PERCEPTION AND IDEA
If we cross the fingers, a single object beneath them appears to be
two; and yet we do not say that there are two, for sight is more
decisive than touch; but if touch were our only sense, our judgment
would declare that the single object is two.—ARISTOTLE
§ 24. =The Problem in General.=—The chapters on the mental
elements—sensation, simple image, feeling—have made you acquainted
with the _results_ of psychological analysis; it was only occasionally
that you were asked to analyse for yourself. Henceforth we shall be
dealing with experiences that offer themselves _for_ analysis; with
experiences that, however simple they may at first sight appear, turn
out on investigation to be complex. We shall thus be following the
example of those men who, long centuries ago, tried to bring order
into mental phenomena and to establish a science of mind. We have an
enormous advantage; for they were working in the dark, and we are
working in the light of their discoveries. Still, our procedure will
be the same as theirs; and the change of work brings with it certain
difficulties that you must realise at the outset and be ready to face.
Well begun is half done.
First of all, then, your reading henceforth will be more difficult,
because you will have to _keep more things in mind_. The analysis even
of so comparatively simple a thing as a perception or idea cannot be
performed in one breath. A knot in a rope may be beautifully simple,
and yet you may spend a week in learning it! Secondly, the examples
chosen by the author may not be just the right _examples_ for you;
even perceptions and ideas, again, differ a good deal in different
minds; and an example that is illuminating to one reader may leave
another quite blind. So you must look for your own examples in your
own experience. Thirdly, you have now to wrestle with the problem of
_meaning_ (p. 26); for all perceptions and ideas, and all our still
more complicated experiences, mean something; a perception is always
the perception _of_ a tree or a wedding or what not; and an idea too is
always the idea _of_ something, whether of the landing of Columbus or
of the quarrels of the gods in Homer. You must get clear, then, about
the psychology of meaning. Fourthly, these concrete experiences that
you are to analyse have a long _history_; and in seeking their nervous
correlates we shall be obliged, oftentimes, to go far back, even beyond
the individual, to the development of the race. In doing this we do not
change the problem of psychology (p. 18), but we enlarge our view of
it; a mere reference to the organ of sense or the present condition of
the nervous system is no longer enough.
All this means, in summary, that we are passing from the abstract to
the concrete, from the meaningless to the meaningful, from the simple
to the complex. We still keep to our scientific point of view, and
we still employ our scientific method. The change is not in us, who
are psychologising, but in our subject-matter; the plot begins to
thicken; and this growing complexity of subject-matter naturally makes
increasing demand upon our scientific resources.
§ 25. =The Analysis of Perception and Idea.=—Sensations and simple
images can hardly occur, by themselves alone, in our everyday
experience. The practised psychologist may be able to focalise a
sensation, to make it so vivid that it stands out almost as it would
under the experimental control of the laboratory; but his is an
exceptional case. The units of our daily experience are rather such
things as the sound of the piano in the next room, the sight of the
tree budding just outside the window, the memory of last winter’s
snow-piles, the forecast of to-night’s Pathetic Symphony; that is, they
are _perceptions_ and _ideas_. Notice that they come to us in the first
place as units, as wholes; they show no lines of natural cleavage;
they are unitary and self-contained. Yet they are not psychologically
simple; if they were, we should never have lit upon sensations and
simple images. _All perceptions and ideas may be analysed._
A typical =perception= _resolves, to begin with, into a number of
sensations_. The sound of the piano is, after all, the sound of certain
compound tones, played together and in succession; and the sight of
the tree is an arrangement of colours. The characteristic part of a
perception, then, the part that we may conveniently call its core or
nucleus, may thus be analysed into sensations. Only the core, however;
for _the sensations are supplemented, secondly, by various images_.
The sound comes to us as the sound of _the_ piano, the instrument
of that familiar look; and we may have an imaginal hint of the child
playing, of the score, of its special difficulties, of all sorts of
related things. The tree, too, is _that_ tree, the familiar cherry that
the caterpillars infest so badly, that grew so much last year, that
will presently cut off the view across the street, that very likely
will interfere with the beech. Remember that these are the author’s
instances, and that you must replace them by your own! The point is
that the complement of images is there; and you will notice that it is
not stable; it may be full or scant, and it may lead the mind this way
or that; but, whatever it be, it puts more into the perception than the
sensory stimuli can account for; we perceive more than we hear or see.
Yes, and we perceive more than is furnished us by sensations and
images. It is a fact (which you will better understand presently) that
_every perception is shaped and moulded by the action of nerve-forces
which show themselves neither in sensation nor in image_. The nervous
system, whether by racial heritage or by individual habit, meets its
impressions halfway, and throws them into certain customary forms. We
take both the tree and the piano to be real things, and we take them
to be things that occupy real space; we perceive them as objects of
the outside world, and we perceive them as solid or space-filling. We
do this because we have a natural and ingrained tendency to cast our
perceptions into the forms of ‘thing’ and ‘space’; and this tendency of
the nervous system does its work automatically; it has no correlate
of sensation or image; but it is none the less effective, so to say,
_behind_ the sensations and the images, in determining the perception.
You must just accept this statement now; it will become clearer later
on.
A typical =idea=, in the same way, _has a core or nucleus of images_.
