If we turn now to the input hierarchies of perception, the operations proceed, of course, in the reverse direction, from the peripheral twigs of the tree towards its apex; and instead of trigger-releasers we have the opposite type of mechanisms: a series of filters, scanners or classifiers through which the input traffic must pass in its ascent from periphery to cortex. First you have lateral inhibition, habituation and presumably some efferent control of receptors. On the higher levels are the mechanisms responsible for the visual and acoustic constancy phenomena, the scanning and filtering devices which account for the recognition of patterns in space and time, and enable us to abstract universals and discard particulars. The colloquial complaint: 'I have a memory like a sieve' may be derived from an intuitive grasp of these filtering devices that operate first all along the input channels, then along the storage channels.
How do we pick out a single instrument in a symphony? The whole medley of sounds arriving at the ear-drum is scrambled into a linear pressure-wave with a single variable. To reconstruct the timbre of an instrument, to identify harmonies and melodies, to appreciate phrasing, style and mood, we have to abstract patterns in time as we abstract visual patterns in space. But how does the nervous system do it? I will play you the opening bars of the Archduke Trio; watch your reactions, because no text-book on psychology that I know of will give you the faintest clue [opening bars of Beethoven's Archduke Trio played]. If one looks at the record with a magnifying glass, one is tempted to ask the naive question why the nervous system does not produce engrams by this simple method of coding, instead of being so damned complicated. The answer is, of course, that a linear engram of this kind would be completely useless for the purpose of analysing, matching and recognizing input patterns. The chain is a hopeless model; we cannot do without the tree. «serial vs random access»
In motor hierarchies, an implicit intention or generalized command is particularized, spelled out, step by step, in its descent to the periphery. In perceptual hierarchies, we have the opposite process. The peripheral input is more and more de-particularized, stripped of irrelevancies during its ascent to the centre. The output hierarchy concretizes, the input hierarchy abstracts. The former operates by means of triggering devices, the latter by means of filtering or scanning devices. When I intend to write the letter R, a trigger activates a functional holon, an automatic pattern of muscle contractions, which produces the letter R in my own particular hand-writing. When I read, a scanning device in my visual cortex identifies the letter R regardless of the particular hand that wrote it. Triggers release complex outputs by means of a simple coded signal. Scanners function the opposite way: they convert complex inputs into simple coded signals.
'ABSTRACT' AND 'SPOTLIGHT'
Let me briefly turn to the phenomena of memory and ask whether the hierarchic approach is capable of shedding some additional light on them. You watch a television play. The exact words of each actor are forgotten by the time he speaks his next line, and only their meaning remains; the next morning you can only remember the sequence of scenes which constituted the story; after a month, all you remember is that it was about a gangster on the run or about two men and a woman on a desert island. The same happens generally with the content of novels one has read, and episodes one has lived. The original experience has been stripped of detail, reduced to a schematic outline. Now this skeletonization of the input before it is put into storage, and the gradual decay of the stored material, would mean a terrible impoverishment of memory, if this were the whole story -- memory would be a collection of dusty abstracts, the dehydrated sediments in the wine-glass, with all flavour gone. But there are compensating mechanisms. I can recognize a melody, regardless of the instrument on which it is played, and I can recognize the timbre of an instrument, regardless of the melody played on it. There are several interlocking hierarchies at work, each with its own criteria of relevance. One abstracts melody and treats everything else as noise, the other abstracts timbre and treats melody as noise. Thus not all the information discarded as irrelevant by one filtering system is irretrievably lost, because it may have been stored by another filtering hierarchy with different canons of relevance. Recall would then be made possible by the cooperation of several interlocking hierarchies, which may pertain to different sense modalities -- sight and smell, for instance; or, what is less obvious, there may also be several distinct hierarchies with different criteria or relevance operating within the same sense modality. Recall could then be compared to the process of multi-coloured printing by the superimposition of several colour-blocks. This, of course, is speculative, but some modest evidence for the hypothesis can be found in a series of experiments by J. J. Jenkins and myself; * [14] and more tests on these lines can be designed without much difficulty.
* See Appendix II.
I am aware that the hypothesis is in apparent contradiction to Penfield's [15] experiments eliciting what looks like total recall of past experiences by electrical stimulation of points on the patient's temporal lobe. But the contradiction may be resolved if we include in the criteria of relevance also criteria of emotional relevance which decide whether an input is worth storing. A detail might be emotionally relevant (on a conscious or unconscious level), and retained with almost photographic or cinematographic clarity. One might call this the spotlight type of memory which is stamped in, as distinct from abstractive memory which schematizes. Spotlight memories may be related to eidetic images; and they might even, unlike abstractive memories, originate in the limbic system. [16]
ARBORIZATION AND RETICULATION
I have used the term 'interlocking' or 'interlacing' hierarchies. Of course hierarchies do not operate in a vacuum. This truism regarding the interdependence of processes in an organism is probably the main cause of confusion which obscured from view its hierarchic structure. It is as if the sight of the foliage of the entwined branches in a forest made us forget that the branches originate in separate trees. The trees are vertical structures. The meeting points of branches from neighbouring trees form horizontal networks at several levels. Without the trees there could be no entwining, and no network. Without the networks, each tree would be isolated, and there would be no integration of functions. Arborization and reticulation seem to be complementary principles in the architecture of organisms. In symbolic universes of discourse arborization is reflected in the 'vertical' denotation (definition) of concepts, reticulation in their 'horizontal' connotations in associative networks. This calls to mind Hyden's proposal that the same neuron, or population of neurons, may be a member of several functional 'clubs'.
