Janus (8 page)

 

* Cf. the ethologist's 'fixed action patterns'.

 

If we descend even further down into the basement of the hierarchy,
we come to visceral processes which are self-regulating, controlled by
homeostatic feedback devices. These, of course, leave little scope for
strategic choices; nevertheless, my conscious self can interfere to some
extent with the normally unconscious, automated functioning of my
respiratory system by holding my breath or applying some Yoga technique.
Thus the distinction between rules and strategies remains in principle
valid even on this basic physiological level. But the relevance of this
distinction will only become fully apparent in later chapters when
we apply it to such fundamental problems as the theory of evolution;
free will versus determinism; and the pathology and creativity of the
human mind.

 

 

 

12

 

 

As already mentioned, the purpose of this chapter is not to provide
a manual of hierarchies, but to convey some idea of the conceptual
framework on which this inquiry is based, and to give the reader the
'feel' of hierarchic thinking as opposed to the current reductionist
and mechanistic trends. To conclude this summary survey, I must mention,
however briefly, a few more principles which all hierarchic systems have
in common.

 

 

One obvious point is that hierarchies do not operate in a vacuum,
but interact with others. This elementary fact has given rise to much
confusion. If you look at a well-kept hedge surrounding a garden like
a living wall, the rich foliage of the entwined branches may make you
forget that the branches originate in separate bushes. The bushes are
vertical,
arborizing
structures. The entwined branches form horizontal
networks
at numerous levels. Without the individual plants there would
be no entwining, and no network. Without the network, each plant would be
isolated, and there would be no hedge and no integration of functions.
'Arborization' and 'reticulation' (net-formation) are complementary
principles in the architecture of organisms and societies. The circulatory
system controlled by the heart and the respiratory system controlled by
the lungs function as quasi-autonomous, self-regulating hierarchies,
but they interact on various levels. In the subject-catalogues in our
libraries the branches are entwined through cross-references. In cognitive
hierarchies -- universes of discourse -- arborization is reflected in the
'vertical' denotation (classification) of concepts, reticulation in their
'horizontal' connotations in associative nets.

 

 

The complementarity of arborization and reticulation yields relevant
clues to the complex problem of how memory works.*

 

* The section that follows is a summary of The Act of Creation,
Book II, Ch. X, The Ghost in the Machine, Ch. V and VI,
and of a paper read to the Harvard Medical School Symposium on
'The Pathology of Memory'. [21]

 

 

13

 

 

In Stevenson's novel
Kidnapped
, Alan Breck makes the casual remark:
'I have a grand memory for forgetting, David.' He speaks for all of us,
and not only those afflicted with aphasia or senility. Painful as it is,
we have to admit that a large proportion of our memories resembles the
dregs in a wine glass, the dehydrated sediments of experiences whose
flavour has gone -- or, to change the metaphor, they are like dusty
abstracts of past events on the shelves of a dimly lit archive.
Fortunately this applies only to one type or category of memories,
which I shall call abstractive memory. But there is another category,
derived from our capacity to recall past episodes, or scenes, or details
of scenes, with almost hallucinatory vividness. I shall call this the
spotlight
type of memory, and I shall contend that 'abstractive memory'
and 'spotlight memory' are different classes of phenomena, based on
different neural mechanisms.

 

 

Take abstractive memory first. The bulk of what we can remember of our
life history, and of the knowledge we have accumulated in the course of
it, is of the abstractive type.

