The Act of Creation (75 page)

 

 

Perceptual matrices function not only autonomously, but display
considerable 'self-assertion'. This is shown in a simple but drastic
manner by the difficulty of breaking the arrow illusion:

 

 

Another example of 'self-assertion' is the tiresome insistence with which
a tune will go round and round in your head; or the infuriating messages
-- 'I told you so' -- 'I told you so' rapped out at the rate of once
per second by the wheels of your railway-carriage. A more advanced but
equally typical illustration for 'knowing is seeing' is this quote from
Babbage: 'I will prepare the apparatus, and put you in such a position
that [Fraunhofer's dark lines] shall be visible, and yet you shall look
for them and not find them: after which, while you remain in the same
position, I will instruct you
how to see them
, and you shall see
them, and not merely wonder you did not see them before, but you shall
find it impossible to look at the spectrum without seeing them.' [18]

 

 

A pretty illustration of perception impregnated by previous knowledge
is in the drawing opposite.

 

 

The bear climbing on the other side of the tree is purely inferential.
Yet you
see
the semi-circles plus four strokes as his paws.

 

 

Levels of Memory
Perception and memory cannot be un-scrambled. Let us consider briefly
a few types of 'mnemic' processes which intervene on various levels of
the hierarchy.
On the lowest, peripheral level we find automatisms designed to reduce
redundancy and to 'compress' the input. It would be uneconomical if
each receptor in the retina would signal to report stimulation from a
uniformly illuminated area; hence lateral inhibition between neighbouring
receptor units, combined with light-adaptation, will filter down the input
to signals which report only the relevant spatial
differences
in
illumination -- i.e. the contours of the illuminated area. [19] Likewise,
the eye adapts to uniform motion -- as seen in the illusion of reverse
movement when the real movement stops (the 'waterfall-illusion'). These
automatisms could be called memory processes confined to the psychological
present (in the broad sense of 'memory = modification of responsiveness
by experience').
More lasting are after-images -- once regarded as the prototypes of
'photographic' memory. In fact, however, the after-image 'improves' on the
original by achieving greater regularity and simplicity. Goethe was the
first to observe that the after-image of a square will gradually become
transformed into it circle -- a figure of greater symmetry. Rothschild's
[20] experiments showed that only regular figures with 'good' contour
produce stable after-images; that figures with gaps in their contours
appear 'closed' in the after-image; that small irregularities disappear,
and elements which 'do not belong' to a figure, such as a squiggle or
tail attached to a square, become detached from it and come and go as
independent units. Thus the reproduction is far from mechanical, and is
controlled both by intrinsic codes and from higher centres. [21]
There are some significant parallels between after-images and images
which have been artificially stabilized on the retina. The latter are
obtained by a tiny projector, mounted on a contact-lens worn by the
subject. The illuminated target-figure is fixed at the other end of the
projector; it moves with the involuntary scanning motions of the eyeball,
and its projection remains thus fixed on the same spot of the retina --
subtending a visual angle of two degrees in a patch of light of five
degrees, with darkness all round. Under these conditions the perceived
image will vanish and reappear much as after-images do -- either as a
whole, or it will disintegrate into parts. If the latter is the case,
the fragments will be meaningful in one way or the other: a human
face will break up into its specific features or groups of features --
profile or top of the head; and a composite monogram will break up into
the individual letters and numbers which were hidden in it. Conversely,
the elements in a meaningless pattern of curlicews will at first fade and
reappear in varions combinations; but after a while they will organize
themselves into stable sub-wholes. Central processes fraught with past
experience exert an obvious influence on these phenomena; and so does
the subject's attitude.
The next step leads to
eidetic images
. These occupy an intermediate
place in the memory hierarchy between after-images and the 'picture-strip'
type of recall. In their direct sensory impact they are comparable to
hypnagogic images and close to hallucinations. The experimenter directs
the subject to inspect a picture for about thirty seconds without staring
(to eliminate after-images), then to look at a grey screen. The average
person sees nothing; the eidetic 'projects' the image onto the screen
and behaves as if the picture were actually there. He can focus on a
detail, point out its exact position on the screen, count the buttons
on a coat, the number of spokes on a wheel, and 'read' the letters in a
foreign-language text forward or backward. [22] It seems, therefore,
that eidetic images 'are seen in the literal sense of the word'. [23]
Eidetic recall may be limited to a short interval after inspecting an
object or picture, or extend to 'minutes, days, years'. [24] Analogous
phenomena seem to exist in other sense-modalities: Beethoven, Mozart,
Wagner, and Elgar were supposed to be able to 'hear at will the full
texture of an orchestra'. [25]
Eidetic memory, though rare in adults, seems to be quite common
in children before puberty; 'in certain regions,' according to
Kluever, 'eighty to a hundred per cent of the children are reported
eideletic'. [26] This is a striking confirmation of the commonplace
that the child lives in a world of images of great vividness, whereas
the average adult's images are grey shadows. The eidetic type of memory
seems to be irretrievably lost, in all but exceptional cases, with
the transition from the perceptual and affective to the conceptual
and symbolic mentality. Pictorial memory, as we saw, belongs to a
phylogenetically and ontogenetically earlier level of the mnemic
hierarchy.
Yet if we expect the eidetic image to be a true photographic record, we
shall again be disappointed. All reports agree that the development of
the image on the screen depends on the child's interest in the picture
as a whole, and in its details. Exciting details come out sharply, while
adjacent parts may remain blank, blurred, or even appear in complementary
colours. Pictures which have no meaning for the child do not appear
on the screen. [27] The objects in the image can be moved about, and
their colour and size can be changed at will, or in response to verbal
suggestions. Synaesthetic phenomena also enter: if the subject's arms
are pulled while he is inspecting a horizontal line, the eidetic image
of the line will be lengthened; images of the Mueller-Lyer illusion may
be lengthened 'by as much as two yards'. [28]
Image and Meaning
A further step upward in the hierarchy leads to what I have called the
'picture-strip' kind of memory with emotive significance; and lastly
we arrive at the phenomena referred to as 'memory images' in ordinary
parlance.
An image is defined in
Drever's Dictionary
as 'a revived sense
experience, in the absence of the sensory stimulation'. But since
most of the sensory stimulation has been irretrievably lost in the
filtering-processes of memory formation, only some exceptionally sharp,
vivid details are perhaps capable of being 'revived' or 'reproduced';
the remainder of the experience must be 'reconstructed'. It has been known
for a long time that introspective reports on 'visual memory images' are
largely based on self-deception. Visual recall -- as Semon once wrote
-- 'renders only the strongest lights and shadows'; [29] but strictly
speaking, even shadows are absent from visual images -- as they are from
Chinese paintings; and so are, as a rule, all but the crudest shades of
colour. The normal adult's memory-images are much vaguer, sketchier in
outline than he is wont to believe; in most cases when he believes that he
possesses a visual image of a thing, he is really referring to aggregates
of simplified perceptual schemata, held together by conceptual links.
This has been amply demonstrated (cf. Book One,
pp. 346
seq.) In the Binet-Mueller test [30]
the subject is directed to memorize a letter square (comprising sixteen
or twenty-five letters in random distribution) until he thinks that he
has formed a visual image of it, and can 'see' it in his mind's eye.
But when he is asked to read the letters in his image in backward order or
diagonally, he will take up to ten times longer than when reciting them
in their proper serial order from left to right.

