This classic article by Pierre Janet was originally published in the Journal of Abnormal Psychology in 1906.
A large number of patients have impulses to perform certain useless, bizarre, and even dangerous acts. At certain moments they feel the desire for these actions arising in them; they have representative images harmonizing with their execution of the act; they even have in the muscles of the body little movements, more or less involuntary, which are like the beginnings of these acts; this is what they mean when they say that they feel themselves urged to perform these acts. However, they are fully conscious of the absurdity of the actions and judge them at their true worth; there is a more or less serious and real struggle between the tendencies which urge them on and their judgment which holds them back. The patients often resist when the act appears to them really bad; they yield when, rightly or wrongly, they regard the act as of little consequence.
Generally, the acts executed in this fashion are not very important, and the patient has the mania of believing himself drawn towards dangerous acts rather than being really drawn to their accomplishment. But, however, in examining, especially the obsessed and the scrupulous, I have, perhaps, gone too far in minimizing the danger of these impulsions; the patient may deceive himself, may let himself go farther than he wishes, and the actions really performed are often of decided importance. However the case may be, the act once performed, the patient experiences a joy, a peculiar satisfaction, and for a time he seems freed from the fatigue and the various painful sensations he constantly suffered before.
These various characteristics of the impulsions it is difficult to explain, and we must not expect to establish a general theory which would account for all the observed facts in different cases of impulsion, or the reasons which urge a patient to desire so vividly such or such an action.
We must not think that all the impulsions in the various neuroses and psychoses have always the same mechanism. For example, it is probable that in certain cases the phenomenon may be explained by a mechanism analogous to that of suggestion: a complex idea, made up of a group of formerly associated images is completely developed in a narrow consciousness, abnormally narrowed because it does not meet enough antagonistic tendencies. In other cases we can apply the known laws of subconscious phenomena which completely develop outside of the field of a retracted consciousness and which enter it only when it is too late, when the development, being too complete, can no longer be easily stopped.
Explanations of this kind are certainly true in some cases, but it does not seem to me possible to generalize, and I think that there are a number of other explanations which must play an important part in any particular case. That is why I should like to point out here, in connection with some interesting cases of impulsions, a disposition of the mind, quite general among the obsessed and impulsive, which plays, I think, a pretty important part in at least a certain number of cases. The observations being rather curious in themselves, we shall give a brief résumé of them, then we shall look for those feelings which are pretty nearly the same in spite of the diversity of the impulsions, and we shall see the part such feelings play in the genesis of the impulsions.
Observation 1. It is sufficient to recall in a few words the well-known phenomena of dipsomania. I take one example among many. A young woman, thirty years of age, of the best society and well educated, has been subject almost since her nineteenth year to certain nervous attacks, very painful to herself and to her family. From time to time, at irregular intervals, which in later years have become shorter and shorter, she experiences an intense desire to drink whisky. At first she takes a few drops secretly, for she well knows that it is dangerous for her; she does not want to yield entirely to her desire, but she simply wants to satisfy it to a small degree by tasting the liquor. The next moment, before she realizes it, she takes more, and thus continues, ashamed and unhappy, to drink in secret more and more. She drinks more than a half bottle a day, and quickly falls into a state of complete intoxication, — into a most shameful stupor, from which she only recovers after several days of real illness. Regaining consciousness with a feeling of profound despair, she speaks of killing herself, and only consoles herself with difficulty, by making the most solemn "promises. In fact, she remains perfectly rational, drinking absolutely nothing but water, when in a few weeks or months the whole affair begins again. This is the classic form of dipsomania; it is needless to dwell on it, for we might easily add here twenty similar cases.
