— Cf. H., Lesson X.
In all cases of space illusion, the final appeal is to The final the eye. Not to the unassisted eye; for that is itself ^hf eye. subject to illusion: but to the measitring eye, — the eye armed with a ruler and a pair of compasses. What touch and sight tell us of the world of space may, as we have learned by experience, be very far from right. What sight tells us under the conditions of measurement we believe to be true; the railway lines are parallel, the table is a parallelogram, the verticals of Fig. 1 1 are equal, the square is equilateral, — in spite of all appearances to the contrary, — because the measuring eye tells us so. Measured or mathematical ' seeing' is always * believing.'
Fig. II / 1 1 8 Perception Questions and Exercises (i) Qualitative Perceptions.
1. The middle c of the piano contains, as overtones, the c and g of the next higher octave, and the c^ e and g of the octave above that. Strike some one of these over- tones softly, by itself. Then strike the middle c loudly, and try to hear in it the overtone which you sounded a moment before. If you think you can, sing the over- tone, and then strike the note to make sure that you have it correctly.
2. Have a number of chords struck on the piano: chords of two, three, four notes, in random order. After a chord has been struck, ask yourself how many notes it con- tained. Continue the practice until you can distinguish accurately a two-chord from a three-chord, etc.
3. Try, by introspection, to find out what sensations are contained in the following perceptions: hardness, wet- ness, roughness, the ^ taste ' of tea, the ^ taste ' of lemon- ade. Make several trials of the perceptions themselves, and then introspect them.
(2) Spatial Perceptions. ^^~ 4. Have yourself touched, while your eyes are closed, at various parts of the body. How do you know where you are touched? Introspect very carefully.
5. If you were touched on the wrist and on the chest, and tried (with your eyes shut) to re-touch the places struck, you would get more nearly right on the wrist than you would on the chest. Why?
6. Close your eyes. Let the experimenter take a pair of blunt-pointed drawing compasses, and set the points down evenly upon your wrist, crosswise. If the points are near together, you will ^feel' only one pressure; if they are a certain distance apart, two pressures. The experimenter must alter the distance between the points, little by little; in one series beginning with a distance that clearly gives one, and in a second series with a distance that clearly gives two pressures; until he finds the distance at which oneness passes over into twoness. This distance, averaged from the tw^o series, gives a Questions and Exercises measure of your ability to distinguish places upon the skin. — Compare the wrist distance with similar dis- tances upon the forehead, cheek, and back of the neck. What conclusions do you draw from the difference between the distances?
7. Combine a number of double pictures in the stereoscope. Note carefully how the pict- ures on the two halves of the slide differ. When you have grown used to the in- strument, try to combine simple pictures (the common outline drawings of truncated cones or pyramids) by the unaided eye. Look straight through the slide, towards a point beyond it; and move the slide back and forth, Fig. 12 until the pictures coalesce. It is a good plan to prac- tise this ^free stereoscopy' with transparent (celluloid) slides; the drawings you can easily make for your- self in ink.
The Stereoscope (Fig. 12). — Light is reflected to the eyes, along the dotted lines, from the two pictures, a, b. The reflected rays are so refracted by the prisms, ^, d^ that they appear to come from a single point, ^, lying on the far side of ^, b. Hence we see at ^ a single picture, formed by the superposition of the two pict- ures, a and b.
8. Put one of the photographic slips in the drum of the stroboscope and twirl it swiftly, so that you can get the illusion of movement. Then begin again, moving the drum at first very slowly, and later on more quickly; so that you build up the illusion in stages. Notice each stage. — Explain the illusion {cf. Experi- ment 5, p. 53 above).
The Stroboscope (Fig. 13). — A cardboard drum, a, open above, can be twirled upon the handle,^. The Perception 9- upper half of the wall of the drum is pierced at regular intervals by vertical slits. The lower half is covered, on the inside, by a slip of paper upon which the sepa- rate phases of some movement (the flight of a bird, the gallop of a horse) have been drawn or photographed. As the drum turns, one looks down, through the slits upon the inserted slip. Aristotle suggested the following way of proving that the final appeal in space matters is to the eye. Cross the second over the a first finger of your right hand. Place a pencil between the crossed joints. Since, under natural conditions, the outsides of the first and second fingers never touch the same object, the skin tells you that two objects are now in contact with it. The eye contradicts the skin; and so strong is the contradic- tion that you do not even ^ feel ' the pencil as two objects while your eyes are open.
Now shut your eyes, and let the experimenter put either one thing or two things between your crossed fingers, as he chooses. Not knowing whether you are ' feeling ' one thing or two, you cannot appeal to a mental picture. The result is that the skin has its own way, and you soon ^ feel ' two objects in every experiment, whether one or two be really between your fingers.