 

 

Another classic test is the drawing of elephants by patients suffering
from a form of aphasia which impairs symbolic thought but leaves
perceptual faculties intact -- a test first used by Pierre Marie, and
later by Henry Head: [31]

 

Case No. 8 ('semantic' asphasia): Asked to draw an elephant, he moved
his pencil about aimlessly, saying 'I can't get the idea'. Then he
suddenly drew the outline of the head, back and belly, adding the four
legs and an eye; the tusks were indicated but he omitted the trunk. I
asked 'What is the characteristic of an elephant?' To this he replied,
'Its trunk; I see I have omitted to put in his trunk'.
Case No. 11 . . . made an incomplete drawing of an elephant to
order. Asked if he had left out anything, he replied 'His ear', and
made a mark on the side of the head. When I inquired 'Has an elephant
got anything else?', he answered 'Trunk, eye, tail, toes', marking in
each object in turn as he named it; but he forgot the tusks.
Case No. 21 (a woman of high intelligence with some semantic disorder):
When I requested her to draw an elephant she produced a picture
distinctly resembling this animal, except that she gave it a bushy
tail and forgot the tusks. After she had finished she exclaimed 'I
haven't put the tusks in. I can't remember where they come. They come
from just below the eye, I think; but I don't know. I believe they
are teeth and should come out of the top of the jaw really.'

 

The quotations show that the visual image of the elephant was not in
fact a 'perceptual whole' but a mélange of perceptual
and
conceptual entities; the glue which held the visual parts together was
meaning
. Thus in a number of drawings the tusks at first appeared
on top of the elephant's head as if they had been horns; and only when
their function was remembered were they put in their correct place.

 

 

We have now reached the boundary between the perceptual and symbolic
hierarchies -- the highest level of perceptual integration, where
symbolic coding must take over if further progress in learning is
to be achieved. The schematized visual forms of trunk, legs, tusks,
seem to be the upper limit of the patient's capability of forming true
perceptual Gestalt-traces. When it comes to reproducing the 'image'
of the complete elephant, the
visual pattern
of the tusk
is manipulated as a
symbolic unit
, labelled a 'tusk'. It is,
once more, a double-faced entity: one side is a complex and flexible
perceptual whole, the other is a semantic unit which signals the word
'tusk' and is activated by the same signal.