 

 

The word 'abstract' has, in common usage, two main connotations: it is the
opposite of 'concrete', in the sense that it refers to a general concept
rather than a particular instance; in the second place, an 'abstract' is a
condensation of the essence of a longer document. Memory is abstractive in
both senses. I watch a television play. The exact words of each actor are
forgotten within a few seconds; only their abstracted meaning is retained.
The next morning I can only remember the sequence of scenes which constituted
the story. A month later, all I can remember is that the play was about a
gangster on the run. Much the same happens to the mnemic residues of books
one has read and whole chapters of one's own life-story. The original
experience has been stripped of detail, skeletonized, reduced to a
colourless abstract before being confined to the memory store. The nature
of that store is still a complete mystery in brain-research, but it is
obvious that if stored knowledge and experience are to be retrievable (for
otherwise they would be useless), they must be ordered according to the
hierarchic principle -- like a thesaurus or a library subject-catalogue,
with headings and sub-headings but also with a wealth of cross-references
to assist the process of retrieval (the former representing arborization,
the latter the reticulation of the hierarchic structure). If we pursue
for a moment the metaphor of a library representing our memory stores, we
arrive at rather depressing conclusions. Quite apart from the countless
volumes that are left to rot away or fall to dust, there is a hierarchy
of librarians at work who ruthlessly condense long texts into short
abstracts and then make abstracts of the abstracts.

 

 

This process of sifting and abstracting actually starts long before a
lived experience is confined to the memory store. At every relay station
in the perceptual hierarchy through which the sensory input must pass
before being admitted to consciousness it is analysed, classified and
stripped of irrelevant detail.* This enables us to recognize the letter R
in an almost illegible scrawl as 'the same thing' as a huge printed R in a
newspaper headline, by a sophisticated scanning process which disregards
all details and abstracts only the basic geometrical design -- the
'R-ness' of the R -- as worth signalling to higher quarters. This signal
can now be transmitted in a simple code, like a message in Morse, which
contains all the relevant information -- 'it's an R' -- in a condensed,
skeletonized form; but the wealth of calligraphic detail is of course
irretrievably lost, as the inflections of the human voice are lost in the
Morse message. The wistful remark 'I have a memory like a sieve may be
derived from an intuitive grasp of these filtering devices which operate
all along the input channels and storage channels of the nervous system.

 

* The psychologist distinguishes on the lower levels of the hierarchy
lateral inhibition, habituation, and efferent control of the
receptors; on the higher levels the mechanisms responsible for
the visual and auditory constancy phenomena, and the scanning and
filtering devices that account for pattern recognition and enable
us to abstract universals.

 

Yet even the chosen few among the multitude of potential stimuli incessantly
bombarding our receptor organs which have successfully passed all these
selective filters and have attained the status of consciously perceived
events, must submit, as we have seen, to further rigorous stripping
procedures before being admitted to the permanent memory store; and as
time passes, they will suffer further decay. Memory is a prize example
of the law of diminishing returns.

 

 

This retrospective impoverishment of lived experience is unavoidable;
'abstractive memory implies the sacrifice of particulars. If, instead
of abstracting generalized concepts, like 'R' or 'tree' or 'dog', our
memories consisted of a collection of all our particular experiences
of R's and trees and dogs encountered in the past -- a storehouse of
lantern slides and tape -- recordings -- it would be a chaotic jumble,
completely useless for mental guidance, for we would never be able
to identify an R or understand a spoken sentence. Without hierarchic
order and classification, memory would be bedlam (or the parroting of
sequences learned by rote, and reinforced by conditioning, which is the
behaviourist's model -- or caricature -- for remembering).

 

 

To say it again: the loss of particulars in abstractive memory is
unavoidable. Fortunately this is not the whole story, for there are
several compensating factors which, at least in part, make up for
the loss.

 

 

In the first place, the abstractive process can acquire a higher degree
of sophistication by learning from experience. To the novice, all red wines
taste alike, and all Japanese males look the same. But he can be taught
to superimpose more delicate perceptual filters on the coarser ones,
as Constable trained himself to discriminate between diverse types of clouds
and to classify them into sub-categories. Thus we learn to abstract finer
and finer nuances -- to make the trees of the hierarchies of perception
grow new shoots, as it were.