Last winter’s snow may come to us in many different ways, because our
equipment of images is very variable (pp. 75 f.); it will come to most,
perhaps, as a visual picture, an uneven spread of white, with streaks
of grey-brown on the peaks and along the valleys, honeycombed and
broken from some partial thaw. To-night’s music will come, possibly,
as the sound of the opening adagio measures, or of some theme from
the allegro. Here again, however, the nucleus has its surroundings;
_other images cluster about it_; we recall the day so-and-so got his
feet wet, or the big fall of that December Thursday; we see our place
in the concert-hall, or hope that this time the tympani will be in
tune. _Nor is the idea altogether a matter of images._ We can hardly
think of those opening measures without kinæsthetic sensations from the
throat, or from some muscular beat of the rhythm; we can hardly think
of getting our feet wet, or of seating ourselves in the hall, without
some actual movement that arouses sensation. Find your own instances,
once more, and do not trust the author! You will find that _the typical
idea is thus in part sensation, just as the typical perception is in
part image_. Finally, the idea, too, is subject to the pressure of
the _directive nerve-forces_; it takes the same customary forms as
the perception. Columbus is thought of as a real person, acting in a
real world of space and time; and Zeus as an imaginary person in an
imaginary world; but there is no difference in the form of the ideas,
and no difference of form between these ideas and the perception of the
stranger who has just passed the window.
So we have _the characteristic nucleus; the varying complement; and the
brain-habit behind all_. And if we can analyse the perception or idea,
nucleus and surroundings both, into its mental elements; if we can say
what nervous processes are correlated with these elementary mental
processes; and if we can further establish the nature of the guiding
and shaping nerve-forces; then our psychological account will be, in
strictness, complete. Yet we shall have passed over something that,
as we have ourselves admitted, is in everyday life most strikingly
characteristic of these experiences; the fact, namely, that they
=mean=; that our perception of the tree means the tree, is a perception
_of_ that tree, and our idea of snow means the snow, is an idea _of_
that snow. _What, then, from the psychological point of view, is this
meaning?_
§ 26. =Meaning in Perception and Idea.=—We learned in § 6 that mental
processes are not intrinsically meaningful, that meaning is not a
constituent part of their nature. We have seen, indeed, that the whole
notion of meaning is really foreign to science. When we ask, then, what
meaning is, from the psychological point of view, are we not asking an
irrelevant and unscientific question?
Not necessarily. A science cannot free itself, offhand, from its own
history; and, historically, psychology has been much concerned with
meaning. Moreover, meaning is of very great practical importance; we
communicate meanings, we apprehend meanings, we act upon meanings; and
although science is not bound to treat only of what is practically
important, yet it can hardly neglect a matter of great practical
importance that comes its way. Our question, if we rephrase it a
little, merely asks _that a term, familiar to us in our daily life,
be translated into the language of science_; and if the translation
out of common sense into science is to be made at all, psychology is
the science in which the equivalent of meaning will be found. For
these reasons we are justified in discussing the matter here; and the
question at issue—let us be quite clear about it—is this: What mental
processes, in perception and idea, are the scientific equivalent of
what we know in everyday life as meaning? _what processes carry the
meaning?_
The answer is that the processes which surround the nucleus carry the
meaning. _Psychologically regarded, meaning is always context_; and
the context is the fringe of related processes that gathers about the
central group of sensations or images. Ordinarily, as our analysis has
shown, the two come together; but they may be disjoined. When the word
‘house’ becomes meaningless with repetition (p. 26), it is because the
bare sound grows more and more vivid and dominant; like the nestling
cuckoo, it drives out its normal associates; and these associates,
the carriers of its meaning, sink lower and lower into the obscurity
of the background. So the meaning, almost literally, drops off, falls
away. When one and the same experience has different meanings, it is
because the context varies; we read, for instance, that so-and-so
received a warm welcome, and we put directly opposite interpretations
on the words, according as so-and-so was friend or enemy. When we
mistake a meaning, it is because we supply a context of our own: what
child, reading that “the quality of mercy is not strain’d,” has not
thought of mercy being wrung out through a strainer, as the cook wrings
the water out of cottage-cheese in a muslin bag? The context of images
is obvious; the rain falls freely, like water poured through a sieve;
but what is _strained_ comes out grudgingly in drops. When one and
the same meaning attaches to several experiences, it is because these
different experiences are received into the same context, or into a
context so nearly the same that for practical purposes the differences
disappear; for example, the experiences may be named, that is, may
be received into a context of verbal ideas; and verbal ideas tend to
become stereotyped, as it were, into permanent groups. All the facts of
§ 6 are to be accounted for in this way, by the distinction of nucleus
and context.
_Originally, we must suppose, meaning was carried exclusively by
kinæsthetic and organic sensations._ Think of the animal that we
pictured on p. 101 as startled by some sudden stimulus and as facing
the stimulus by way of a bodily attitude; the sensation is hemmed in,
like a jewel in its setting, by the sensations of organic stir and
motor posture; and these sensations give the meaning; they cry out
‘Danger!’; they are the psychological equivalent, the carriers, of that
meaning; without them the sensation would be meaningless. _Meaning is
thus older than the free image_; and kinæsthesis is still, for many of
us, the characteristic context, the common denominator of our meanings;
we hinted at this rôle on p. 47. None the less, the development of
free images, the images of memory and imagination, changes the whole
situation; kinæsthesis now has many rivals; and it depends on our
individual equipment of images, on our ‘type of mind,’ whether a
meaning shall be carried by a quiver of the stomach or some muscular
set, or whether it shall be carried by some complex of images. If we
were to work out a great number of cases, we should probably find that
_any sensory or imaginal process whatsoever is able, in our adult human
experience, to carry the meaning of any other_.
