[Ill.u.s.tration: FIG. 5.]

White objects appear much larger than black ones. A white square looks larger than a black one. It is said that cattle buyers who are sometimes compelled to guess at the weight of animals have learned to discount their estimate on white animals and increase it on black ones to make allowances for the optical illusion.

[Ill.u.s.tration: THIS MAN AND THIS BOY ARE OF EQUAL HEIGHT, BUT a.s.sOCIATION OF IDEAS MAKES THE MAN LOOK MUCH THE LARGER]

[Sidenote: _Use of Illusions in Business_]

The dressmaker and tailor are careful not to array stout persons in checks and plaids, but try to convey an impression of sylph-like slenderness through the use of vertical lines. On the other hand, you have doubtless noticed in recent years the checkerboard and plaid-covered boxes used by certain manufacturers of food products and others to make their packages look larger than they really are.

The advertiser who understands sensory illusions gives an impression of bigness to the picture of an article by the artful use of lines and contrasting figures. If his advertis.e.m.e.nt shows a picture of a building to which he wishes to give the impression of bigness, he adds contrasting figures such as those of tiny men and women so that the unknown may be measured by the known. If he shows a picture of a cigar, he places the cigar vertically, because he knows that it will look longer that way than if placed horizontally.

[Sidenote: _Making an Article Look Big_]

A subtle method of conveying an idea of bigness is by placing numbers on odd-shaped cards or blocks, or on any blank white s.p.a.ce.

The object or s.p.a.ce containing the figures always appears larger than the corresponding s.p.a.ce without the figures.

This fact has been made the basis of a psychological experiment to determine the extent to which a subject's judgment is influenced by suggestion. To perform this experiment cut bits of pasteboard into pairs of squares, circles, stars and octagons and write numbers of two figures each, say 25, 50, 34, 87, etc., upon the different pieces. Tell the subject to be tested to pick out the forms that are largest. The susceptible person who is not trained to discriminate closely will pick out of each pair the card that has the largest number upon it.

[Sidenote: _Testing the Confidential Man_]

This test can be made one of a series used in examining applicants for commercial positions. It can also be used to discover the weakness of certain employees, such as buyers, secretaries and others who are entrusted with secrets and commissions requiring discretion, and who must be proof against the deceptions practiced by salesmen, promoters and others with seductive propositions.

[Sidenote: _Tests for Credulity_]

This examination can be carried still further to test the subject's credulity or power of discrimination. What is known as the "force card" test was originally devised by a magician, but has been adopted in experimental psychology. Take a pack of cards and shuffle them loosely in the two hands, making some one card, say the ace of spades, especially prominent. The subject is told to "take a card."

The suggestive influence of the proffered card will cause nine persons out of ten to pick out that particular card.

Turning from illusions of suggestion, shape and size, another field of peculiar sensory illusions is found in color aberration. Some colors look closer than others. For instance, paint an object red and it seems nearer than it would if painted green.

[Sidenote: _What Colors Look Nearest_]

Aside from the obvious uses to which these sense-illusions can be put, they form the basis for a number of psychological experiments to test the abilities of persons in many ways. Here is a test which deals with the range of attention. If you desire to discover the capacity of any person to pay attention to unfamiliar questions or subjects which might at some future time have great importance, try this test. Have a piece of pasteboard cut into squares, circles, triangles, halfmoons, stars and other forms. Then write upon each piece some such word as hat, coat, ball or bat. The objects are then placed under a cloth cover and the subject to be examined is told to concentrate his attention on the shapes alone, paying no attention to the words. The cloth is lifted for five seconds and then replaced. The subject is then told to draw with a pencil the different shapes and such _words_ as he may chance to remember. The experiment should then be repeated, with the injunction to pay no attention to the shapes but to remember as many words as possible, and write them down on such _forms_ as he may happen to recall.

[Sidenote: _Testing the Range of Attention_]

Of course, the real object is to determine whether the subject will see more than he is told, or whether he is a mere automaton. The result will tell whether his attention is of the narrow or broad type. If it be narrow, he will see only the forms in the first case and no words, and in the second case he will remember the words but be unable to recall the shape of the pieces of cardboard.

[Sidenote: _A Guide to Occupational Selection_]

His breadth of attention will be shown by the number of correct forms and words combined which he is able to remember in both cases.

In other words, this will measure his ability to pay attention to more than one thing at a time.