HIERARCHIC ORDER AND FEEDBACK CONTROL
The most obvious example of interlocking hierarchies is the sensory-motor system. The sensory hierarchy processes information and transmits it in a steady upward flow, some of which reaches the conscious ego at the apex; the ego makes decisions which are spelt out by the downward stream of impulses in the motor hierarchy. But the apex is not the only point of contact between the two systems; they are connected by entwining networks on various lower levels. The network on the lowest level consists of reflexes like the patellary. They are short-cuts between the ascending and descending flow, like loops connecting opposite traffic streams on a motor highway. On the next higher level are the networks of sensory-motor skills and habits, such as touch-typing or driving a car, which do not require the attention of the highest centres -- unless some disturbance throws them out of gear. But let a little dog amble across the icy road in front of the driver, and he will have to make a 'top level' decision whether to slam on the brake, risking the safety of his passengers, or run over the dog. It is at this level, when the pros and cons are precariously balanced that the subjective experience of free choice and moral responsibility arises.
But the ordinary routines of existence do not require such moral decisions, and not even much conscious attention. They operate by means of feedback loops, and loops-within-loops, which form the multilevelled, reticulate networks between
the input and output hierarchies. So long as all goes well and no dog crosses the road, the strategy of riding a bicycle or driving a car can be left to the automatic pilot in the nervous system -- the cybernetic helmsman. But one must beware of using the principle of feedback control as a magic formula. The concept of feedback without the concept of hierarchic order is like the grin without the cat. All skilled routines follow a pre-set pattern according to certain rules of the game. These are fixed, but permit continual adjustments to variable environmental conditions. Feedback can only operate within the limits set by the rules -- by the canon of the skill. The part which feedback plays is to report back on every step in the progress of the operation, whether it is over-shooting or falling short of the mark, how to keep it on an even keel, when to intensify the pace and when to stop. But it cannot alter the intrinsic pattern of the skill. To quote Paul Weiss [17] at the Hixon Symposium:
The structure of the input does not produce the structure of the output, but merely modifies intrinsic nervous activities, which have a structural organization of their own.
One of the vital differences between the S-R and SOHO concepts is that according to the former, the environment determines behaviour, whereas according to the latter, feedback from the environment merely guides or corrects or stabilizes pre-existing patterns of behaviour.
Moreover, the cross-traffic between the sensory and motor hierarchies works both ways. The input guides the output and keeps it on an even keel; but motor activity in its turn guides perception. The eye must scan; its motions, large and small -- drift, flicker, tremor -- are indispensable to vision; an image stabilized on the retina disintegrates into darkness. [18] Similarly with audition: if you try to recall a tune, what do you do? You hum it. Stimuli and responses have been swallowed up by feedback loops within loops, along which impulses run in circles like kittens chasing their tails.
A HIERARCHY OF ENVIRONMENTS
Let us carry this inquiry into the meaning of current terminology a step further, and ask just what that convenient word 'environment' is meant to signify. When I am driving my car, the environment in contact with my right foot is the accelerator pedal, its elastic resistance to pressure provides a tactile feedback which helps keeping the speed of the car steady. The same applies to the 'feel' of the wheel under my hands. But my eyes encompass a much larger environment than my feet and hands; they determine the overall strategy of driving. The hierarchically organized creature that I am is in fact functioning in a hierarchy of environments, guided by a hierarchy of feedbacks.
One advantage of this operational interpretation is that the hierarchy of environments can be extended indefinitely. When the chess-player stares at the board in front of him, trying to visualize various situations three moves ahead, he is guided by feedbacks from imagined environments. Most of our thinking, planning and creating operates in such imaginary environments. But -- to quote Bartlett [19] -- 'all our perceptions are inferential constructs', coloured by imagination, and so the difference is merely one of degrees. The hierarchy is open-ended at the top.
MECHANIZATION AND FREEDOM
A skilled activity, such as writing a letter, branches into sub-skills which, on successively lower levels of the hierarchy, become increasingly mechanized, stereotyped and predictable. The choice of subjects to be discussed in a letter is vast; the next step, phrasing, still offers a great number of alternatives, but is more restricted by the rules of grammar, the limits of one's vocabulary, etc.; the rules of spelling are fixed, with no leeway for flexible strategies, and lastly, the muscle contractions which depress the typewriter keys are entirely automacized. Thus a sub-skill or behavioural holon on the (n) level of the hierarchy has more degrees of freedom (a larger variety of alternative strategic choices permitted by the canon) than a holon on the (n-1) level.