There is yet a further stage: a stage in which _meaning is carried
not by any sort of sensation or image, but simply and solely by
physiological processes_, by some set or disposition of the brain.
When the practised reader skims a number of pages in quick succession;
when the musician renders a composition in the prescribed key; when
an accomplished linguist shifts from one language to another as he
turns to his right or left hand neighbour at a dinner table; in cases
of this kind there need be no discoverable context; the stimuli press
the button, and the brain, prepared by constant practice in the past,
now does the rest. The experiences _mean_, positively enough; the
‘sense’ of the pages is grasped, as the eye hurries over the lines;
the three flats on the staff set the player’s hand and eye for the key
of E♭; the question put in French is suitably answered in the same
language; everything takes place _as if_ there were a fringe of images
that gave meaning to the bare perceptions; and yet imaginal fringe
and kinæsthetic setting may be conspicuous only by their absence.
Of course, there _has been_ context; one does not learn French and
German, or transpose on the piano, by gift of a ready-made nervous
system; even after years of work one may be a little uncertain of the
German auxiliaries, or have a repugnance to four sharps. The point is,
however, that an habitual and often-repeated context does, presently,
lapse altogether; the nucleus is not always supplemented; the nervous
system can now do, by a set or disposition that has no mental
correlate, what it used to do by processes that had as accompaniment
the sensations or images of the context.
It is plain, therefore, that _perception and idea are not always
so rich and complicated as we have described them_; we spoke, for
that very reason, of the ‘typical’ perception and idea. They range,
according to their age and use, from the cluster of nuclear processes
surrounded by a group of contextual associates, all under the guidance
of a directive nerve-force, down to a mere rag and tag of sensory or
imaginal process, wholly bare of associates, and dependent for its
meaning upon some habitual nervous set.
§ 27. =The Types of Perception.=—Our perceptions are based upon
three of the attributes or aspects of sensation: upon quality, upon
duration, and upon extension (p. 66).
The =quality= of sensation has already been discussed. We may take,
as instances of qualitative perception, the taste of coffee, the
resistance of a jammed door, and the note of a musical instrument. The
_taste of coffee_ analyses into sensations of bitter, the real taste
of the coffee-berry; of warmth; of pressure, the feel of the liquid
in the mouth; and of a peculiar fragrance, the odour of coffee. Along
with these goes a colour, the clear or clouded brown of the coffee
in the cup, and various other contextual processes. The _resistance_
analyses into the qualities of pressure from the skin; of strain from
the tendons of the arm; and of pressure, or something akin to pressure,
from the binding of the joints and the contraction of the muscles.
There is probably some organic stir; there is the sight of the door;
and there may be a further context. The _musical note_ analyses into
fundamental tone and overtones, and into the noise characteristic of
the instrument; the thud of the piano, the scrape of the violin, the
pluck of the harp. The supplement is perhaps visual; but here, as in
the other cases, verbal ideas may enter into the context; we may think
‘Violin, of course,’ All our qualitative perceptions are of this kind;
they come to us as meaningful wholes, and they may be analysed into a
number of sensory qualities, run or fused or blended together, and set
in various contexts of associated processes.
The attribute of =duration= has not yet been defined. It is the bare
going on, going forward, keeping like itself, that may be observed in
any and every sensation; you recognise it most easily, perhaps, if you
listen to a tone, or attend to the kinæsthetic complex as you slowly
extend your arm from the elbow. It is _the elementary time-factor
in all our perceptions of time_,—in the perceptions of period, of
interval, of rate, of rhythm, and so on; though in some of these
perceptions it is overlaid and obscured by other factors. Qualitative
perceptions undergo relatively little change, just because they are
qualitative perceptions; the best and easiest way to _mean_ a quality
is to _be_ it; the best way to mean the coffee-taste is to be the
coffee-taste; and so our perception of that taste remains practically
the same all our life long. Time-perceptions, on the other hand,—and
the same thing is true of space-perceptions,—change enormously; the
nervous system finds all manner of short-cuts to the meaning of time;
and these short-cuts have to be _un_practised, to be practised out,
if we are to observe the perception in its original form. Thus, to
take the simplest case, a period of time may seem long because the
kinæsthetic strain of waiting becomes intense, or because a great
number of perceptions and ideas occur during its course; the strain and
the number of ideas have come to _mean_ length of time, and the primary
experience of duration, so to say, drops out of sight. If, therefore,
we wish our observers in the laboratory to compare periods of time; if
we wish to find out accurately what durations can be grasped by the
attention and held in the memory; then we must break them of these
time-habits, and must somehow train them to disregard strain and to
discard imagery. We cannot often carry the unravelling of a perception
to the very end, though we can go some distance behind the appearances
of everyday life.