Observation 2. It is interesting to place beside this example a case of impulsion to eat, which is rarer than the impulsion to drink. Here is a young woman, Qe., twenty-six years of age; in coming to see us she brings with her a large bag, and her pockets are filled to overflowing. What is she bringing with her in coming to us for a consultation? It is simply provisions for the journey. She has in her bag and in her pockets several pieces of bread, a few slices of ham, some chocolate tablets, and some sugar. One would say that she was going to cross a desert, when it is simply a question of crossing a few streets. The provisions are indispensable to her, for, especially in the open air and in squares, it is absolutely necessary that she should take something to strengthen her. At the end of several steps she feels dazed, becomes dizzy, chokes, and is covered with cold sweats. The danger would be great if she did not know the remedy. All she needs is to strengthen herself. She eats a piece of ham, puts a piece of sugar in her mouth, and is thus able to take a few more steps. But very soon it all begins again, and it is only with the aid of rolls and chocolates that she is able to cross a square. One can, therefore, understand her miserable plight when her provisions run short. She is obliged at all costs, with unheard-of efforts, to cross the desert to reach an oasis, — that is, a bakery. During this terrible journey she gets along as best she can. What do unfortunate travelers not eat? She may pick Up a raw potato, capture an onion, or a few green leaves; this hardly sustains her, but gives her enough strength to reach a bakery. In general, she prefers to remain at home; that is less dangerous, and so she does nothing else but prepare and eat food all day long. Sad and unhappy, she finds relief only in this continual absorption of food. This condition lasts from ten to fifteen days, rarely longer. She then becomes calm, no longer experiences the need to eat, and is obliged to take care of the gastritis which she has acquired in consequence of the overloading of the stomach. She remains rational; eats moderately, even little, for several weeks or months; then, all of a sudden or gradually, as the case may be, the same comedy begins again.
Bulimia is rare in this typical form, which, as we see, is entirely analogous to the attacks of dipsomania; but it often exists in an attenuated form among many neuropaths. The physician should be warned of this, and should be on his guard against these pretended neurasthenics, who continually desire to remain in a recumbent posture and who always have on the table by their bedside bottles of wine and pieces of cold meats with which to fight their exhaustion. Great harm has been done to the minds,and bodies of the neuropaths by the fine theories of overfeeding. More often than is thought, their poor digestion, their fetid breath, their cutaneous and even their mental troubles are prolonged by a true alimentary intoxication, brought about by ill-understood advice. When bulimia is seen in its gross form, as in the case of Qe., the role which mental troubles play in these pathological cases of overfeeding is more easily recognized.
Observation 3. We now come to a still more singular case. This young woman, Ms., cannot be cared for in any sanatorium; she has hardly entered one when she is obliged to leave it because none of these institutions can place large enough grounds at her disposal. What can you expect? She must have exercise, and it is absolutely necessary for her to walk every day, without exception, forty or fifty kilometers on a public highway. The little garden of a sanatorium will not suffice, and the public highway with its kilometric posts which one can count is indispensable. It is only after having counted about forty-six kilometers that she begins to feel at her ease. Sometimes she has a carriage accompanying her, but she never enters it; she runs beside it while the horse is trotting. She hardly consents to stop for a moment to eat a morsel; she feels hungry, but that scarcely bothers her. She is more concerned by thirst, for she drinks enormous quantities, five to six liters a day, and she urinates accordingly. She starts again immediately, with an unconquerable need "to exhaust the superabundant energy of her nervous system"."
This mania for walking, a variety of the dromomania of Regis, seems very strange; it is, however, more common than is supposed. There are in Paris unfortunate persons who have a cement track built in their yards on which they walk during the hours when they cannot cover kilometers on the highway. In a more concealed form the same impulsion is now very often found in the mania of sports, which brutalizes so many neuropaths (ludomania of Eissié). Here also, as in the case of overfeeding, there is a danger of which the neurologist should be warned, and that is why he should think over those cases where the mania is as manifest as that of our patient.
Observation 4. Finally, I would like to cite with the preceding cases those patients who experience the desire of inflicting suffering upon themselves. In many of these cases it is only a question of small pains, of pinching, twitching, or scratching the skin, which seems to give them relief. Cha., a young woman twenty-four years of age, presents a curious appearance when she takes off, in our presence, her beautiful blonde wig. Upon her uncovered skull there are but a few rare locks of short hair, separated by large, absolutely bald spots, especially in front and on the occiput. At first sight one is convinced that it is a remarkable case of alopecia, and is astonished to learn that the dermatologists refuse to treat her and send her back to the neurologists. It is a fact that the hairs did not fall out by themselves. For the last eighteen months this poor girl has been tearing them out one by one and eating them. In this short period she has eaten up the whole of a luxuriant head of hair. This singular desire only comes at intervals to a girl who is otherwise quite rational and seemingly well balanced. But at moments she is no longer able to resist this desire to pull out her hair and feel the little pain resulting from it. This new case may be grouped with the patients I have already described who tear out their hair, their eyelashes, their nails, and little pieces of skin, etc.
