Part 11

In the first place, what do we mean by the initial credibility of an event? There are very few cases where this notion can be precisely defined. The simple instances dealt with in the elements of mathematical probability do, it is true, permit of precise definition. The chance that a white ball will be drawn from an urn containing five black balls and one white ball can be exactly estimated, for we are in possession of all the very simple relevant factors. But the probability that Romulus founded Rome obviously belongs to a very different category. And what is the initial credibility of a miracle? Hume, as is well known, thought that the _a priori_ incredibility of a miracle was so great that its occurrence could not be established by human testimony. He is here trying to establish a ratio between the initial credibility of a class of events and the initial credibility of human testimony to such events. He is taking some kind of average in both cases, but it is difficult to see how such an average can be arrived at. Vague considerations of this kind are of no value in forming conclusions on matters of real interest to us, although they may be sufficient to warrant a lazy scepticism regarding what William James calls “dead hypotheses,” or may form the basis for amusing and ingenious mathematical exercises. But we have no notion of an average initial credibility which is of any use in practice; each case must be judged on its own merits. And if, to take the second point, we reached some average for the value of human testimony in general, we should never, in practice, apply it. The utmost we can hope to do is to establish a more or less constant relation between the testimony of classes of witnesses and classes of events. We have to divide witnesses into types, and for each given type estimate the value of its testimony to different classes of events. We must investigate the difference it makes when the witness is taken as isolated and when he is taken as a member of a group of witnesses. In this way we may hope to reach results which are of value in judicial procedure, in the study of history, and in various particular investigations, including those modern substitutes for miracles, the phenomena of spiritualism. We are, in fact, to investigate man in his capacity as a truth-recording instrument.

The result of such researches as have been made may be said, briefly, to show that human testimony has much less value than is normally assigned to it and, in particular, much less value than it is held to possess in a Court of Law. The experimental results obtained in this field are, indeed, often startling. It is hardly too much to say that one’s first impulse, on becoming acquainted with the results hitherto reached, is to fall back on a general and dismayed scepticism regarding the value of human testimony to anything whatever. But a closer examination of the results show us that this attitude is unwarranted, and reinforces the common-sense assumption that the value of human testimony is a matter of degree, varying from complete worthlessness to a very fair presumption that the event occurred as stated. The investigation is useful chiefly in showing us what factors influence this value.

It is convenient to separate out these factors according to the scheme recently employed by Dr. Edmond Locard, in his analysis of police records over a number of years. The statements made by a witness repose, in the first place, on sensations which he has experienced. It might be thought too obvious to be worth mentioning that we require the witness who heard a sound, for instance, to have reasonably good hearing, and yet there are many cases where simple preliminary considerations of this kind are not taken into account. Professor Zöllner’s famous book _Transcendental Physics_, for instance, alleged marvels that occurred in the presence of Slade, the medium; and these alleged marvels, of great influence in spreading a belief in spiritualism, were witnessed to by four professors, Zöllner, Fechner, Scheibner and Weber. But a member of the Seybert Commission, Mr. George S. Fullerton, as a result of personal interviews, found that two of these professors, Fechner and Scheibner, were partially blind at the time. Their sensations, therefore, in this respect, were untrustworthy. But defects of this kind may usually be determined and this factor conditioning the witnesses’ credibility allowed for. Where a witness makes appeal to a sensation which may be checked the check should always be imposed. Thus Dr. Locard gives an instance where a witness stated that an event occurred in a mill at a certain hour. How did he know the hour? By hearing a clock strike at the time the event occurred. A test was made, and it was found that the noise of the mill made the striking of the clock quite inaudible. The witness then remembered that he did not hear the clock strike until he had left the mill. Similarly, witnesses have testified that they saw a man leave a doorway, their post of observation being one from which the doorway could not be seen. Sensations may often be checked, however, and, to a careful inquirer, they need not be a grave source of error. But the next stage is concerned with the witness’s perceptions. Of his sensations he will single some out for attention and neglect the rest. He singles out those which, for some reason or another, interest him most. It may quite easily happen, therefore, that the sensations most relevant to the inquiry in hand have been neglected. They have been filtered, as it were, through the medium of the witness’s interest; and it is often the case that his interest has not been excited by the sensations most pertinent to the subsequent inquiry. It is on this fact that conjurers very largely depend for their success. The attention of the audience is distracted; they are invited to dismiss certain sensations as being of no importance, and, in general, it is remarkably easy to ensure this distraction of attention. Dr. Hodgson’s case of the English officer and the Hindu juggler well illustrates this point:

