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constituting a speech, exhibit the wonderful per-
fection of this sense under these various aspects.^^

Sounds and Signs. — Sounds of all kinds are highly
susceptible of being conserved in the memory and
reproduced in imagination, and they are also readily
associated with other mental states. To this latter
property is due their aptness to constitute a system of
symbols. The repeated conjunction of the sound of a
name with the perception of its object causes the former
to suggest in the mind of the child the idea of the latter.
Later on, with the dawn of intellect and reflexion, words
come to be used and recognized as signs of things. In
acquiring a foreign language, the primary associations
are formed, not, as in learning our mother-tongue,
between the foreign words and the objects which they
signify, but between the former and the corresponding
terms in our own language, by the assistance of which
we ordinarily think and reason about the objects of

" A good musical ear is one that possesses a fine sensibility to
pitch, to melodious groupings of successive tones, and to symphonic
combinations of timbre. A good linguistic ear is one finely dis-
criminative of the quality of sounds, and of the varying degrees of
intensity which mark intonation or accent. As a consequence the
two aptitudes are not always united. The ear well formed to
catch the peculiar characteristics of the French, German, or Italian
languages, may be insensible to considerable differences in pitch, and
therefore unconscious of the discord effected by inharmonious com-
binations. Perfection in either line implies good individual capacity
of retention. Keen susceptibility to differences of pitch, and con-
sequently to musical harmony, may be found where the general
power of hearing is comparatively feeble, and vice versa. For a
good linguistic ear, however, general acuteness of the sense seems


experience. In commencing to read the connexion is
first formed between the visual sign and the oral
syllable or word, though gradually the intermediate
representation of the word tends to drop out of existence,
and in the end tlie written symbol immediately suggests
to us the object signified.^-

Cognitional importance of Hearing. — Notwithstanding
its very delicate sensibility as to differences in quality,
intensity, and duration, in addition to the very revivable
and associable character of its sensations, which all
conspire to give the ear such high intellectual value as
a representative faculty, it ranks very low as a direct
medium of objective knowledge. Of itself it affords no
information of the extension or impenetrability of
bodies — the two fundamental properties of matter.
Indeed, the attribute which it immediately reveals is
of purely secondary and accidental character. Never-
theless, of such a high order are the intrinsic excellences
of its sensations, and so admirably are they adapted
to compose a perfect system of signs, that, when once
a few elementar}^ experiences have been gathered by
the other senses, this faculty is enabled, by appro-
priating them, to put us into a position to take
possession of the rich treasures of knowledge acquired
by the whole human race.

Capacity for pleasure and pain. — The capacity of the ear
for pleasure is large, while its potentialities for pain are
comparatively limited. The agreeable feelings awakened
by the qualities of musical sound are of the noblest
and most refined character. They are rich in variety,
they do not pall by long continuance, and they may
be frequently renewed. In all these respects the}^
differ from the gratifications of the less refined senses.
A far greater part, however, of these higher pleasures
are traceable to intellectual and emotional enjoyment

^2 The muscular sensations excited in uttering words either
aloud or in a whisper, make a parallel line of association with the
aural and visual signs, and in persons in whom the faculty of
articulation is more retentive, or more frequently exercised in
acquisitions of this sort, thinking and reading in silence tend to be
accompanied by movements of the lips. Energetic eftort to realize
the full import of the visual sign occasions the same phenomenon.


afforded by the general character of a musical com-
position than to the mere sensuous satisfaction produced
by pleasant sound. Cultivation increases the refine-
ment and extends the range of this capacity for
happiness, but at the same time rendering the faculty
more keenly alive to defects and blemishes it anni-
hilates many minor pleasures possible to the less
delicate taste. Discord is painful to the musical
ear, and harsh sounds of any kind, as well as intense
noises, have an unpleasant effect on all normally
endowed persons.