Sometimes the impulsion to inflict injury on oneself becomes much more interesting when it is a question of severe pains.
Observation 5. This young girl of twenty, Ne., has her hands and feet covered with bandages, and looks more like one severely wounded than like a neuropath. Under the dressings there are a number of severe burns, some recent, with blisters, others suppurating, and others almost cicatrized. The parents of this young girl despair of curing her wounds, for scarcely is one on the road toward cure than a more severe one appears at its side. The young girl cannot stop herself from burning her hands and feet; her pleasure, when she is alone, consists in taking a kettle of boiling water, and pouring it, drop by drop, on the skin of her extremities. If she cannot find boiling water she satisfies herself by placing her fingers on the stove until the skin is badly burned. If we undress her we find on her thighs long circular cicatrices of a keloidal appearance. She had wound twine tightly about her thighs until her skin had been cut.
Before arriving at such torture she had merely tried to stop eating and drinking. She kept herself from evacuating her bowels or passing her urine for a very long time; for hours she kept her arms and legs in fatiguing and painful positions, etc. . . . Gradually, she has perfected these painful processes. We have here, you will say, an insane person who has a mystical delirium and who is anesthetic. By no means; she is a young girl, intelligent and instructed, who is not at all delirious, at least when she is being examined, and who has preserved all her sensibilities. She hides her face and weeps when her wounds are uncovered. She says she is ashamed to let any one see the absurdities which she has committed: "But what will you have? I did not think that it would be so serious, or that the marks would remain visible so long; I hoped that pain would be the only result. When I once let myself go I cannot stop myself. I am in great despair that my wounds cause so much trouble to my family. For their sake I would make the painful sacrifice of giving it up, but it so difficult to resist this desire of harming myself; it requires so-much courage for me not to give way to it." Exactly like a dipsomaniac, she takes all possible oaths, but no faith can be placed in them, and she must be watched, for in a few weeks she will begin again, first causing herself a little pain, then, as the appetite grows, she will not resist the pleasure of wounding herself severely.
These impulsions differ apparently in their aims; one relates to the desire for drink, the others to the desire for eating, to the need of walking indefinitely, or to a singular appetite for suffering; but yet they have common clinical characteristics: the periodic appearance of the desire; its irresistibility; the satisfaction following its accomplishment; the remorse of the subject, and his good but useless resolutions. There is certainly a psychological unity hidden in these diverse phenomena.
It is not difficult to see that these impulsions, differing so much from one another, have the same point of departure, and that they correspond to certain deep feelings quite the same in all the subjects. We must not believe in this illusory appearance which shows us the impulsions as primitive phenomena, appearing at the beginning of the attack. The patient deceives himself when he tells us that suddenly, without any reason, he is seized with the desire to drink, to walk, or to burn his feet. The observer can confidently state that in every case the impulsion is preceded by disease symptoms which are the essential part of the crisis. This is so true that in the following cases, we can with care foresee the return of the attack, and can place the patient on his guard against an impulsion which will not delay in coming, although he may not yet be conscious of the fact.
Our dipsomaniac, Dr. (Observation I), seems to be in very good health. She drinks water only, and can even look at a bottle of whisky on the table without the least desire to touch it. However, she is already troubled; physical or moral influences have already transformed her brain; now the change is produced during the menstrual period; now, following a simple cold; most often it is determined by her emotion on hearing bad news concerning the health of her husband, but it may sometimes follow an emotion caused by agreeable news. The patient reports at first without emphasis, then more and more forcibly, a general change in her feelings; it is like a veil of sadness spread over everything, a discouragement, a disgust for all action, a profound ennui which comes over her more and more. "Nothing interests me any longer, I am weary of everything, — to be interested in nothing is insupportable; it makes me nervous. Nothing is worth the trouble of an effort. I can no longer even get angry, for nothing is worth getting angry about, and I am astonished when I see people who have the courage to get angry. All things are well enough; the children are brought up well enough for what they have to do; the servants are satisfactory enough; everything in life is passable, and it is very wearisome. To be neither unhappy nor happy, to desire nothing, is very discouraging. You cannot imagine this feeling of a shadow which, little by little, invades the whole of life, like an eclipse of the sun."
