes us immediately bristle with protest. Surely thinking is the very heart and bone of consciousness! But let us go slowly here. What we would be referring to would be that type of free associating which might be called thinking-about or thinking-of, which, indeed, always seems to be fully surrounded and immersed in the image-peopled province of consciousness. But the matter is really not that clear at all.
Let us begin with the type of thinking that ends in a result to which may be predicated the terms right or wrong. This is what is commonly referred to as making judgments, and is very similar to one extreme of solution learning that we have just discussed.
A simple experiment, so simple as to seem trivial, will bring us directly to the heart of the matter. Take any two unequal objects, such as a pen and pencil or two unequally filled glasses of water, and place them on the desk in front of you. Then, partly closing your eyes to increase your attention to the task, pick up each one with the thumb and forefinger and judge which is heavier. Now introspect on everything you are doing. You will find yourself conscious of the feel of the objects against the skin of your fingers, conscious of the slight downward pressure as you feel the weight of each, conscious of any protuberances on the sides of the objects, and so forth. And now the actual judging of which is heavier. Where is that? Lo! The very act of judgment that one object is heavier than the other is not conscious. It is somehow just given to you by your nervous system. If we call that process of judgment thinking, we are finding that such thinking is not conscious at all. A simple experiment, yes, but extremely important. It demolishes at once the entire tradition that such thought processes are the structure of the conscious mind.
This type of experiment came to be studied extensively back at the beginning of this century in what came to be known as the Würzburg School. It all began with a study by Karl Marbe in 1901, which was very similar to the above, except that small weights were used. The subject was asked to lift two weights in front of him, and place the one that was heavier in front of the experimenter, who was facing him. And it came as a startling discovery both to the experimenter himself and to his highly trained subjects, all of them introspective psychologists, that the process of judgment itself was never conscious. Physics and psychology always show interesting contrasts, and it is one of the ironies of science that the Marbe experiment, so simple as to seem silly, was to psychology what the so-difficult-to-set-up Michaelson-Morley experiment was to physics. Just as the latter proved that the ether, that substance supposed to exist through-out space, did not exist, so the weight-judgment experiment showed that judging, that supposed hallmark of consciousness, did not exist in consciousness at all.
Julian Jaynes, “The Origin Of Consciousness In The Breakdown Of The Bicameral Mind”