Sight. — Physical and Physiological conditions. —
The formal object of the eye is coloured surface.
According to the now generally accepted undulatory
theory, the physical conditions of sight consist of
vibrations transmitted to the eye through the inter-
vening ether from the reflecting or self-luminous
body. Difference of colour depends on variation
in the rate of rapidity of the vibratory movements.
The organ of vision is an optical instrument of a
very complicated and ingenious construction. The
eye-ball is a nearly spherical body containing within
it three masses of transparent liquid or gelatinous
substances called humours, and so arranged as to
form a compound lens. The shape of the eye-ball
is secured by an outer coating called the sclerotic,
which embraces the whole eye with the exception
of the circular spot in front, where the transparent
cornea takes its place. Under the sclerotic is a
second covering, the dark choroid coat, and over the
interior surface of this towards the back of the eye
is distributed the retina. This is a transparent
network composed of several layers of fibres and
nerve cells, and connected with the choroid by a


layer of rods and cones. These latter seem to be
the properly sensitive apparatus. In the centre of
the retina is the yellow spot, which is the most
sensitive part of the organ, and here the rods and
cones are packed in greatest abundance. From the
retina slightly to the side of the yellow spot the
optic nerve proceeds to the brain. Rays falling on
it are unperceived, whence it is styled the blind spot.
Of the humours filling up the main body of the eye,
the middle one, called the crystaUine lens, which is
of double convex form, is the most important. The
shape of this lens is capable of alteration, being
rendered more or less convex by the automatic
contraction or extension of the ciliary muscle to
suit the distance of the object viewed. When
something is presented to the eye, the rays passing
from it enter the pupil of the eye and are con-
centrated by the lens arrangements so as to form
an inverted image on the retina. From the layer
of rods and cones forming the inner stratum of the
retina, this impression is conveyed as a neural
tremor to the brain, whereupon the sensation is

Sensations of Sight. — There are attached to the
eye both muscular and visual sensations proper.
The former, which measure the movement and the
greater or less convexity of the eye-ball, contribute
very much to the accurate determination of the
special relations of visible objects. The visual
sensations proper are those of light and of colour.
These are susceptible of very delicate shades of
difference, and the various hues of colour and


degrees in the intensity of light which can be
distinguished in a landscape are virtually innumer-
able. It has been estimated by means of some
ingenious experiments that an increase in the force
of a stimulus equivalent to about one in one hundred
can, within certain limits, be just discerned by the
eye. The principal species of colour generally
recognized are the seven hues of the spectrum, red,
orange, yellow, green, blue, indigo, and violet.
There are a large number of distinguishable inter-
mediate tints between these leading colours, and
the terms have therefore not a very exactly defined
meaning. These various hues are found to result
from the analysis of white light. The ether vibra-
tions which excite visual sensations are of enormous
rapidity, and the rate increases from about 460
billions per second, for red rays, to about 670
billions in the case of violet.

Helmholtz and others have traced analogies between the
colour spectrum and the musical scale. In point of agree-
ment we find {a) a series of seven principal colours, in corre-
spondence with the notes of the gamut, {b) both series
produced by variations in the rate of the vibratory stimulus,
and {c) both capable of certain agreeable and disagreeable
combinations described as harmonious and inharmonious.
The points of difference are however greater, {a) The
character of each of the tones of the musical octave is so
distinct and well marked as to have been recognized from the
earliest times ; the colours of the spectrum on the contrary
are vaguely defined and pass gradually into each other, many
intermediate hues having equally good claims to a recognition
in the scheme ; {b) the change in the musical octave advances
regularly in one direction, each succeeding note being farther
from the first, while in the spectrum the movement is along a
curve, and the last colour, violet, returns nearer than either
indigo or blue, to the earlier colours red and orange ; (c) the
auditory sensation rises regularly with equal increments in
the rate of vibration, whilst large changes produce no


conscious effect in parts of the spectrum ; (d) the range of
vision is exhausted by a single octave, while the ear can span
from six to eight.

