The Day the Universe Changed - James Burke [152]
A very large number of these signals arrive in the visual field of the brain, where the object is ‘seen’. It is at this point that the object first takes on an identity for the brain. It is the brain which sees, not the eye. The pattern of signals activates neurons whose job it is to recognise each specific signal. The cognition or comprehending of the signal pattern as an object occurs because the pattern fits an already existing structure. Reality, in one sense, is in the brain before it is experienced, or else the signals would make no sense.
The brain imposes visual order on chaos by grouping sets of signals, rearranging them, or rejecting them. Reality is what the brain makes it. The same basic mechanism functions for the other senses. This imposition of the hypothesis on an experience is what causes optical illusions. It also modifies all forms of perception at all levels of complexity. To quote Wittgenstein once more, ‘You see what you want to see.’
All observation of the external world is, therefore, theory-laden. The world would be chaos if this were not so. A good example of this is the case of the visual illusion formed of black and white blobs, illustrated here.
This picture is chaotic until the observer imposes the hypothesis that it contains a Dalmatian dog, whereupon the animal becomes visible
Gestalt illustrations. Top left, Necker cubes; top right, the Boring young girl/old hag; bottom left, the Rubin vase; bottom right, the Jastrow duck/rabbit.
When the illustration is orderly but ambiguous, the preferred view, or Gestalt, will choose between the available alternatives. In the examples above, even though the Gestalt may be switched, enabling the observer to see the alternative version, only one of the alternatives can be seen at a time.
Perception is also coloured by value judgements. In the Necker cube illustration, the word which has unpleasant connotations will be seen on the rear wall of the cube, while the one with acceptable overtones will appear on the front.
Observation is similarly dependent upon context in the case of specialist data, where the illustration will have meaning only to the initiate. Terrain which, to a geographer, is recognisable on a map, will appear to the amateur only as a series of lines. The tracks left by particles fragmenting in a bubble chamber are meaningful only to a physicist.
In all cases of perception, from the most basic to the most sophisticated, the meaning of the experience is recognised by the observer according to a horizon of expectation within which the experience will be expected to fall. Anything which does not do so will be rejected as meaningless or irrelevant. If you believe that the universe is made of omelette, you design instruments to find traces of intergalactic egg. In such a structure phenomena such as planets or black holes would be rejected.
Tracks in a bubble chamber, so called because the particles which are fired into the chamber leave trails of minute bubbles in liquids such as propane, held in the chamber under high pressure.
This is not as far-fetched as it may seem. The structure, or Gestalt, controls all perceptions and all actions. It is a complete version of what reality is supposed to be. It must be so if the individual or group is to function as a decision-making entity. Each must have a valid structure of reality by which to live. All that can accurately be said about a man who thinks he is a poached egg is that he is in the minority.
The structure therefore sets the values, bestows meaning, determines the morals, ethics, aims, limitations and purpose of life. It imposes on the external world the contemporary version of reality. The answer therefore to the question, ‘Which truth does science seek?’can only be, ‘The truth defined by the contemporary structure.’
The structure represents a comprehensive