Fact and Fable in Psychology

by Joseph Jastrow

In the experiences of daily life we have to do not with simple sensations, but with more or less complex inferences from them; and it is just because these inferences go on so constantly and so unconsciously that they are continually and persistently overlooked. It is an occasional experience in raising a water-pitcher to have the vessel fly up in the hand in a very startling manner,—the reason for this being that the pitcher, which one is accustomed to find well filled, happens to be empty. This experience shows that we unconsciously estimate the force necessary to raise the vessel, but only become conscious of this train of inference when it happens to lead to conclusions contradictory of the fact. The perception of distance, once thought to be as primitive a factor in cognition as the impression of a color, is likewise the result of complex though unrealized inferences; and the phenomena of the stereoscope, by imitating the conditions of the perception of solidity and thus making us see as solid the flat representations of a pair of diagrams or photographs, furnish a brilliant illustration of the variety and complexity of such unconscious reasonings. As for essential purposes normal persons have a common anatomy, a common physiology, and a common psychology, it results that we draw these unconscious inferences after the same pattern; and so completely are they the outcome of the normal reactions to our common environment, that we need not be, and as a rule are not, aware of their existence until—and probably with some little effort—our attention is directed to them. Unconsciously and spontaneously we learn to see,—that is, to extract meaning out of the sense-impressions that fall upon the retina.

The simplest type of a deception occurs when an inference or an interpretation of this type, owing to an unusual disposition of external circumstances, leads to a conclusion which other and presumably superior testimony shows to be false. Thus, in the observation which Aristotle knew and described, that a pea or other round object held between two fingers crossed one over the other seems double, it is the unusual position of the fingers that induces the illusion. Under ordinary circumstances a sensation of contact on the left side of one finger and on the right side of the finger next to it (to the right) could only be produced by the simultaneous application of two bodies. We unconsciously and naturally make the same inference when the fingers are crossed, and thus fall into error—an error, it is important to observe, which we do not outgrow but antagonize by more convincing evidence. The pea held between the crossed fingers continues to feel like two peas, but we are under no temptation to believe that there really are two peas.

The limitations of our senses lead directly to the possibilities of their deception, which may in turn be realized inadvertently or utilized intentionally. We appreciate how defective is our localization of sound when we attempt to find a cricket by locating whence proceeds its chirp; the same difficulty lends uncertainty to the determination of the direction of fog-horn signals of passing steamers. This uncertainty coöperates in the illusions of ventriloquism; it is involved in the smack which one clown gives another, but which is really the clapping of the hands of the supposed victim; it produces a realistic effect when a cannon is fired on the stage, for it is necessary only to show the flash while the noise is produced behind the scenes. Again, the stimulation of the retina is ordinarily due to the impinging upon it of light-waves emanating from an external object. Accordingly, when the retina is disturbed by any exceptional cause, such as a blow on the head or an electric shock to the optic nerve, we have a sensation of light projected outward into space. The perception of our own locomotion, which is likewise a highly inferential process, offers illustrations of casual illusion and of artificial deception. When on a train, it is by the passing-by before our eyes in the opposite direction of trees and posts and other features of the landscape, that we realize that we are moving forward; accordingly, when a train alongside moves out before our own train has started, we have a distinct realization that we are moving backwards so long as we look at the forward-moving train. There is an illusion devised for amusement called the "Magic Swing," in which one is apparently swung to and fro with wider and wider excursions until a complete revolution is apparently made from a vertical to a horizontal, through the antipodal position, back to the horizontal and the normal. In reality, only a slight motion is imparted to the swing, but the inclosing walls, which are painted to represent a forest scene, are themselves revolved forward and then backward about the axis from which the swing is suspended. As, however, we have no experience with oscillating trees, we unconsciously infer the oscillations to be and feel them in our own persons. In another application of the same illusion we seem to be let down into the bowels of the earth; but after a slight actual descent the car remains stationary while the illuminated sides of the shaft, which are suitably painted, are moved panorama-like in an upward direction. In brief, we are creatures of the average; we are adjusted for the most probable event; our organism has acquired the habits impressed upon it by the most frequent experiences; and this has induced an inherent logical necessity to interpret a new experience by the old, an unfamiliar by the familiar. In describing illusions of the above type, Mr. Sully aptly says that they "depend on the general mental law that when we have to do with the unfrequent, the unimportant, and therefore unattended to, and the exceptional, we employ the ordinary, the familiar, and the well known as our standard." Illusion arises when the rule thus applied fails to hold; and whether or not we become cognizant of the illusion depends upon the ease with which the exceptional character of the particular instance can be recognized, or the inference to which it leads be opposed by presumably more reliable evidence.