Referring to the movements of the coins, he said that he had taken a coin from his own pocket and placed it on the ground himself, yet that this coin had indulged in the same freaks as the other coins. His wife ventured to suggest that the juggler had taken the coin and placed it on the ground, but the officer was emphatic in repeating his statement, and appealed to me for confirmation. He was, however, mistaken. I had watched the transaction with special curiosity, as I knew what was necessary for the performance of the trick. The officer had apparently intended to place the coin upon the ground himself, but as he was doing so the juggler leant slightly forward, dexterously and in a most unobtrusive manner received the coin from the fingers of the officer, as the latter was stooping down, and laid it close to the others. If the juggler had not thus taken the coin, but had allowed the officer himself to place it on the ground, the trick, as actually performed, would have been frustrated.

Now I think it highly improbable that the movement of the juggler entirely escaped the perception of the officer; highly improbable, that is to say, that the officer was absolutely unaware of the juggler’s action at the moment of its happening; but I suppose that, although an impression was made on his consciousness, it was so slight as to be speedily effaced by the officer’s _imagination_ of himself as stooping and placing the coin upon the ground.

We have here an instance of erroneous testimony by a witness to his own actions; testimony to the actions of other people is usually much less trustworthy. In this matter of direct perception we may discriminate still further. Tactile perceptions are of almost no value whatever. If a witness be blindfolded and asked to determine, by touch alone, the nature, the volume and the material of an object, it will be found that the responses are very inaccurate. Experience of tactile sensations is relatively small and deductions therefrom are practically valueless. Thus the shock of a bullet entering the body may be interpreted as a slight blow, several dagger thrusts in the back as one thrust, and so on. A piece of ice drawn across the neck of a blindfolded man and warm water simultaneously poured on his chest have been stated to cause death by fright, the man having previously been informed that he was going to have his throat cut. Perceptions of odour or of taste are even less trustworthy; and here the difficulty of expression in precise terms, in the lack of a precise vocabulary, is complicated by the fact that the witness primarily perceives odours and tastes as pleasant or unpleasant, and pays attention only to that aspect of them. In cases of poisoning, therefore, evidence of this kind should be given very little value.

It is only when we come to the senses of hearing and of sight that we enter the region where perceptions may have evidential value. In the case of hearing, however, we must still proceed very warily. Experiment has shown that estimates of direction, for example, are quite valueless, since the different estimates made by different observers obey the laws of pure chance. Training can do a little, but very little, to render these perceptions more trustworthy; in general, however, evidence as to the direction of a sound may be neglected. Estimates of the distance of a sound, also, are of very small value. The intensity of a heard sound depends on the intensity of the source, and also on its distance; and these two factors may be apportioned by the observer in the most arbitrary manner. In the case where the sound is articulate, as in overhearing a conversation, we are in the presence of still other sources of error, due to illegitimate inference and the association of ideas. For words which are not heard will be supplied by the witness in all good faith. He will have a theory of the purport of the conversation, and will arrange the sounds he heard to fit it. Edgar Allen Poe’s example, in _The Murders in the Rue Morgue_, of the cries of an ape which were interpreted as remarks in different languages by different observers, is judged by Dr. Locard to be not at all fantastic. The same general source of error applies to visual perceptions. Not everything is observed, and the lacunæ are filled in by the witness in what seems to him the most probable manner. Oversights in proof-reading furnish a familiar example of this kind of error. But psychological experiments have produced much more striking examples. Claparède arranged for a man, wearing the mask of a clown, to enter his lecture room while a lecture was in progress. The students were afterwards asked to pick out this mask from a series of ten, and out of twenty-three who attempted the task five only were successful--and even these successes were probably due, largely or wholly, to chance. The appreciation of distances, measured by the eye, is also very likely to be erroneous, the rule being that large distances are under-estimated and small ones over-estimated. A similar rule holds good of estimations of intervals of time. Errors of this kind are not pure errors of perception; they are due chiefly to lack of experience. A carpenter or builder would usually make a much more accurate estimate of the dimensions of, say, the side of a house than would the ordinary person; and astronomers who work with transit instruments have, as a class, very accurate perceptions of small intervals of time. It is chiefly lack of experience, also, which is responsible for the absurdly different estimates different observers will make of the number of people in a crowd. Dr. Locard states that, on questioning the policemen employed to keep order during a procession as to the number of people they estimated to be taking part in the procession, he obtained the figures five thousand, ten thousand, twenty-four thousand. The actual number, he states, was three thousand. And during another procession two middle-aged, intelligent, educated Paris journalists gave as their estimates for the number of people engaged, the one thirty thousand and the other three hundred thousand.