Composite Sensations.— PAthough. the sensation of white
is evoked by a combination of physical stimuli separately
productive of other feelings, it is inaccurate, as we have
before indicated, to speak of the consciousness of white as
being a compound or complex mental state. The sensation,
in itself unanalyzable, must be accepted as such.^ The
true type of the compound or complex sensation is that
aroused by a union of different voices or instruments,
where attention enables us to discriminate the separate
elements of consciousness. The analysis of white light,
the existence of various forms of colour blindness, of
colour harmony, and of what are called iiegative^^
images, have suggested the hypothesis that the nerves
of vision distributed in the retina are of certain different
classes adapted to respond to particular elementary
forms of colour. The theory has assumed different
forms in the hands of different scientists, but as the
question is physiological rather than psychological, w^e
need not enter into it here.^*

Tone and Depth. — The term tone is sometimes used to
express the position of a colour in the spectrum, while
depth is dependent on the quantity of pure white light

'^'•' After-mages, incidental images, or spectra, are of two kinds,
positive and negative. The former term is used to denote the images
of sensuous perceptions of objects, which frequently continue to
persist for some brief time after the cessation of the stimulus. If
after gazing steadily for a few minutes at a coloured object we direct
our eyes to a white surface, instead of the positive after-image we
become conscious of an image of the object, but in the complementary
hue. This is termed a negative image, and is explained on the
above hypothesis as due to the temporary fatigue and consequent
obtuseness of the nerves previously excited, which are now unable
to absorb their share of the new stimulus.

^* The survival of these after-images was observed by Aristotle
and the Scholastics: "Si aliquis videt aliquid lucidum ut solem,
et subito claudat oculos, non advertendo visum, sed observando
illud directe, primo apparebit ei color rei splendidae deinde muta-
bitur in medics colores successive donee veniat ad nigrum, et
omnino evanescat et hoc non continget nisi propter simulacra
splendid! derelicti in visu." (St. Thomas, Comm. Dc Somuiis, lect. 2.)


blended with the colour in question. The word intensity
is occasionally employed as synonymous with depth;
properly, however, it should signify the stronger or
feebler force of the sensation. In addition to the
fineness of the discriminative power of sight in these
several respects, visual sensations are in a high degree
capable of being retained in memory and recalled in
imagination. In fact, so superior in vivacity are the
representations of this faculty to those of the other
senses, that some writers have been found to deny,
but without adequate grounds, the existence of any
other kind of images. The eye, though surpassing the
other senses, is less delicately sensible to the duration
of the stimulus than the ear. The persistence of
positive after-images exhibited in the continuous im-
pressions produced by the rapid circular movement of
a bright object, prevents us from discerning more than
five or six successive excitations in the second.

Cognitional importance. — These numerous capabilities
would be sufficient of themselves to secure to sight
high cognitional rank, but it is to the fact that the eye
aftbrds an immediate presentation of surface extension^
that its fundamental importance as a source of objective
knowledge is due. The apprehension of colour neces-
sarily involves that of space in two dimensions. It is
undoubtedly true that originally the single eye, if it
remained in a fixed position, could have apprehended
but a very limited quantity of surface, that its precep-
tion of shape would have been extremely vague, and
that it could have afforded no information at all as
regards distance; but nevertheless the sensation of
colour necessarily implies some perception of extension.
The point will be made clearer when we come to treat
of the development of sense-perception ; here, however,
we would note that the means by which our visual
perceptions of shape and distance are elaborated, and
our apprehension of surface enlarged, are changes in
the position and form of the eye made known to us by
muscular sensations. The movement of the axis of
the eye round the object viewed, the convergence of the
two eyes varying with its distance, the self-adjusting


process by which the optical lens is flattened or
rendered more convex so as to focus the object upon
the retina, are accompanied by faint feelings of tension
which play an important part in giving precision to
our spatial cognitions. In mature life the "local"
sensibility of the retina is very fine. Close to the
centre of the yellow spot irritations as near together as
•004 mm. are felt as distinct ; but the discriminative
power diminishes as we pass towards the circum-
ference. The size of the retinal image, of course,
decreases with the distance of the object, still this
extreme delicacy of the retina to the local character
of the irritation enables the eye to become a very
perfect instrument for the accurate appreciation of