 

 

 

Klangbild and Wortschatz

 

 

A similar frontier is found in audition, where perception of sound
patterns turns into interpretation of language. Here one face of the
entities which pass the frontier is a
Klangbild
, the other belongs
to the
Wortschatz
-- a distinction between 'sound-picture' and
'word-treasure' (i.e. vocabulary) -- which Wernicke made in 1874. [32]
There is considerable doubt whether the discrete elements or 'segments'
of speech are phonemes, syllables, or even larger units. Let us assume
for argument's sake that the segments are characteristic vowel-consonant
combinations -- digrams or trigrams* and call these the
perceptual
units
(the 'sound-pictures' of speech). In whatever way you
define your unit, when it comes to the transition from perceiving the
sound-picture to interpreting its
speech-value
, a considerable
degree of ambiguity creeps in. Thus the speech-value of a vowel (the
o-ness of an o) is independent of the frequency of its fundamental, and
depends on the characteristic frequency-ranges of its two formants (its
dominant partials). But these formant-ranges overlap; and accordingly
'a sound with a particular spectrum will be recognized as /î/
on one occasion and /ê/ on another'. [33] Most consonants,
on the other hand, vary their pitch according to the vowel with
which they are associated, and are characterized not only by pitch
but also by the change, and rate of change of pitch. [34] Thus the
identification of language units depends to a considerable extent on
their meaning-context; experimental subjects confuse m and n in nonsense
syllables more frequently than when listening to meaningful speech;
and the ambiguity of the input can only be resolved with reference
to the preceding and following inputs in the psychological present. In
discussing the practical feasibility of robots for translating speech into
typescript, Fry and Denes concluded: 'It is unlikely that the mechanical
speech-recognizer will be successful without the use of some form of
linguistic information.' [35] It is the same as with ambiguous visual
stimuli, whether they are riddles of the face-hidden-in-the-tree kind,
or Frauenhofer-lines in the spectroscope. 'Es hört doch jeder nur
was er versteht', Goethe noted in his
Maximen
.
If scanning is an aid to vision, articulation is an aid to hearing. When
we try to remember a tune, we hum it. The decisive factor in the
emergence of human speech was not the development of the ear, but
of the vocal organs and of the speech area in the motor cortex. The
multiple feedbacks of auditory-vocal co-ordination exceed even those of
oculo-motor co-operation. The child learns words by articulating them;
adults learning a foreign language follow a similar procedure. Reading is
more often accompanied by sub-vocal articulation than by images in the ear
(except if you know intimately the author of what you are reading). The
analysis of speech-sounds by matching them against innervation-patterns of
the vocal tracts is a much simpler procedure than the acoustic analysis
of the ambiguous sound spectra. However complex and variable the wave
form of a vowel which reaches the ear, its identity as a language unit
depends on its two formants, which in turn depend only on the resonance
effects produced by the alterations of shape of two vocal cavities, mouth
and pharynx. Paget [36] proposed that 'in recognizing speech sounds the
human ear is . . . listening . . . to indications, due to resonance, of
the position and gestures of the organs of articulation'. More recently
a team of American experimentalists in the Haskins Laboratories have
come to the same conclusion that 'speech is perceived by reference to
articulation -- that is, that the articulatory movements and their sensory
[proprioceptive] effects mediate between the acoustic stimulus and the
event we call perception'. [37] Lastly, Lawrence (1959) has described a
method of speech-analysis which specifies such details as the frequencies
of resonance of the vocal tract and the vibration frequencies of the
vocal chords -- a method of analysis 'which preserves all perceptually
valuable features, but is vastly simpler than the acoustic wave form. From
an information theory point of view it is a tremendous reduction in the
bit rate -- it is a reduction of the order of thirty to one. It may well
be that speech is held in the short-term memory in a form like this.' [38]
Once again we find confirmed that perception is 'something the organism
does, not something which happens to the organism' [39]; that responses
enter at every level of the hierarchy into the processing of stimuli;
and that motor activities intervene to analyse the input long before
it has achieved its full status as a 'stimulus' -- before it has, for
instance, become a meaningful word capable of stimulating the central
process which is to mediate the 'response'. As Drever, Jr., has so
nicely put it: 'Associationist learning theory, where it has tried
to hold to a strict S --> R pattern, appears to be lapsing into an
esoteric scholasticism. Where it has abandoned S --> R in favour of
S --> X --> R, there are complaints that it is struggling to say
things which must be said, but doing so in a language which is no longer
appropriate. [40]
Perceptual and Conceptual Abstraction
One last example of a frontier where perceptual organization can do no
more for you, and symbolic thought has to take over.