The attribute of =extension= is the bare character of patch or spread
that inheres in all sensations from eye and skin, and possibly also in
kinæsthetic and organic sensations. No point of light or pressure is so
fine that it is not areal. Extension is _the elementary space-factor
in all our perceptions of space_. It enters most obviously into the
perception of surface, as duration enters most obviously into that of
period; but it is the basis also of our perceptions of form, size,
distance, locality, direction. Like duration, it is often obscured and
overlaid by other factors.
Here, however, you will raise an objection. Have we not said, on p.
115, that perception is shaped and moulded by nerve-forces that have
no mental correlates? and did we not take as an example the casting of
perceptions into the forms of ‘thing’ and ‘space’? How, then, can we
now speak of perceptions _of_ space?—Well, for one thing, there are
various kinds of spatial perception; and it will not do to assume that
they are all alike a matter of brain-habit, without mental correlate.
Secondly, however, there is a difference between perceiving the piano
or the tree _as_ spatial, and turning our attention directly upon its
spatial characters, its size or form, its distance or direction. In the
latter case, we may rightly speak of a perception of space; we may so
speak, even if the various kinds of spatial perception do turn out to
be matters of brain-habit; and we must examine every kind for itself,
precisely in order to determine how far it is sensory and imaginal,
and how far it is a form impressed on sensations and images by the
trend of the processes in the brain.
So the objection is answered. Coming back to the subject, we note
that some of our more =complex perceptions= have a twofold basis:
thus the perception of melody is at once qualitative and temporal,
and the perception of movement is at once temporal and spatial. Nay
more, the perception of a scene, a situation, an event, is threefold:
qualitative, temporal and spatial; think of a scene of grand opera, or
of an accident on the street. In general, the analysis of these complex
perceptions follows from that of the simpler modes, though every one of
them has its own psychological problem.
It may seem strange that we have not distinguished a group of
perceptions based upon sensory =intensity=. The fact is, however, that
while intensity enters into all sorts of perceptions (lemonade must
not be too sour, the members of a rhythm must be variously accented, a
distant sound is faint), it only rarely characterises a perception; and
when it does, the perception thus characterised belongs to one or other
of the groups already mentioned. We say ‘What a heavy child!’—but the
perception of weight, like that of resistance, is itself qualitative.
Or we say of a certain composer ‘He always overdoes the drums!’—but
the drum-rhythm is itself a temporal perception. _We cannot point,
then, to a separate class of intensive perceptions._
§ 28. =The Perception of Distance.=—A complete psychology of
perception would contain an analytical treatment, up to the limits of
our present knowledge, of all the various perceptions, qualitative,
temporal and spatial, as well as complex, that occur in experience.
Such a treatment is here out of the question. We must pick and
choose; and as a sample of perception at large we shall consider the
_perception of distance_. We seem, quite immediately and directly, to
_see_ distances; we see that our friend is coming nearer, we see that
he has passed the bridge, we see that he is entering the gate, we see
when to shake hands with him. Yet there is no sensation of distance,
and there is no specific stimulus to distance. What, then, really
happens?
In the first place, there are plenty of =visual cues= to distance. We
take familiar things to be far off if they look small, and near by if
they look large; the size of the men and vehicles in the street makes
us realise the height of the building we are gazing down from. We take
things to be far off, again, if they are hazy and bluish, near by if
they are clearly outlined and varied in colour; everyone knows or has
read of the deceptive nearness of distant mountains in clear dry air.
We notice the distribution of light and shade; a morning or evening
landscape, a shaded face or sphere, looks deeper, more solid, more
plastic, than the landscape at high noon or the outline drawing. We
notice the course of boundary lines and the visibility of surfaces;
that is nearer which cuts across the rest or blots part of it out;
the telephone wire is thus nearer than the elm, and the elm is nearer
than the house. We notice the number of objects that the eye must
traverse to arrive at its goal; and the more numerous the objects, the
farther off do we take the goal to be; the town looks near, we say,
but there are all those fields, and the wood, and the churchyard, and
half-a-dozen farmhouses to pass, and then the outlying houses; it must
be a good two miles. We get various hints from movement; a crawling
train or car is far away; and if we are looking at a near object and
move the head to one side, distant objects move in the same direction,
while if we are looking at a far object and move the head, near objects
go in the opposite direction; and so on. _All these things—linear
perspective, aerial perspective, chiaroscuro, interposition, number,
movement—are, however, secondary affairs_; they represent short-cuts
to the meaning of distance (p. 123); they do not lead us to the
perception of distance itself. At the same time, we should bear in mind
that these secondary processes were there, ready to take up the burden
of meaning, all the while that the perception was forming.
Having thus cleared the ground, we naturally appeal to experiment; but
unfortunately the first step that we take lands us in difficulties.
It is found that, when all the cues above mentioned are ruled out,
the estimation of distance is still possible; and many psychologists
believe that it depends upon =kinæsthetic sensations= set up in and
about the eye. Each eyeball is slung in its orbit upon six muscles; and
the contraction of these muscles is, naturally, greater for convergence
of the eyes upon near objects than for their convergence upon far; so
that the _sensations of convergence_ seem fitted to play a part in
the perception of distance. If only one eye is used, these sensations
may be replaced by others, derived from the muscular system, within
the eyeball, that adjusts or accommodates the lens for clear vision
at different objective distances. The _sensations of accommodation_,
though, in ordinary binocular vision they are entirely subordinate to
the sensations of convergence, can nevertheless—within a lesser range
of distances—play the same part in perception. Unfortunately, as was
hinted just now, the results of these experiments are disputed; we
shall come back to them, and to the possible rôle of the kinæsthetic
sensations, later on.