However, all skills tend with increasing mastery and practice to become automatized routines. While acquiring a skill we must concentrate on every detail of what we are doing; then learning begins to condense into habit as steam condenses into drops; with increasing practice we read, write, type, drive 'automatically' or 'mechanically'. Thus we are all the time transforming 'mental' into 'mechanical' activities. In unexpected contingencies, however, the process can be reversed. Driving along a familiar road is an automatized routine; but when that little dog crosses the road, a strategic choice has to be made which is beyond the competence of automatized routine, for which the automatic pilot in my nervous system has not been programmed, and the decision must be referred to higher quarters. The shift of control of an on-going activity from one level to a higher level of the hierarchy -- from 'mechanical' to 'mindful' behaviour -- seems to be the essence of conscious decision-making and of the subjective experience of free will.
The tendency towards the progressive mechanization of skills has its positive side: it conforms to the principle of parsimony. If I could not hit the keys of the typewriter 'automatically' I could not attend to meaning. On the negative side, mechanization, like rigor mortis, affects first the extremities -- the lower subordinate branches of the hierarchy, but it also tends to spread upward. If a skill is practised in the same unvarying conditions, following the same unvarying course, it tends to degenerate into stereotyped routine and its degrees of freedom freeze up. Monotony accelerates enslavement to habit; and if mechanization spreads to the apex of the hierarchy, the result is the rigid pedant, Bergson's homme automate. As von Bertalanffy wrote, 'organisms are not machines, but they can to a certain extent become machines, congeal into machines'. [20]
Vice versa, a variable environment demands flexible behaviour and reverses the trend towards mechanization. However, the challenge of the environment may exceed a critical limit where it can no longer be met by customary routines, however flexible -- because the traditional 'rules of the game' are no longer adequate to cope with the situation. Then a crisis arises. The outcome is either a breakdown of behaviour -- or alternatively the emergence of new forms of behaviour, of original solutions. They have been observed throughout the animal kingdom, from insects onward, through rats to chimpanzees, and point to the existence of unsuspected potentials in the living organism, which are inhibited or dormant in the normal routines of existence, and only make their appearance in exceptional circumstances. They foreshadow the phenomena of human creativity which must remain incomprehensible to the S-R theorist, but appear in a new light when approached from the hierarchic point of view.
SELF-ASSERTION AND INTEGRATION
The holons which constitute an organismic or social hierarchy are Janus-faced entities: facing upward, toward the apex, they function as dependent parts of a larger whole; facing downward, as autonomous wholes in their own right. 'Autonomy' in this context means that organelles, cells, muscles, neurons, organs, all have their intrinsic rhythm and pattern, often manifested spontaneously without external stimulation, and that they tend to persist in and assert their characteristic pattern of activity. This self-assertive tendency is a fundamental and universal characteristic of holons, manifested on every level of every type of hierarchy: in the regulative properties of the morphogenetic field, defying transplantation and experimental mutilation; in the stubbornness of instinct rituals, acquired habits, tribal traditions and social customs; and even in a person's handwriting, which he can modify but not sufficiently to fool the expert. Without this self-assertive tendency of their parts, organisms and societies would lose their articulation and stability.
The opposite aspect of the holon is its integrative tendency to function as an integral part of an existing or evolving larger whole. Its manifestations are equally ubiquitous, from the 'docility' of the embryonic tissues, through the symbiosis of organelles in the cell, to the various forms of cohesive bonds, from flock to insect state and human tribe.
We thus arrive at a polarity between the self-assertive and the integrative tendency of holons on every level. This polarity is of fundamental importance to the SOHO concept. It is in fact implied in the model of th
e multilevelled hierarchy, because the stability of the hierarchy depends on the equilibration of the two opposite tendencies of its holons. Empirically the postulated polarity can be traced in all phenomena of life; in its theoretical aspect it is not derived from any metaphysical dualism, but may rather be regarded as an application of Newton's Third Law of Motion (action and reaction) to hierarchic systems. We may even extend the polarity into inanimate nature: wherever there is a relatively stable dynamic system, from atoms to galaxies, stability is maintained by the equilibration of opposite forces, one of which may be centrifugal or separative or inertial, and the other a centripetal or attractive or cohesive force, which keep the parts in their place in the larger whole, and hold it together. «attractors»
Perhaps the most fertile field of application of the SOHO schema is the study of emotions and emotional disorders on the individual and social scale. Under conditions of stress, the affected part of an organism may become overstimulated and tend to escape the restraining control of the whole. [21] This can lead to pathological changes of an irreversible nature, such as malignant growths with untranimelled proliferation of tissues that have escaped from genetic restraint. On a less extreme level, practically any organ or function may get temporarily and partially out of control. In rage and panic the sympathico-adrenal apparatus takes over from the higher centres which normally coordinate behaviour; when sex is aroused the gonads seem to take over from the brain. The idée fixe, the obsession of the crank, are cognitive holons running riot. There is a whole gamut of mental disorders in which some subordinate part of the mental hierarchy exerts its tyrannical rule over the whole, from the insidious domination of 'repressed' complexes to the major psychoses, in which large chunks of the personality seem to have 'split off' and lead a quasi-independent existence. Aberrations of the human mind are frequently due to the obsessional pursuit of some part-truth, treated as if it were the whole truth -- of a holon masquerading as a whole.