II

To make things seem more wonderful than they are, to possess knowledge and exhibit power beyond the ken of the multitude, has exercised a fascination upon the human mind in all its stages of development. The primitive conjuring of the ancient priest or of the savage medicine-man, the long tradition of Oriental legerdemain, and the stage performances of the modern prestidigitateur are all connected with deep-seated human instincts. It has even been suggested[3] that the mimicry and death-feigning instincts of animals, though essentially biological in type, are yet related to the psychological instincts of deception which make their first clear appearance in the higher animals and assume a distinctive position in the psychological equipment of childhood. The conjuring tricks or paradoxes which apparently contradict or rise superior to ordinary experience, furnish the most various types of illustration of the psychology of deception. Whether presented as miracle by priest or by thaumaturgist or by expounder of the black art, or presented as proof of spirit agency by the modern spiritualistic medium or his less pretentious predecessors, or by the stage performer for entertainment, the analysis of what was actually done, and the accounts of what the spectators saw or believed that they saw, illuminate with striking brilliancy the modus operandi of the processes whereby appearance takes the semblance of reality and observation is shrewdly led astray. The conjurer thus becomes a suggester and an actor, not a mere exhibitor of his manipulative skill.

As our present purpose is to investigate the nature of real deception, of the formation of false beliefs which may in turn lead to unwise action, it will be well to note that even such elementary forms of sense-deceptions as those just noted may fall under this head. No one allowed the use of his eyes will ever believe that the pea held between the crossed fingers is really double, but children often think that a spoon half immersed in water is really bent. Primitive peoples believe that the moon really grows smaller as it rises above the horizon; and the ancients could count sufficiently upon the ignorance of the people, to make use of mirrors and other stage devices for revealing the power of the gods. The ability to correct such errors depends solely upon the possession of certain knowledge or of a confidence in its existence.

Continuing with deceptions dependent upon exceptional external arrangements, we may find in conjuring tricks simple and complex illustrations in great perfection. When wine is turned into water, when two half-dollars are rolled into one, when a box into which an article has just been placed is immediately opened and found to be empty, when a handkerchief is torn and made whole again, when the performer drives a nail through his finger, when a coin suddenly appears out of space at the end of a wand, when a card which you have just assured yourself is the ace of hearts on second view is the king of spades, when a bowl filled with water in which goldfish are swimming is produced from under a handkerchief, when a child rests horizontally in mid-air supported only on one elbow,—you are misled or mystified or deceived in so far as you are unaware that the wine was potassium permanganate and sulphuric acid, and was clarified by sodium hyposulphite; that the one half-dollar is hollow and the solid one fits into it; that the box has a double bottom controlled by a secret spring; that the real handkerchief was not torn but another substituted for it; that the nail has been replaced by one that fits around the finger; that the wand is hollow, and a spring controls the appearance or withdrawal of a split coin at its other end; that one half of the card is printed on a flap which, by falling down, shows another aspect; that the bowl covered with a rubber cap was secreted under the coat of the performer; that the child wears a steel suit fitted with joints that lock and become rigid. All these are technical devices which amuse us by the ingenuity of their construction, and, though they may be most baffling, provoke about the same type of mental interest as does a puzzle or an automaton. Ignorance of this technical knowledge or lack of confidence in its existence may convert these devices into real deceptions by changing the mental attitude of the spectator. However, the plausibility of such performances depends so much upon their general presentation that they seldom rely for their effectiveness solely upon the objective appearances presented. They are given a dramatic setting, or put forward as examples of newly discovered forces or of magical control; and this makes them far more effective than this bare account would suggest.