 

 

Moreover, it is important to realize that abstractive memory is not based
on a single hierarchy but on several interlocking hierarchies pertaining
to different sensory realms such as vision, hearing, smell. What is less
obvious is that there may exist several distinct hierarchies with different
criteria of relevance operating within the same sense modality. I can
recognize a melody regardless of the instrument on which it was played;
but I can also recognize the sound of an instrument regardless of the
melody played on it. We must therefore assume that melodic pattern and
instrument sound (timbre) are abstracted and stored independently by
separate filtering hierarchies
within the same sensory modality but with
different criteria of relevance
. One abstracts melody and disregards
timbre, the other abstracts the timbre of an instrument and disregards
melody as irrelevant. Thus not all the detail discarded as irrelevant
by one filtering system is irretrievably lost, because it may have been
retained and stored by another filtering hierarchy with different criteria
of relevance.

 

 

The recall of an experience would then be made possible by the cooperation
of several interlocking hierarchies, which may include different sense
modalities, for instance, sight and sound or odour, or different branches
within the same modality. You may remember the words of the aria 'Your Tiny
Hand is Frozen', but have lost the tune. Or you may remember the tune
after having forgotten the words. And you may recognize the unique timbre
of Caruso's voice on a gramophone record, regardless of the words and
the tune he is singing. But if two, or all three of these features have
been abstracted and stored, the recall of the original experience will
have more dimensions and be the more complete.

 

 

The process could in some respects be compared to multi-colour printing
by the superimposition of several colour-blocks. The painting to be
reproduced -- the original experience -- is photographed through
different colour-filters on blue, red and yellow plates, each of
which retains only those features that are 'relevant' to it: i.e.,
those which appear in its own colour, and ignores all other features;
then they are recombined into a more or less faithful reconstruction of
the original input. Each hierarchy would then have a different 'colour'
attached to it, the colour symbolizing its
criteria of relevance
.
Which memory-forming hierarchies will be active at any given time depends,
of course, on the subject's general interests and momentary state of mind.

 

 

Although this hypothesis represents a radical departure from both the
behaviourist and the Gestalt schools' conceptions of memory, some modest
evidence for it can be found in a series of experiments carried out in
cooperation with Professor J. J. Jenkins in the psychological laboratory
of Stanford University;* and more tests on these lines can be designed
without much difficulty.

 

* See Appendix II. This is a rather technical paper of possible
interest to experimental psychologists, which the general reader
can safely ignore. The gist of the experiment was to show to each
subject for a fraction of a second only (by means of an apparatus
called a tachistoscope) a number of seven or eight digits, and
then let him try to repeat the sequence. The results of several
hundred experiments show that a highly significant number of errors
(approximately fifty per cent) consisted in the subject correctly
identifying all numbers in the sequence, but inverting the
order of two or three neighbouring digits. This seems to confirm
that the identification of individual digits, and the determination
of their sequential order, are carried out by different branches
of the perceptual hierarchy.

 

 

14

 

 

The 'colour printing' hypothesis may provide part of the explanation
of the complex phenomena of memory and recall, but it is based solely
on the abstractive type of memory which by itself cannot account for
the extreme vividness of the 'spotlight' type of memory mentioned at the
beginning of this chapter. It is a method of retention based on principles
which seem to be the exact opposite of memory formation in abstractive
hierarchies. It is characterized by the recall of scenes or details with
almost hallucinatory clarity. They are rather like photographic close-ups,
in contrast to abstractive memory's aerial panorama seen through a haze.
The emphasis is on detail, which may be a fragment, torn from its context,
that survived the decay of the whole to which it once belonged -- like the
single lock of hair on the shrivelled mummy of an Egyptian princess. It may
be auditory -- a line from an otherwise forgotten poem, or a chance remark
by a stranger overheard in a bus; or visual -- a wart on Nanny's chin,
a hand waving farewell from the window of a departing train; or even
refer to taste and smell, like Proust's celebrated madeleine (the French
pastry, not the girl). Though often trivial from a rational point of
view, these spotlighted images add texture and flavour to memory, and
have an uncanny evocative power. This suggests that, although irrelevant
by logical criteria, they have some special emotive significance (on a
conscious or unconscious level) that caused them to be retained.