The troubles of perception may even be accentuated; things may lose their reality and become like dreams; there are at moments feelings of false recognition, a feeling that the present is a part of past experience (déjà vu), agreeing well with the depression as I have often described it. The disturbances of the attention and of the will become enormous: "There is in my head a boiling mass of ideas, and in the midst of it all I do not know what to do or what to decide. I become hesitating, timid; I need to be guided, not to have to think of anything. I ask everybody's aid, and I obey nobody, for I no longer love those whom I used to love. What a horror it is to lose all feelings of affection! How do you expect me to be interested in a life which is no longer anything to me? If I continue thus a few hours longer I shall kill myself..." She need not kill herself because she begins to feel that there is another much simpler remedy within her reach.
Our second patient, Qe. (Observation 2), afflicted with bulimia, does not express herself so well, but she entertains the same thoughts on the days preceding her impulsion to eat. She is the daughter of an alcoholic. She herself is exhausted in consequence of infectious diseases and puberty. She frequently has attacks of depression, which she roughly explains by saying that she has sudden stomach trouble. She does not exactly suffer from that organ, but, in consequence of some emotion, "she has lost all strength to act; she feels herself weak, powerless, incapable of making a decision; she does not believe that she is in a real world; everything is a vague dream. At the same time, she is excited, anxious, and believes that she is going to fall into syncope. Her body might be said to be empty, not containing any nourishment." These feelings thus develop themselves during several days before she begins to eat in order to remedy this weakness.
The young woman, Ms. (Observation 3), has passed a comfortable evening following her unreasonable walk; she slept well during the night. But in the morning she wakes in an extremely painful state; she feels weary and depressed; her head feels tightly bound; her heart feels swollen. " My head is smothered; it is as if some one were pinching me, as though some one were pressing the top of my head; my ideas become confused, and I feel that I am going insane." This fear of insanity produces a state of anguish that continues until the patient yields to the temptation to seek the habitual remedy. This poor girl belongs, of course, to a neuropathic family; her grandmother was insane, her father very nervous. She, herself, had typhoid fever when seventeen years of age, and for a long time afterward remained weak and suffered from digestive disturbances accompanied by vomiting. She then had attacks of mental depression which, at the end of four or five years, were followed by the impulsions we are studying.
Cha. (Observation 4), who tears out her hair, presents the same feelings in a still more naive way. She is the daughter of an alcoholic, of low intelligence, and little activity. Brought up in the countiy, she barely learned to read. She was fit only for the rough work of the farm. Unfortunately she was sent to Paris as a servant. She claims to have had masters who were exacting and who scorned her. That is possible; but as a matter of fact, she was hardly capable of more delicate work than was asked of her. She became discouraged, homesick, complained of headaches and weakness. "She felt enfeebled, without life, without desire, without hope, seeking in vain for something to stir her, to relieve her."
The last patient, Ne. (Observation 5), with the mania for wounding herself, explains very well, even in her letters, this fundamental feeling of depression. For a number of years, ever since the beginning of puberty, she had been languid, weak, and dull, did scarcely any work, and dreaded any action or decision. " The further I go the more my mind weakens; the more complicated an act the more I. dread it. I stop before the least obstacle without knowing what to do. My parents, who see me do something from time to time, are deceived and think that I am really acting. What I appear to do is not done by me; it is done mechanically, as if it were done by some one else who had control of me. I prefer to do nothing at all, rather than feel within me these actions performed by another, which are as if inspired or forced by some one, God or devil [feeling of automatism and of domination]. It is too sad not to do anything of oneself; it is too humiliating. I am ashamed, too, afraid of being laughed at, and I prefer not to stir rather than act so. . . . I but half feel things; I am in a world which I do not understand, which does not exist, and which inspires me with a vague fear. . . . I can no longer speak to living beings; in the first place I do not know whether they are alive; and in the second I no longer belong to the same world with them; they humiliate me when they speak to me; I am going to withdraw into a corner where there is absolutely no one; I do not live, I cannot live, I do not wish to live. . . ."
These feelings of incompleteness are the same among the various patients in all these cases of impulsion; they are expressed in the same terms and by the same metaphors. In many cases it is easy to see that for a long time these feelings existed alone without any other moral trouble. Even to-day they plainly precede the impulsions, sometimes by several days. Consequently they seem to me to constitute the essential part of the psycholeptic crisis to which the impulsions are joined only as accidental phenomena.