N. B. — This account of Aristotle's experiment holds only for those to whom the experiment is new. If you have practised it as a child, you will get the twoness of the pencil at once whether your eyes are open or not. Draw two semicircles, of i cm. radius, in the posi- Questions and Exercises 121 tion Q (^. Draw the diameter to the left-hand curve. This seems now to indude less space than the other, open semicircle. Why?
11. It is very important to realise the difference between touch-space and skin-space. Take a piece of stiff card, with a smooth edge of 12 cm. Cut pointed teeth along the edge. Estimate the length of the jagged edge, with closed eyes, (i) by passing the finger along the points (touch), and (2) by having the teeth pressed down upon the skin of your fore- arm (pressure). You will think that the card is longer than it looks to be, in the first case, and shorter than it looks to be, in the second.
(3) Temporal Perception.
12. Shut your eyes, and hold a watch to your ear. See how many rhythms you can throw the ticks into. Write down the forms and accents of the rhythms.
13. Close your eyes. Let the experimenter draw a pencil, at an even rate, from your elbow to the tip of the middle finger. The pencil seems to travel more quickly at some places than at others. Draw a fig- ure of the arm, and mark in the places of apparent slowing and quickening. Explain by reference to (4) Why is the mixed perception termed an ^assimilation'.?
(5) If sensations of taste and of temperature have not the attribute of extent, how do you explain their apparent extensity?
(6) It is said above, § 42, that qualitative perceptions have undergone less change than those of space and time. What change have they undergone? How is it that this change has not deprived them of their value?
References James, Textbook^ chs. xx., xxi. Sully, HuiTian Mind^ vol. I., ch. viii. Titchener, Outline^ §§ 43-51. Wundt, Lectures^ Lects. VIII. -XIII. Wundt, Outlines^ §§ 8-1 1.
See also: Sanford, Course^ Pt. i., 1897; Am. Journ. of Psych. ^ CHAPTER VII Idea and the Association of Ideas Idea as § 50. The Development of Ideas. — The ideas of the of percep- pnmitive mmd are, as it were, photographic copies, tion. Hfe-Hkenesses, of the perceptions which go before them. Thus the idea of a landscape would be in part a picture-idea, the look of stream and hills and trees; in part a sound-idea, the idea of splashing water and rustling boughs; in part a tactual idea, the ' feel ' of springing grass and moving wind; in part a smell-idea, a remembered freshness and fra- grance of air and flowers. The life-likeness is, of course, never perfect: the idea is weaker, passes by more quickly, and is more sketchy, than the percep- tion that corresponds to it: but the qualities of the perception are found again in the idea. Produced in perception, they are rep^'odiLced in idea. Idea as This, howcvcr, is only the first stage in the develperception opmcnt of the idea. The bram-cortex has m most cases a tendency to work more easily at one part than at another. Or — to speak in terms of mental constitution — minds are so constituted that their processes run more easily along certain channels than along others. Hence it happens that those elements in a perception which do not fit in with our mental constitution are very soon dropped out of the idea; the idea is a copy or life-likeness of only a part of the perception. And further, if the nervous tendencies are strongly marked, ideas may cease to be even partial copies of perceptions. Just as we translate words and sentences from one language into another, so may the nervous system translate a perception into more familiar terms, — into an idea which has none of the qualities that were contained in the perception, but replaces them by other and more familiar qualities that mean the same thing.
, We describe the differences between minds whose Memory- ideas are still at least partiaL copies of perceptions ^^^^ 'by saying that they show differences of vtemory-type. Such minds have a preference, so to speak, for a par- ticular kind or type of idea: for picture-ideas, sound- ideas, etc. Minds of the second order, those whose ideas are translations out of the language of percep- tion into an entirely different language, belong for the most part to one or other of the verbal sub-types, and sub- For the language into which their perceptions are ^^^^' translated is nearly always a language of words; their ideas are word-ideas, no matter what the per- ceptions may have been.
We have now to examine these types and sub- types, in order to see what the ideas are that make up the individual consciousness in each case.
§ 51. The Four Chief Memory-types. — The two most highly developed senses are those of sight and hearing. It is natural, then, that there should be minds which are almost wholly eye-minds or ear- minds: eye and ear furnish so many differences of sensation quality that they are able of themselves to represent a great many aspects of the physical world, without calling in help from the other sense-organs.
A Idea and tJie Association of Ideas Auditory type.