Capacity for pleasure and pain. — As a direct source of
pleasure or pain visual sensations rank probably lower
than those of any other faculty, though indirectly they
may contribute much to our happiness. Bright lights
and hues are pleasing, and harmonious combinations
have an agreeable effect. A strong glare of light is
painful, but the feeling is organic rather than visual.
Prolonged confinement in the dark produces an intense
desire for light and great joy on first restoration to
liberty, but the pleasure soon fades. The contempla-
tion of the beauties of nature and art affords rich and
refined delight, but here the effect is of an intellectual
and emotional character, and not merely an immediate
function of the sense.

The Senses compared. — In our last chapter we
remarked on the inverse ratio subsisting between the
perceptional and the pleasurable or painful capacity of
the senses. Glancing back at them now, when they
have been separately passed under review, and their
chief features described in detail, the truth of that
observation will be realized. If we divide our tactual
consciousness into the two great groups, the organic
sensations, including the feelings of temperature on the
one side, and the muscular feelings and sensations of
touch proper on the other, and proceed to arrange
them first according to emotional, and then in regard


to cognitional rank, we shall find that the two schemes
will assume virtually an inverse order. Viewed as
direct sources of pleasure and pain, starting from the
highest they seem to stand thus : organic sensation,
taste, smell, hearing, muscular and tactual states, and
sight. But marshalled as instruments of objective
knowledge the order is reversed : sight, tactual and
muscular sensations, hearing, smell, taste, and lowest,
the organic feelings. This classification regards only
the immediate or direct emotional and cognitional
properties of the consciousness of each sense, and the
intrinsic difficulties of all such comparison would pro-
bably cause diversity of view about the former scheme ;
still, estimated from this limited standpoint, it seems to
us approximately correct.

Indirectly, indeed, sight is a much more important
source of pleasure and pain than the sense of smell,
and the knowledge of the universe acquired by hearing
far exceeds that gathered from the actual experience
of all our other senses combined ; but in both cases we
have merely appropriation of the results attained by
the other faculties, and extension of these results by
means of association and inference. Viewed purely
as a state of feeling, a sensation of colour or sound
can afford much less pleasure or pain than an agreeable
odour, or a nauseous stench. Similarly, the sensations
of hearing are more precise, more finely discriminable,
and more vividly revived in imagination, not only than
those of taste and smell, but even than our tactual and
muscular consciousness. Yet, inasmuch as they give
us immediately no assurance of the reality, or of the
extension of the material world, they must be ranked
cognitionally higher than taste or smell, but lower than
the combined muscular and tactual sense. Touch,
indeed, since it reveals the mechanical properties of
the world, has claims to stand even before sight as an
instrument of objective cognition, and it is certainly
more necessary ; still, the immense range of the latter
faculty, its perfect presentation of the geometrical
relations of the universe, and the delicacy of its other
cognitive capabilities have led us to place it at the head


of the list. We need not attempt any further justifica-
tion of the arrangement adopted, as the reader, by
returning on our treatment of the senses separately,
may ascertain the various considerations which have
led to our conclusion. ^^

The ♦' Law of Relativity."— The quality and intensity of a
sensation are affected not only by the character of its own
stimulus, but also by the quality and intensity of other simul-
taneous or immediately preceding sensations. Thus the same
water is apprehended as hot or cold if the hand has been
previously dipped in a liquid of lower or higher temperature.
The same article may feel smooth or rough, heavy or light,
according to the opposite character of the previous experience.
After tasting a bitter substance water appears sweet. The
sudden cessation of a prolonged noise has a startling effect,
as when the miller is awakened by the stopping of his mill.
A black object produces a stronger impression when seen
after or in the midst of a white field, and the several colours
are felt more deeply " saturated," that is, come out richer and
fuller when observed at the same time or immediately
subsequent to those of complementary hue. In general
contrast, whether simultaneous or successive, intensifies the
force of sensation.