I have already shown elsewhere, in a very typical observation, how the impulsions may be joined to the psycholeptic crisis in a somewhat accidental manner. D., a man of thirty, was subject, from the age of fifteen, to attacks of depression: "From time to time," says he, " it seems to me that I am giving way, that I am no longer good for anything, that I can no longer even read; everything appears strange and confused" ; and he adds, "This state is intolerable." For a long time, up to the age of twenty-two, he bore these painful attacks with resignation; thus crushed he remained, sometimes only for two hours, sometimes for several days. He even had a vague feeling that he required some sort of stimulation to pull himself together. "He would like to perform an eccentricity which would cause an emotion and pull him out of that condition." But in reality he does not do anything foolish, and the condition gradually disappears. Towards his twenty-second year he lived at a German university, and was drawn into excesses of drinking by his companions during these attacks of depression. These intoxications had a remarkable result, - that of raising his feelings from their profound depression so that a vague idea grew up in his head that intoxication was a sovereign remedy for his tortures. Since that time the nature of his attacks was changed, and when he feels depressed he is overcome by the obsessing and impulsive idea of drinking.
This is also what our first patient (Observation 1) very distinctly experiences: "What will you have? I am forced to perceive that whisky has a wonderful effect on my dark moods. After I have taken a drink of it everything changes color and becomes interesting again. I no longer feel stupid; I can see, read, speak, and act. It makes life more worth living; it gives a fictitious value to things. How can you expect me not to take it when I am on the point of killing myself out of despair and when I feel sure that it is only necessary for me to drink in order to change everything?"
It is the same with food (Observation 2) "which stirs one up, which makes one less timid; T would not be able to come to see you if I did not eat in the waiting room."
Exactly the same is true of physical exercise and of walking. When Ms. (Observation 3) has walked rapidly on the highway for some time she feels transformed. "Her head is cleared, her ideas come back, she is no longer distracted, she can talk, she is even able to work. Better still, she can now rest and sleep, while formerly she was not able to take any rest." Moreover, this last detail corresponds exactly with our observations; for sleep is more than one thinks, a difficult act, which requires a certain nervous tension for its execution. Over-fatigue, nervous depression, renders patients incapable of taking rest.
The same facts are observed among those curious subjects who experience the need of feeling pain. The patient who burns her hands and feet (Observation 5) has made a number of very clear observations concerning herself: "I feel that I make an effort when I hold my hands on the stove, when I pour boiling water on my feet; it is a violent act, and it awakens me; I feel that it is done by myself and not by another. . . . The means I use seem foolish, and I know that I abuse them; but what can you expect? Other people have the pleasure of doing things themselves; I desire to experience the same pleasure, and I cannot live without it. To make mental efforts alone is too difficult for me; I have to supplement them by physical efforts. I have not succeeded any other way, that is all: when I brace myself up to burn myself I make my mind freer, lighter, and more active for several days. Why do you speak of my desire for mortification? It is my parents who believe that, but it is absurd. It would be a mortification if it brought only suffering, but I enjoy this suffering; it gives me back my mind; it prevents my thoughts from stopping; what would not one do to attain such happiness?"
These are excellent psychological observations, which should be carefully considered by those who speak too lightly of asceticism without understanding the rdle which crises of mental depression play in mysticism. But we are not to study this question here: suffice it to say that the impulsions of all these patients have the same explanation. These absurd acts are sought for passionately, simply because they are exciting acts, and these individuals have an urgent need of excitation on account of the anguish which the mental depression produces.
If one pushes the question still further and asks why these acts should produce such great excitation in these patients, the answer seems to me very simple: It is not owing to the delirious convictions of these subjects, but it is because these acts are really exciting for everybody. Absorption of alcoholic drinks, ingestion of food, a walk in the open air, pain, or, rather, for this is the important thing, the fact of courageously bearing pain, - all these are very exciting things for every human being. This excitation can be observed at meals, in walks, in work, or in combats and acts of courage.