Meantime, what is to be said of the =eyes= themselves, and of the
impression that a solid object, a tridimensional stimulus, makes upon
them? If you hold up a closed book, back towards you, in the middle
line of the face, and if you observe it alternately with the right and
left eye, you will find that the two views do not tally; the left eye
sees the back and the cover to the left, the right eye sees the back
and the cover to the right. If you now make outline drawings of the
two views, mount them upon a suitable card, and look at them through
a =stereoscope=,—which, as you know, combines them into a single
view,—lo! you have before you a solid book, the back near you, and the
edges away in space. _It is as if the two eyes had reconciled their
conflicting views, and the result were depth or solidity._
But is not this the very thing we were in search of? have we not at
last got at the secret of visible depth? No; we are rather _at the
crucial point of our discussion_. For this binocular picture, the image
seen in the stereoscope, cannot be, of its own nature and in its own
right, deep or solid, unless there is a depth-sensation; and that
conclusion goes against everything that we know both of sensation and
of the stimuli that arouse sensation. To avoid it, some psychologists
call in the kinæsthetic sensations from the muscles of the eye. _Depth
or distance, they say, is psychologically a blend or fusion of visual
and kinæsthetic sensations._ Our binocular view of the book, its
appearance to the two eyes, is in itself flat; but we run the eyes
over it, and the muscular sensations thus blend with the visual. Nay
more, even if we hold our eyes fixed, there is still a _tendency_ to
move them; and this tendency, now ingrained in our nervous system, is
enough to realise the perception. Indeed, if experiment fails in every
case to show the sensations of convergence and accommodation, that is
just because the fusion is so long-established and so ingrained; we
perceive distance, the fusion itself; we can hardly expect to recover
the kinæsthetic sensations that originally entered into it; the wonder
rather is that they should ever appear, that experiment should be able
to reveal them at all.
No one can say positively that this hypothesis is wrong; but it
is difficult to believe that the blend of visual and kinæsthetic
sensations should yield a result so different from either,—namely,
the perception of space. It seems safer to say that _the binocular
picture_, the appearance of the book to the two eyes or the combined
image of the stereoscope, _carries the immediate meaning of depth or
voluminousness_. The picture is not itself deep or solid; but we cannot
help perceiving it _as_ deep and solid; and this pressure is laid upon
us by what we have called racial heritage, an inherited disposition
of the nervous system: _the brain meets the impression halfway_. The
binocular picture thus becomes the core or nucleus of the perception;
and the meaning of depth is carried by a nervous disposition that
has no correlate in sensation or image. The kinæsthetic sensations
may then very well serve, as a secondary context, to give precision
and accuracy to the perception, to develop the perception of crude
voluminousness into the perception of definite distances. As to the
nervous disposition, we can only say that it has been set up by the
same biological causes that have made the organism a motor organism,
one that moves freely in space; beyond that general statement we cannot
go.
So far we have dealt with the space of sight; but there is also a
=space of touch=; and we have next to ask _whether the perception of
distance can be couched in terms of touch alone_. Our appeal lies to
those who are born blind. Observations show that, in their case, the
direct perception of solidity, of plasticity, is rare and fleeting;
it arises, perhaps, when they clasp a child to their breast, or when
they have been trained by long manipulation to distinguish objects of
various shapes and sizes; it does not form a permanent item of their
mental furniture. The blind _behave as if_ they perceived distance;
they avoid obstacles,—near obstacles by the pressure or temperature of
the air reflected back upon their face, and remote obstacles by sounds;
they can be taught geometry, and they measure objective distances by
pacing; but the meaning of distance seems always to remain abstract,
very much as the meaning of light and colour must remain abstract;
there is no realising perception of distance. The brain mechanism which
is ready to act at once at the behest of sight thus seems to be lacking
where touch alone is present; even the perception of crude volume, of
depth, has to be built up afresh by the individual. _The blind live
mainly in a world of sounds_; touch is employed, as a rule, only for
special and limited purposes, such as dressing, reading, handicraft;
and their world is therefore not pervasively spatial, like the world of
the seeing.
Go back now, for a moment, to the objection raised on p. 124! We have,
as a matter of fact, been led to the belief that =the meaning of depth
is carried, in the last resort, by a brain-habit=. But how differently
does this sentence read before and after the discussion! You have
learned something of the difficulties of the study of perception;
you see why it is necessary to look at perception historically,
developmentally; you have been taken behind the obvious visual cues to
the perception itself; you have seen how the kinæsthetic sensations and
the binocular picture may be made the subject of experiment. Even the
bare outline that the narrow compass of the present book allows should
convince you that the objection was duly answered.
§ 29. =The Problem in Detail.=—Every one of our familiar perceptions
might, now, be treated in this same fashion, and in indefinitely
greater detail. We should start out with our pattern of sensory
nucleus, imaginal context, and brain-habit; and we should push our
analysis back and back, in the effort to reach the primary and
ultimate form of the perception we were discussing. The quest is
fascinating; for these are old, old bits of the mental life; to trace
them home would be to go back to the Stone Age—or further; the
earliest men we know of perceived the things that we perceive. Whether
psychology will ever reach the final goal cannot be said; but at any
rate the problems are genuine problems; they can be resolved only by
intensive and long-continued work; and they demand an extraordinary
ingenuity in the devising of experimental controls and an unusual
degree of patience in experimenting. Men spend their lives among dead
languages and buried cities; why not excavate and explore the inner
world of perception?