On the other hand, the effect of protracted stimulation of
a sense diminishes and may finally cease to be noticed. We
are ordinarily unconscious of the contact of our clothes, of
the pressure of our own weight upon our limbs, of the
continuous hum of the city, of the smell of flowers, or of the
oppressiveness of the atmosphere in a room where we have
been for some time, and, speaking generally, of any constant
uniform excitant.

This influence of variation upon consciousness has been
called by recent psychologists the " Relativity of Sensation."
It is a well-known experience in our mental life, and a consi-
derable factor in our pleasures and pains. It was familiar to
Aristotle and the Schoolmen, who, on account of its effects,
laid down the rule that to secure correct apprehension the

'•''' Balmez, Fundamental Philosophy, Bk. II. cc. x. xi. maintains
the inferiority of touch to sight and hearing from a cognitional
point of view. He does not, however, distinguish sufficiently in
this question between the direct or immediate efficacy of a sense
and that which is merely mediate. In range and representative
power the more refined senses vastly surpass touch, but to a very
large extent their wealth is built upon the capital supplied by the
more fundamental faculty.


several sensuous faculties must be in a neutral or normal

But the sweeping generalization erected upon these facts
under the title of the Law of Relativity is untenable. Accord-
ing to this doctrine, at least as expounded by some of its best-
known advocates, all consciousness is merely /^^//;i^ of difference
or change. Thus Hobbes asserted that " to be always sensible
of one and the same thing is the same as not to feel at all."
Dr. Bain writes : " The Principle of Relativity, or the neces-
sity of change in order to our being conscious, is the ground-
work of Thought, Intellect, and Knowledge as well as Feeling.
. . . We know heat only in the transition from cold and vice
versa. . . . We do not know any one thing in itself, hut only the
difference between it and another thing. . . . The present sensa-
tion of heat is in fact a difference from the preceding cold."^''

Criticism. — To us it seems clear that whilst change — ■
motiis de potentia ad actum, as the scholastics termed it — is an
essential element in the aivakening of sensation, and also an
important factor in its vividness, it is, nevertheless, the very
reverse of the truth to assert that all consciousness is a
"feeling of difference." In sensation we are primarily
conscious of a positive quality, for instance, of a sound or of
a colour, not merely of the relation between two feelings.
All comparison presupposes the perception of the terms to
be compared, and the primitive act of the sense is not com-
parative, but simply apprehensive. What man's conscious-
ness would be like if he always had but one imvarying form
of sensation we do not pretend to know ; but experience
shows that we may continue aware of a uniform stimulus, for
example, of a musical note for an indefinite time if it be not
submerged or crowded out by other feelings,^^

^♦^ " Sicut tepidum in comparatione ad calidum est frigidum; in
comparatione ad frigidum est calidum. . . . Et oportet quod sicut
organum quod debet sentire album et nigrum neiitrum ipsorum
hahet actii sed utrumque in potentia; et eodem modo in aliis sensibus."
(St. Thomas, De Anima, Lib. ii. lect. 23. Cf. also Dc Somniis, lect. 2.)

^^ Cf. Senses and Intellect, p. 321 ; Emotions and IVill, p. 550 ; Body
and Mind, p. 8i ; also Hoffding, Outlines, pp. 114 — 117, and Wundt,
op. cit. pp. Ill — iig.

^^ Mr. J.Ward has forcibly argued against the supposed law:
(i) That the axiom, Idem semper sentire et non sentire ad idem recidiint,
though a truism in reference to the totality of mental life, or to con-
sciousness as a whole, is false as regards many individual impressions.
(2) That the suggested illustrations, e.g., insensibility to continuous
motion, temperature, pressure of the air, &c., are cases of physio-
logical, not psychical habituation, and so are not constant mental
impressions at all. (3) That " constant impressions" in the form



The actual facts on which the " Law of Relativity " and
*' Law of Contrast " are based seem to receive a simple
physiological explanation in the enfeebling effect of fatigue
upon the sense-organ and nerves engaged. These latter

Online LibraryMichael MaherPsychology: empirical and rational → online text (page 9 of 63)