Visual type. (i) If the mind is of the visual or eye type, all its thoughts and memories and imaginations will consist of ideas of sight. If, e.g.^ an operatic performance is recalled, the scenes will be pictured, and the dress and movement of the performers seen over again; but the music will not be remembered. The sound- parts of the perception have dropped out, and only the sight-parts are left. The mind of the inventor is likely to be predominantly of this type: he sees the machine that he is designing, in the mind's eye, before it has been built. (2) If, on the other hand, the mind is of the auditory or ear type, its memories will be memories of things heard, and not of things seen. Stage and performers will be forgotten, and only the music remembered. Friends will be thought of not as pictures, figures of a certain appearance clothed in a certain way, but as sounds, as voices or footsteps. The minds oi^prators and of musical com- posers may be of this type. Every one knows the story of the deaf Beethoven's playing, the tears roll- ing down his cheeks as he heard in idea what he could not hear in outward perception. And it is most useful to the public speaker to be able to hear his coming sentences, with their right ring and emphasis upon them, before he actually delivers them to his audience.
Tactual type. (s) There is another group of perceptions, — not so rich in sensation qualities as the perceptions of sight and hearing, but still of great importance for our knowledge of the external world, — which fur- nishes a third memory-type: the tactical or (as it is less well called: § 46) 7notor type. Tactual perceptions are made up of the sensation qualities that come to us from skin, muscle, tendon and joint: they are perceptions of hardness and softness, roughness and smoothness, resistance and effort, movement or position of the limbs, etc. It is plain, however, that useful as tactual ideas (life-likenesses of tactual per- ceptions) may be, a mind made up of them and of them alone will be very much at fault in its thoughts and memories. True, it will be useful for the iiivejitor to have the power of ' feeling ' in himself the pulls and stresses and strains to which the various parts of his machine must be subject; but he will hardly be able to design the machine unless he can see it as well as ' feel ' it. And indeed, the pure tactual type is rare. Either it reduces to the verbal sub-type (§ 52), or it is one of the types represented in the mixed type which we now pass to consider.
Cooks and confectioners are employing a pure tactual memory when they judge by stirring that a dough or batter has attained the right consistency. But this mode of judg- ment is confined to a few special cases. Even when one picks out chords or airs on the piano by finger-memory, one is always guided, to some extent, by hearing; the tactual memory is mixed with auditory. This, however, does not detract from the value of the tactual memory; it is, as every player knows, of great importance to the pianist.
(4) The last of the four chief memory-types is the Mixed type, mixed type. When a mind is of this constitution, the sensation tendencies of the nervous system are more or less evenly balanced. The operatic perform- ance is remembered in all three ways, as something seen, as something heard, and as something ^felt'; 126 Idea and the Association of Ideas stage and performers are visible once more, voice and orchestra are heard again, and the ease or diffi- culty with which the singers reached their high and low notes is sympathetically revived in one's own throat muscles. This is the most useful memory- type, simply because it gives the most complete account of the outside world, because it reproduces the event thought of under the greatest variety of aspects. But an equal balance of tendencies is rare: even when a mind is to be classed as * mixed ' in type, experiment generally shows that some one side of it (the eye-side, ear-side, etc.) is more strongly devel- oped than the others.
Importance § 52. The Three Verbal Sub-types. — We said just ideir ' ^^^ ^\\2X words offcr a common language into which all ideas, no matter what their perceptions are com- posed of, may be translateii. Changing the metaphor, we may say that words are the common denominator of all ideas or perceptions, — something in which they may all be expressed.
Every adult mind is made up, to a considerable extent, of word-ideas. We are born into an atmo- sphere of words; we are talked to from our earliest infancy; we learn to talk in the second year of our life. An intelligent child of two years may have a vocabulary of 300 or 400 words; it is on record that an intelligent child of six may have a vocabulary of 2,000. And there is no experience, however uncom- mon or overpowering its incidents, which cannot be expressed in words.
The word-idea has three forms: visual, auditory and tactual. It may be the idea of the word seen, in Verbal sub- print or in manuscript; or the idea of the word auditory, heard, whether in one's own voice or in that of t^^t"^^- another; or the idea of the word 'felt,' whether in speaking (felt in the muscles of the throat) or in writ- ing (felt in the muscles of the hand). The ideas of an eye-mind will, naturally, pass most readily into the visual word form; those of an ear-mind into the audi- tory word form; and those of the tactual mind into one of the tactual word forms.^ Thus the recollection of the operatic performance, in a word-mind, might be a printed account of the music and acting (verbal- visual ideas); or the sound of a voice describing the performance (verbal-auditory ideas); or the * feel ' of the same voice in the throat (verbal-tactual or verbal- motor ideas).