Let us take an instance or two. Consider, first, the perception
of =movement by the eye=. Many psychologists assume outright a
special sensation of movement, something that we might call a
_travel-sensation_. That hypothesis cuts the difficulty; but the
sensation is no more admissible than the depth-sensation, and for like
reasons. Other psychologists call attention, in a more scientific
spirit, to the fact that in all cases of sudden change there is a
_sensory index_ of that change. If, for instance, a tone is quickly
changed to a higher tone, or a light suddenly reduced to a duller
light, there is a moment of sensory blur or confusion, a moment in
which the quality or intensity ceases to be clear and distinct; so
that, if you were called upon to identify it, you could say only
‘It lies somewhere about such-and-such a part of the scale.’ _This
blur is the sensory index of change_; not a new sensation, but a
modification of existing sensation. We have it in the perception of
visual movement; there is a blur of positions; and it may reasonably be
referred to the positive after-image. A shooting-star flashes across
the sky; it leaves a trail of after-image as it moves; you see it both
at the place it started from, and at the place where it disappears, all
in the same present time; thinking of it, nevertheless, as a star, a
point of light like other stars, you perceive movement. The same thing
holds for the perception of rapid movement on the skin.
So far everything is in order. Now, however, let us make a simple
experiment. You know the =stroboscope= or zoetrope that is sold in
the toy-shops: a cardboard drum, open at the top, that twirls on a
handle; a strip of paper, on which are printed phases of some movement
(the flight of a bird, the gallop of a horse), is placed inside, round
the bottom of the drum; and you look down at the strip, while the
instrument revolves, through vertical slits cut at regular intervals in
the upper half of the drum-wall; you then see a continuous movement.
Suppose that you make a new strip, on which you draw simply two lines,
a vertical and a horizontal; you draw them some distance apart, but in
such wise that, if they came together, they would form a right-angle.
Turn the drum slowly, and you see the two lines; turn it swiftly, and
you see the right-angle, like a letter L; turn it at a middle rate, and
you see—according to the direction of turn—the vertical _fall over
into_ the horizontal, or the horizontal _rise up into_ the vertical.
You see movement, where there is no movement to see! Here, then, is a
case of _perception of movement in terms of sheer brain-habit_, of
a settled nervous disposition that now has no mental correlate, but
whose establishment has depended on the past history of the individual,
possibly of the race.
Take, as a second instance, the perception of =melody=. Primitive
melodies seem to be of two types. In the one, the scale arises
by synthesis of small tone-steps or tone-distances, which are
approximately ‘whole tones’; the melody consists only of two or
three of these steps, and the last and lowest tone is the principal
note of the tune. In the other, the scale arises by analysis of the
larger consonant intervals, fourth and fifth; these intervals are
broken up into smaller steps; the octave appears as a drone-bass;
the first and highest tone is the principal note. An intermediate
type keeps for the most part to small steps, but shows ascents and
descents _portamento_ through octave, fifth and fourth; it, too,
makes the first and highest tone the principal note. We can account
for a good deal of this development: we know that the voice cannot be
evenly sustained in recitative, but naturally drops; we have reason
to believe that the memory of absolute pitch is strongly developed
in primitive peoples (parrots repeat their tunes at the same pitch,
and the same thing is largely true of young children); we know the
recurrent tonality of the octave (p. 52); we know that the fourth is
the natural drop of the voice at the end of a sentence, and the fifth
its natural rise in asking a question; we know that men, women and
boys, singing in ‘unison,’ will really sing in octaves, and often in
fifths and fourths; we know that the semitone, the final unit of our
own scales, is the smallest tone-step that can be accurately sung;
we know that musical instruments were invented very early, and that
they must have helped to give stability to the vocal scale. These
things, however, are not enough. For behind all music lies what we must
call an =intent to express=, as behind all speech lies an intent to
communicate; and this intent baffles us; we can only say, once again,
that it is carried by some native and ingrained disposition of the
nervous system. The possibility of music is further bound up with the
possibility of =transposition=; the melody must be reproducible and
recognisable, whatever note it start from; and primitive melodies do in
fact begin on different notes, and yet keep the same form. It may be
that the primitive singer felt his tones, felt the adjustment of his
larynx, more keenly than we do. Movements of the larynx are muscular
contractions, and their sensations are subject to Weber’s law (p. 68);
so that, whether the vocal cords are slack or tense, their tension
must be increased _in the same proportion_ to get equal differences in
muscular sensation. Here is a possible organic basis for the relative
constancy of the tones within a melody; the difficulty is that even
primitive melodies seem to be shaped, not by feel, but by ear.
We may take, as a third instance, a group of perceptions that have
been named =optical illusions=. In a certain sense, most of our
space-perceptions are illusory. Distance, for example, soon closes up
on itself; if we try to stop, halfway, a friend who is walking down a
long corridor, we shall be likely to call out before he has gone more
than a third of its length. Size is illusory; the size of the moon in
the sky is that of a pea held at arm’s length before the eyes. Form
is illusory: how often do we see a table square? Only direction is
adequately perceived. Yet we do not, somehow, think of all these things
as illusions; we are used to them, and can make allowance for them.