Other things being equal, the narrow type of attention belongs to a man fitted for work as a bookkeeper or mechanic, while the broad type of attention fits one for work as a foreman or superintendent or, lacking executive ability, for work requiring the supervision of mechanical operations widely separated in s.p.a.ce.

[Sidenote: _Test for Attention to Details_]

The ordinary man sees but one thing at a time, while the exceptional man sees many things at every glance and is prepared to remember and act upon them in emergency.

Having determined a person's scope of attention, you may want to test his accuracy in details as compared with other men. To conduct such an experiment dictate a statement which will form one typewritten letterhead sheet. This statement should comprise facts and figures about your business of which the subjects to be tested are supposed to have accurate knowledge. After this original page is written, have your typist write out another set of sheets in which there are a large number of errors both in spelling and figures.

Then have each of the persons to be examined go through one of these sheets and cross out all the wrong letters or figures. Time this operation. The man who does it in the quickest time and overlooks the fewest errors, naturally ranks highest in speed and accuracy of work.

[Sidenote: _Other Business Applications_]

Look into your own business and you will undoubtedly find some department, whether it be store decoration, office furnishing, window dressing, advertising, landscape work or architecture, in which a systematic application of a knowledge of sensory illusions will produce good results.

CHAPTER IV

INWARDNESS OF ENVIRONMENT

[Sidenote: _Factors of Success or Failure_]

The aspect of the sense-perceptive process that deals with the relation of mind to environment is of greatest practical value.

Look at this subject for a moment and you will see that the world in which you live and work is a world of your own making. All the factors of success or failure are factors of your own choosing and creation.

If there is anything in the world you feel sure of, it is that you can depend upon the "evidence of your own senses," eyes, ears, nose, etc. You rest serene in the conviction that your senses picture the world to you exactly as it is. It is a common saying that "Seeing is believing."

[Sidenote: _Should Seeing Be Believing?_]

Yet how can you be sure that any object in the external world is actually what your sense-perceptions report it to be?

You have learned that a countless number of physical agencies must intervene before your mind can receive an impression or message through any of the senses.

Under these conditions you cannot be sure that your impression of a green lamp-shade, for instance, comes through the same sort of etheric and cellular activities that convey a picture of the same lamp-shade to the brain of another. If the physical agencies through which your sense-impressions of the lamp-shade filter are not identical with the agencies through which they pa.s.s to the other person's brain, then your mental picture and his mental picture cannot be the same. You can never be sure that what both you and another may describe as green may not create an entirely different impression in your mind from the impression it creates in his.

Other facts add to your uncertainty. Thus, _the same stimulus_ acting on _different organs_ of sense will produce _different sensations_. A blow upon the eye will cause you to "see stars"; a similar _blow_ upon the ear will cause you to _hear_ an explosive sound. In other words, the vibratory effect of a _touch_ on eye or ear is the same as that of _light_ or _sound_ vibrations.

[Sidenote: _Hearing the Lightning_]

The notion you may form of any object in the outer world depends solely upon what part of your brain happens to be connected with that particular nerve-end that receives an impression from the object.

You _see_ the sun without being able to _hear_ it because the only nerve-ends tuned to vibrate in harmony with the ether-waves set in action by the sun are nerve-ends that are connected with the brain center devoted to sight. "If," says Professor James, "we could splice the outer extremities of our optic nerves to our ears, and those of our auditory nerves to our eyes, we should hear the lightning and see the thunder, see the symphony and hear the conductor's movements."

[Sidenote: _Importance of the Mental Make-Up_]

In other words, the kind of impressions we receive from the world about us, the sort of mental pictures we form concerning it, in fact the character of the outer world, the nature of the environment in which our lives are cast--_all these things depend for each one of us simply upon how he happens to be put together, simply upon his individual mental make-up_.

There is another way of examining into the intervening agencies that influence our mental conception of the material world about us.

[Sidenote: _Unreality of "The Real"_]

Look at the table or any other familiar object in the room in which you are sitting. Has it ever occurred to you that this object may have no existence apart from your mental impression of it? Have you ever realized that no object ever has been or ever could be known to exist unless there was an individual mind present to note its existence?

If you have never given much thought to questions of this kind, you will be tempted to answer boldly that the table is obviously a reality, that you have a direct intuitive knowledge of it, and that you can at once a.s.sure yourself of its existence by looking at it or touching it. You will conceive your perception of the table as a sort of projection of your mind comfortably enfolding the table within itself.