We take our own way of thinking so much as a matter of course, that it is difficult for us to realise how many different ways there are of thinking the same thing. Hence while some part, of the two last Sections will come familiarly to every reader, there will doubtless be other parts which, at first sight, seem almost incomprehensible. A Httle cross- questioning of friends, however, will probably bring all the types and sub-types to light.
At the same time, it is but rarely that we find a perfectly pure type or sub-type. The verbal-tactual occurs, perhaps, most frequently in pure form. The others are almost always mixed, to some degree. Thus the verbal-auditory is usually verbal- tactual as well; and the verbal-visual generally has a trace of the verbal-auditory, and so of the verbal-tactual. This complexity of mental constitution is easily understood^ when we remember the great complexity of the nervous system, and the large number of sense-channels through which the outside world gains access to consciousness.
Idea and tlie Association of Ideas Reproduc- tion of smells and tastes is rare.
Organic type.
§53. The Minor Memory-types. — The ideas of taste and smell are very seldom copies of their per- ceptions. In the life of primitive man, taste and smell have an important function to discharge (§ 20); and even to-day their sensations and perceptions affect us strongly (§ 25). But as civilisation advances, we depend less and less upon them and more and more upon verbal knowledge, — upon what we read in books on diet, or upon what our physician tells us. Hence life-likenesses of taste and smell qualities are not included, as a rule, in our stock of ideas.
Try to recall the scent of a rose. You have, probably, a picture-idea of the flower, and a tactual idea of the contrac- tion of the nostrils in sniffing. Perhaps you actually do sniff; so that you perceive this contraction, and get sensa- tions of pressure and temperature from the air inhaled. Perhaps, too, the word ' rose ' comes to mind, either alone or combined with some other word that suggests the rose scent, — ^ attar ' or ' essence ' or ' perfume.' But the scent itself is, in all probability, not present in the idea.
It is possible that, with continued practice, the power of im- aging scents could be regained. Oftentimes on entering a room we have an ilhision of smell: we say, " Don't I smell sandalwood " or " heliotrope " or what not. This fact seems to show that scents are, even now, occasionally recalled as true smell-ideas, life-likenesses gf perceptions. For the most part, however, the power is unemployed, if not lost.
We can hardly speak, then, of a smell-type or a taste-type. On the other hand, the 07'ganic type is of some importance. There are people who, in re- calling an event of their past experience, revive or repeat the internal bodily attitude in which they met the event. It is not that they set to work deliber- ately to reproduce the * sinking of the stomach ' and heart-beat and internal tremors and quiverings which accompanied the original experience; but rather that, when they recall this experience in the form most natural to them, — visual, auditory, etc., — the inter- nal or organic sensations come up *of themselves,' in perception, along with the pictures or sounds that stand for the experience in idea.
We saw in § 25 that the organic sensations enter with Signs of quite especial readiness into feelinsfs; i.e., have an especial ^^^^"^^ power of attracting the attention. This trait is clearly shown in the memories of the organic type. If a man is greatly moved when he recounts an experience of many years ago, — becoming angry now as he was then, grieving now as he grieved then, etc., — you may be sure that he has an organic memory, whatever his principal type may be. His anger or grief fastens itself to the revived internal sensations. If, on the other hand, he tells you of his past griefs and angers calmly and coolly, you may be sure that there is no revival of the inward stir-up which took place when they were originally felt; there is no organic memory.
Since organic memory shows itself in 2^ feelings it has been 'Affective supposed by some psychologists that the feeling-side of the memory.' original experience is remembered, and that we should speak not of organic, but of affective memory. We have seen, how- ever, that it is impossible to attend to an affection (§ 33); and since we are attentive when we are trying to remember, it is plain that we cannot recall an affection. The affection comes with the organic sensations that make up the internal bodily attitude.''
It is not perfectly correct, either, to speak of organic No true memory. For the organic sensations are not recalled in J^^^amc •^ o « memory.
idea; they are revived, actually set up again in the body, when the memory pictures or sounds come to mind. Still, they colour the memory; it is very different with them from what it would be without them. Hence we may give or- ganic memory rank as a secondary or minor type, though it K 130 Idea and the Association of Ideas cannot be counted with the four chief types of § 51. The organic sensations come up in accordance with the law of the association of ideas, of which we have now to speak.