There are, on the other hand, certain simple arrangements of dots and
lines that yield, in perception, a result markedly different from that
which measurement would lead us to expect. These figures have, in
recent years, been made the subject of detailed study; that which is
here shown has, in particular, been repeatedly discussed and variously
explained. The simplicity of the forms is, indeed, treacherous and
misleading; analysis is very difficult; and there is no present
prospect that investigators will agree.
[Illustration]
The two horizontal lines are equal in measurement; they are unequal to
the eye. Why? One suggestion is that _the eye moves freely along the
one, and hesitatingly and obstructedly along the other_; the obliques
tempt out, in the one case, and hem in, in the other. The suggestion
can be tested; for movements of the eyes can be recorded; and it turns
out to be correct. The eyes, in passing over a line, like the lines of
the figure or of a printed page, move by sweeps or jerks; they go so
far, halt, and start again. Experiment shows that movements along the
lower horizontal take a longer sweep, and oftentimes come to a halt
only when they have shot beyond the end-points of the line; whereas
movements along the upper horizontal are themselves shorter, and
frequently come to a halt before the extremities of the line have been
reached. Here, then, is a kinæsthetic context to carry the meanings
‘longer’ and ‘shorter.’ Is the analysis adequate? Not for every case;
the illusion is found to vary with _our general attitude toward the
figures_. If we take them as wholes, the large open area below and the
closed diamond-shaped area above strike the attention; we say, from
total impression, that the lower horizontal is the longer. If, however,
we take the figures critically, part by part, limiting our attention
to the horizontals and disregarding the obliques, then the illusion
is greatly reduced and may, with practice, disappear. Here, then, is
a second context, which involves a brain-habit. Another suggestion is
that _linear perspective_ may be at work; the larger figure is a book
opening toward you, the smaller is a book opened away from you; the
lower horizontal is therefore further off, and should (if the two books
were of the same size) be smaller than the upper; since it is not,
the lower book is seen as the larger. There are, without doubt, many
figures in which perspective influences the perception; but there seems
to be no reason to invoke it here. A fourth suggestion is that we read
into the figures _ideas of our own muscular state_; the lower figure
has room to expand, it is stretching and yawning; the upper is cramped
and huddled; and so the illusion of length is produced. There is no
doubt, again, that this putting of oneself in place of the lines plays
a part in certain perceptions; but its influence here is negatived by
the swallow figure; the birds flying toward each other are further
apart than those flying from each other. On the whole, we may be
satisfied with the two contexts first mentioned; the discussion shows,
however, how many and how various motives may enter in to determine an
illusory perception.
[Illustration]
§ 30. =The Types of Idea.=—Idea takes its plan from perception; and
ideas may therefore be classified, like perceptions, as qualitative,
temporal and spatial. When, however, we speak of =types of idea=, we
usually have a different classification in view. Our ideas differ
as our equipment of imagery differs; some minds are rich in visual
or auditory images, others are poor or deficient. When first these
differences were brought to light, they seemed to be permanent and
clearly marked; children, especially, were classed _as eye-minded,
ear-minded, and touch-minded_ or motor-minded, according as their
ideas consisted predominantly of visual, auditory, or kinæsthetic
images; and it was thought no less necessary to discover a child’s
type, and to instruct him in accordance with it, than it is to test the
colour-vision of pilots and engineers. Moreover, since all ideas may
be translated into words, and since verbal ideas may also be visual,
auditory or motor,—ideas of the word seen, heard, or spoken,—three
sub-types were added to the main types of idea; _the verbal-visual, the
verbal-auditory, and the verbal-motor_. The doctrine of types found
support in pathology; thus, the famous French physician J. M. Charcot
reports a case of eye-mindedness in which visual ideas were suddenly
lost. The patient writes: “I possessed at one time a great faculty of
picturing to myself persons who interested me, colours and objects of
every kind; I made use of this faculty extensively in my studies. I
read anything I wanted to learn, and then shutting my eyes I saw again
quite clearly the letters with their every detail. All of a sudden this
internal vision absolutely disappeared. Now I cannot picture to myself
the features of my children or my wife, or any other object of my daily
surroundings. I dream simply of speech. I am obliged to _say_ things
which I wish to retain in my memory, whereas formerly it was sufficient
for me to photograph them in my eye.”
Nowadays the case could hardly be recorded in so simple a way; we
have learned that _ideational type is a very complicated and itself a
very variable matter_. Marked differences of imagery, as between one
mind and another, undoubtedly exist; but the distribution into types
is made difficult by two facts. The first is that there are great
differences in the nature of images even where the gross type is the
same; thus, of two predominantly eye-minded persons, the one may have
vivid and precise, the other vague and obscure images. The second is
that imagery varies with the nature of the test made, the situation
or material that arouses the images; in strictness, we can only say
that, under such-and-such conditions, the imaginal type proved to be
such-and-such. With these cautions before us, we can, however, make
out four common types. The =versatile= type uses visual, auditory and
verbal-motor images more or less indifferently. A second type prefers
=visual= images, with verbal-motor a good second. A third type prefers
=verbal images of the auditory-motor kind=, with visual images a poor
second. A fourth is almost exclusively =verbal-motor=. In this last
type, kinæsthesis, in the special form of the feel of articulation, has
reconquered the place that it held in the long-gone past, before speech
had come (p. 119).