Asking the reader, then, to bear in mind the very great number and ingenuity of such devices, and insisting once more that the only complete safeguard against being misled by them to the extent of forming false conceptions of their modus operandi, is the acquisition of the purely technical knowledge that underlies their success, I shall cite in detail a trick combining illustrations of several of the principles to be discussed. Several rings are collected from the audience upon the performer's wand; he takes the rings back to the stage and throws them upon a platter; a pistol is needed, and is handed to the performer from behind the scenes; with conspicuous indifference he hammers the precious trinkets until they fit into the pistol. A chest is hanging on a nail at the side of the stage; the pistol is fired at this chest, which is thereupon taken down and placed upon a table towards the rear of the stage. The chest is unlocked and found to contain a second chest; this is unlocked and contains a third this a fourth. As the chests emerge they are placed upon the table; and now from the fourth chest there comes a fifth, which the performer carries to the front of the stage and shows to contain bonbons around each of which is tied one of the rings taken from the audience. The effect is most startling. This is the appearance of the trick from the audience. Now let us consider what really takes place. In the hand holding the wand are as many brass rings as are to be collected. In walking back to the stage the genuine rings are allowed to slip off the wand and the false rings to take their places. This excites no suspicion, as the walking back to the stage is obviously necessary, and never impresses one as part of the performance. The pistol is not ready upon the stage, but must be gone for; and as the assistant hands the performer the pistol, the latter transfers to the assistant the true rings. The hammering of the false rings is now deliberately undertaken, thus giving the assistant ample time to tie the true rings to the bonbons; and, while all attention is concentrated upon the firing of the pistol, the assistant unobtrusively pushes a small table on to the rear of the stage. This table has a small fringe hanging about it, certainly an insignificant detail, but none the less worth noting. The chests are now opened, and, after having shown the audience that the second chest comes out of the first, the third out of the second, and so on, the performer can very readily and quickly draw the last, smallest chest from a groove under the table, where it was concealed by the aforesaid fringe, and bring it forward as though it had come out of the next larger chest; this smallest chest is opened and the trick is accomplished. So thoroughly convinced is the observer by the correctness of his first three inferences that the last box came out of the one before it, that I venture to say this explanation does not occur to one person in many thousand, and that most of the audience would have been willing to affirm on oath that they saw the last box so emerge. The psychology of the process, then, consists in inducing the spectator to draw the natural inference, which, in this case, it has been carefully arranged shall be a wrong one.

Deception becomes real according to the skill with which the conditions of reality are imitated. The dexterity and training of the professional conjurer are measured by the fidelity with which he mimics the movements which are supposed to be done. The life-likeness of the movement with which the late Hermann could take up an imaginary orange with both hands from a table (the orange was really let down in a trap on the table as the hands were placed over it), and carry it over to another table where it mysteriously disappeared or passed through a hat, was quite irresistible. Equally so was his palming, or his production of objects from his person, or out of the air, or in out-of-the-way places. The mimetic movements accompanying these actions were so vividly realistic, the misdirection of the attention was so perfect, as to produce a complete hallucination of the appearance of objects from places from which they never emerged. When this was preceded by an actual sleight-of-hand movement, a true hallucination resulted; for example, in the trick of the flying cards which were skilfully thrown to all parts of the auditorium, a card was occasionally thrown which seemed to disappear mysteriously in mid-air; but in reality no card had been thrown but only the movements of throwing it imitated. A rabbit was tossed up in the air two or three times, and then disappeared at the report of a pistol; in reality the rabbit was not tossed at all on the last apparent throw, but was slipped into the hollow of the table.[4]

The more closely the conditions that lead to correct inferences in ordinary experiences are imitated, the more successful will be the illusion; and a useful principle of conjuring illusions is to first actually do that which you afterward wish the audience to believe that you continue to do. Thus, when coins are caught in mid-air and thrown into a hat, a few are really thrown in; but the others are palmed in the hand holding the hat, and allowed to fall when the other hand makes the appropriate movements. Some of the rings to be mysteriously linked together are given to the audience for examination and found to contain no opening, the audience at once concluding that the rings which the performer retains are precisely like them. In general, to gain the confidence of the person to be deceived is the first step alike in sleight-of-hand and in criminal fraud.