This fact can be verified even among patients who have no fixed idea on the subject. How many neurasthenics feel better after a meal, how many depressed persons are relieved by a walk, by exercise, or by massage! Even among melancholies, M. Dumas having no knowledge of this subject, has been able to demonstrate the favorable change of physiological and psychological functions under the influence of pain. Our obsessed have simply made correct psychological observations upon themselves; and have drawn the inferences from them. Still further to justify this interpretation, we can recall the large number of patients who, at first simply depressed, become dipsomaniacs, morphomaniacs, or erotomaniacs, in consequence of a fortuitous event which revealed to them a remedy of which they were ignorant. We may also lay stress upon those patients who have passed successively through several impulsions. Let us consider again the history of the case of Ms. (Observation 3), who has the impulsions to walk; five years ago she had exactly the same attacks of mental depression, but she treated them quite differently. She remained in bed and gorged herself with food continuously. She was thus subject to bulimia before becoming a dromomaniac.
I have in my notes an observation of an exactly opposite character. A young girl of twenty-two, who is now subject to boulimia, and who even hides pieces of meat in her bed to eat during the night, began by having impulsions urging her to violent exercises; she wished to run or to ride horseback the whole day. We cannot say that the disease has changed in either of these two patients; they have both remained the same, subject to painful psycholeptic crises with a profound and rapid fall of the mental level. They have simply changed the means with which they strove to combat that painful state. The origin of the impulsion is, therefore, outside of their ideas; it is in the depression and in the horrible feeling of death and of dementia which it inspires in the desperate effort which men instinctively make to recover life and reason.
It is none the less true that among the means employed by the patients are dangerous absurdities. The subjects fall into a double error. At first they imagine that a process, mildly stimulating when moderately used, will increase indefinitely in strength when employed excessively. It is the childish mistake of drunkards who think that a thousand drinks will produce a thousand times the gayety of a single one. The second error consists in imagining that there is but one way of being relieved. They forget that there are innumerable stimulating influences, and that change and novelty are indispensable in order to have their full effect. But these very errors are the results of the disease; the lazy minds of the subjects have a horror of change; they are incapable of having a new experience, of trying new methods. It is already a good deal if they are forced by external circumstances to understand the influence of walking and intoxication; they are not in a condition to make new discoveries by themselves. I have endeavored to show elsewhere that the obsession imposes itself unchangeably on the mind because it is an expression of a condition itself unchangeable. A free mind would have been able to find many other, often better, expressions, but the abulic mind is content with the expression once given, often furnished by chance, and is incapable of conceiving another one as long as the feelings of depression remain the same. The impulsion remains the same and does not vary because the subject is unable to conceive another remedy for a condition which does not change.
It is for us to introduce changes, and the understanding of the mechanism of the impulsions gives us the means of treating it. Let us not begin by declaring the means of the patient absurd. It is so far from being unreasonable that we ourselves make.use of it. To many of these patients we recommend nourishment, the use of certain stimulating substances, walking, gymnastics, and even a seeking after emotions. In many of these patients I strive myself to cause painful emotions; reproaches, threats, often have as good effects as do encouragements and caresses. I remember a young girl who felt well only if I had succeeded in making her cry during her visit to me. What we must explain to the patient or rather what we must make them feel, is that there is a host of exciting phenomena besides those they have chosen; it is above all necessary for them to understand the r61e of certain mental phenomena, such as the efforts of volition and attention, which, to their great surprise, are able to produce the same effects as a bottle of whisky. Finally, what is most important, we must not forget that the cause of the impulsion is, above all, in the underlying attack of depression; we must endeavor to discover, what is unfortunately not always possible, the physical or moral conditions that determine it; and we must, by all sorts of hygienic means, by proper mental treatment, prevent its reappearance. It can be easily seen that the therapeutic measures should be quite different in the cases where the impulsion depends on subconscious phenomena or suggestions, as is often the case among hysterics. It can be seen from this example that the psychological analysis of a pathological symptom is not only interesting from a scientific point of view, but that it can have practical application of the utmost importance.
There is a page on the website dedicated to abnormal psychology, which includes an important discussion on whether the term abnormal psychology is actually fit for purpose. See following link.
Sep 18, 19 08:00 AM
Wilhelm Wundt presented a landmark paper on the personal difference between visual and auditory observation at the Natural Science Conference at Speyer, Germany. Writing about Wundt's discipline defin…
Sep 17, 19 11:26 AM
Great article on the psychology of self-destructive behavior.
Sep 17, 19 08:00 AM
Oskar Pfungst began his famous investigation into the case of "Clever Hans," a horse that could seemingly solve mathematical problems (multiplication and division) by tapping out answers with his righ…