§ 54. The Association of Ideas. — Sensations are welded together, at the bidding of nature, to form perceptions; and the sensations produced by the presence of an object in perception are reproduced in idea. But as the number of perceived objects increases, it must plainly happen that one and the same sensation will be called upon to do duty in more than one perception or idea. The quality of blue, e.g., belongs to water and sky, to certain flowers and birds, to certain earths and rocks, — to say noth- ing of human productions; it occurs in a vast num- ber of different perceptions. By being used over and over again, in this way, every sensation gets into habits of connection with other sensations; while these, in their turn, form habits of connection with yet others, and so on. The law of Now it is One of the most important laws of mind that all the connections set tip between sensations, by their welding together into perceptions and ideas, teitd to persist. A sensation which has once formed connections with other sensations cannot shake them off and be its own bare self again, — the bare sensa- tion that it was when it entered for the first time into a perception, — but carries its connections about with it; so that whenever it has a place in a conscious- ness, the connected sensations tend to be dragged in also. This law is the law of the association of ideas.
There are various points that we must notice, in regard to this law of association, before we proceed to discuss association.
§ 54- ^^^^ Association of Ideas the two forms of association, the simultaneous and the successive.
(i) Notice that the work of association, the associat/;/!^, is done not by ideas but by sensations contained in ideas. A sen- sation (blue), which is contained in my perception or idea of a lake, is also contained in my idea of M. Bouguereau^s picture, '' Our Lady of the Angels.'' When I see or think of the lake, I think of the picture. The ideas are associated: but it is a sen- sation that does the work.
(2) Notice, on the other hand, that although the sensation does the w^ork it is ideas, meanings, that are associated. My idea of the lake does not call up an idea of the blue in the picture, but an idea of the whole picture. The associat^<^, then, is an idea.
(3) Putting these two facts together, we get the for inula of association: ab-bc. My lake-idea contains the elements a^ b; my picture-idea the elements b^ c. The sensation of blue is con- nected both with a and with c. Hence when I have the percep- tion or idea ab^ the connection of b with c tends to persist, and the lake reminds me of the picture.
(4) In the older psychologies we read of various ' kinds ' of association: association by contrast (^ giant ' suggests ^ dwarf), by similarity (^ Dickens ' suggests ^ Thackeray '), by contiguity (^sea' suggests ^ ships,' because the two are seen together), by cause and effect (the riven oak-tree suggests the lightning that struck it), by means and end (the idea of keeping our clothes unspoilt suggests the taking of an umbrella with us when we go out), and so on. It is clear, however, from what has just been said, that these are not ' kinds ' of association, — there is only one kind, — but merely forms of it, arranged for convenience under certain heads. Every one of the instances given can be brought under the formula ab-bc; the working of the law is the same in each case. We may classify photographs as blue prints and carbon prints and silver prints and platinotypes, as helio- types and collotypes and stannotypes; but the principle of pho- tography, the fundamental law, is the same for all.
(5) Notice that the ab of the formula ab-bc may be a perception^ though we always speak of the association of ideas. It may be the perceived, seen lake that suggests the picture-idea. Similarly, some (though not all) of the elements in the be of the Sensations associate; ideas are associated.
Formula of association.
Forms of association.
Perception and associa- tion.
132 Idea and the Association of Ideas formula may be perceived. When a man whose memory is of the visual and organic types is reminded of a past experience by some present perception, the be of the association consists in part of organic sensations actually set up in the body at the moment of recall, — consists, i.e.j of a perception.
§ 55. Simultaneous Association. — We saw, in the ■ last chapter, that pure perception is very rare in the adult mind. Most of our perceptions are mixed; consist partly of outside and partly of inside sensa- tions. To such a length has the mixture of percep- tion and idea been carried that it is scarcely possible, in some cases, to imagine with any vividness what the original process of perceiving was. We can hardly realise now what the perceptions of place on the skin, . of distance in space and of rhythm were in their first formation; our way of perceiving them is a short cut, a jump at meaning, with most of the steps that our forefathers took left out. Simuitane- The assimilations and symbolic perceptions of our own minds are put together by way of simultaneous association. A material object flashes one of its aspects into consciousness in the shape of a sensation. This sensation has fixed habits of connection with other, central sensations. Hence when it arises, they necessarily arise with it. Doubtless, if we knew the truth, they come some small fraction of a second after it; but the interval is so short as to be altogether unnoticeable. In practical experience, ivhen the sen- sation comes, it comes with a bevy of inside sensations clustered about it.
Suppose that you are strolling along a country road, and suddenly hear a rumbling noise. You know at once that it is coming from behind you, and that it is the noise of a ous associa tion.
§55- Simultaneous Association carriage. You do not turn; but in a few moments, when the noise has reached a certain degree of loudness, you step to the path to make way.
Now sounds do not possess the attribute of extent, and The localisa- so cannot give rise, directly, to space perceptions. Never- ^^"^ ^ theless, you seem here to be placing the noise, and placing it accurately, by a direct perception of its distance and direction. What is the explanation?