We observe nothing of these differences in daily life, simply because
we are interested in meanings and not in processes; so long as the
audience gets somewhere near the meaning that the speaker or writer
is trying to convey, everything necessary for practical purposes has
been accomplished. All the same, _there are many signs of ideational
type_, if we are on the alert to seize them. The attitude of attention
is different, according as a man’s ideas are visual or auditory-motor;
the child’s mode of recitation is different, slow and systematic in the
former case, quick and impulsive in the latter; the mistakes made are
characteristic; and you can tell by an author’s style whether he has
visual images and whether he hears his sentences ring in the mind’s
ear. _It is natural to connect the dominance of certain images with
the choice of certain professions; but a correlation cannot be made
out._ “I should have thought,” remarks Galton, “that the faculty of
visualisation would be common among geometricians, but many of the
highest seem able somehow to get on without much of it;” and again “men
who declare themselves entirely deficient in the power of seeing mental
pictures can become painters” of acknowledged rank. The late Professor
James wrote to the same effect: “I am myself a good draughtsman, and
have a very lively interest in pictures, statues, architecture and
decoration. But I am an extremely poor visualiser.” These statements,
to be sure, were made without any thorough-going investigation; we
must remember that there are different ways of geometrising as there
are different styles and ideals of painting; and we may add that there
are plenty of instances on the other side; Goethe and Dickens were
magnificent visualisers. The study of imaginal type, in relation to the
interests and achievement of its possessor, thus offers an inviting
field of work.
Questions and Exercises
(1) State in your own words, and without looking at the book,
why the psychologist has to do with meaning, and what meaning is
psychologically. Illustrate from your own experience; find, in
particular, a case of meaning carried by kinæsthesis, and a case of
meaning carried in purely nervous terms.
(2) Draw diagrams to illustrate the typical perception and idea, and
the various stages in its reduction to the skeleton-type described at
the end of § 24.
(3) Qualitative perceptions undergo relatively little change. What
changes have they undergone? How is it that these changes have not
unfitted them to mean quality?
(4) A stereoscope and a set of slides prepared by the author may be
obtained from the C. H. Stoelting Co., 3047 Carroll Avenue, Chicago,
Ill. Explain the construction of the stereoscope, part by part; and
work carefully through the slides, writing down what you see. It is
useless to play with the instrument; take the experiments seriously.
(5) If you are touched with a pencil on wrist and chest, and try to
retouch the places stimulated, you are more nearly right on wrist than
on chest. Why? Try the experiment several times over.
(6) You have probably often heard the rising tone of a siren-whistle
sounded by some manufactory or given as a fire-signal. Can you image
it? If so, what is the index of change? If not, try to lay your finger
on this index when you next hear the whistle.
(7) If tastes and smells have not the attribute of extension, how do
you account for their apparent spread in space? If sounds are not
spatial, how is it that we can localise them?
(8) Is there such a thing as a purely visual rhythm? How would you
approach the question experimentally?
(9) Perform Aristotle’s experiment, by crossing the second over the
first finger of the right hand, and pressing on a marble placed under
the crossed joints, (_a_) Is Aristotle’s statement correct? Write out
your observations. (_b_) Is sight decisive? Helmholtz said, on the
contrary: “We are continually controlling and correcting the notions of
locality derived from the eye by the help of the sense of touch, and
always accept the impressions on the latter sense as decisive.” (_c_)
Can you work out the perception of a _thing_ or _object_, somewhat as
the book has worked out the perception of distance?
(10) Can you suggest methods for the determination of imaginal type?
(11) Close your eyes, (_a_) Let an experimenter draw a blunt-pointed
pencil _at an even rate_ along the inside of your arm from the shoulder
to the tip of the middle finger. The point seems to travel more quickly
at some places than at others: why? Draw a diagram of the arm, and mark
the places of apparent slowing and quickening. (_b_) Tie two pencils
together with a bit of rubber between, so that the points are 1-1/4 to
1-1/2 in. apart. Let an experimenter set the two points crosswise on
the skin at the shoulder, and draw them with even speed and pressure
along the inside of your arm to the finger-tips. The points seem to
converge and diverge: why? Draw a diagram as before.
(12) If a rough thread is drawn by an experimenter between your
forefinger and thumb, at first quickly and then slowly, it will seem
shorter in the first experiment than in the second. Why?
References
J. M. Charcot, Clinical Lectures on Diseases of the Nervous System,
iii., 1889, Lect. xiii.; W. James, Principles of Psychology, 1890,
i., chs. xiii., xv.; ii., chs. xviii., xix., xx.; C. H. H. Parry, The
Evolution of the Art of Music, 1896; article on Optical Illusions,
in Dictionary of Philosophy and Psychology, ii., 1902; W. Wundt,
Lectures on Human and Animal Psychology, 1896, Lect. xi.; Outlines of
Psychology, 1907, §§ 9, 10, 11; M. R. Fernald, The Diagnosis of Mental
Imagery, 1912; E. B. Titchener, Experimental Psychology, I., i. and
ii., 1901 (experiments on perception); Text-book of Psychology, 1910,
303 ff.