But now let us suppose that our witness, through the medium of his imperfect senses and his partial attention, has received a certain image. What deformations may it suffer before it is produced as his evidence? If his memory of the incident has “lapsed” the image will undergo comparatively little alteration, but if it has often been called to mind it will probably suffer a very considerable change. Each time the image is recalled it will suggest others; the creative imagination gets to work, altering the emphasis, adding particulars, obliterating others, and the result will be as much a work of art as the reproduction of a fact. This tendency is particularly to be noticed with women, and with certain “excitable” types; it may be almost a national characteristic, as with Gascons and Sicilians. But all witnesses are prone to this kind of inaccuracy. Where the event has often been narrated by the witness the deformations become even more serious. For he is here exposed not only to the suggestions of his own creative imagination, but to the suggestions of other people. Every one wishes to make a success of the story he is telling, and the perception of what points to stress and what details to add is wonderfully ready and alert. It has often happened that a witness of perfect good faith has changed from the simple spectator of a drama to a prominent actor in it under the influence of repeated narration. Finally, we reach the point when the witness has to bear his formal testimony. His observations were imperfect, he has imperfectly remembered them, his imagination has distorted them, and he is now to express them. A very considerable additional source of inaccuracy is likely to enter here. The witness probably cannot express his complete image--words may not be sufficiently precise to render the fine shades of his remembered perceptions. The nature of a sound, the kind of emotion expressed by a voice,--he may have no words for such things. And, in any case, the witness will not express his complete image. He will select--in accordance with his own estimate of what is pertinent and what trivial. He will do this even if he be allowed to talk to his heart’s content; but the method of question and answer as pursued in our Law Courts leads to even more imperfect expression. For he is forced to be precise where his recollection is vague, and he will either give a false precision to his answer or else profess complete ignorance. More often still the witness sins by exaggeration, and these exaggerations, in a thousand subtle ways, usually tend to add to his own importance. And it is important to notice that, besides tending to import fictitious details, the witness will tend to exaggerate his degree of conviction. Where he was originally doubtful he is now perfectly sure.

So far we have been considering the witness in isolation, and we have not considered the reaction upon his testimony of the emotional state produced in him by the event. Yet the emotions accompanying the event have a great bearing upon the value of the witness’s testimony. During the war it was noticed that the evidence of soldiers freshly wounded was often of the most fantastic description. They would testify to the details of catastrophes which had never occurred; they would assert that so-and-so had been decapitated in front of their eyes, and so-and-so buried by an explosion, when, as a matter of fact, nothing remotely resembling these events had taken place. And, under the influence of the comparatively slighter emotions of a spiritualistic séance, people will identify the same “materialised” mask as the features of their husbands, wives, sons, daughters. Under the influence of such emotions it may be taken as a general rule that perceptions deteriorate, and illegitimate inference, “unconscious reasoning,” becomes more marked. Unconscious reasoning, indeed, plays a very great part in nearly all cases of mal-observation. It is well exemplified in the statement of the man sitting in a dark wood: “That dog’s bark is not really a grasshopper, it is the squeaking of a cart.” And Dr. Locard tells of one experiment he made, while in the Army, with a barometer which bore a remote resemblance to a clock. His suggestion that it was a clock was invariably accepted, even by the most eminent people, and several of them acquired their knowledge of the time of day from its indications, even when the hour so indicated was highly improbable. The testimony of great and commanding figures, even to the time of day, may therefore be open to suspicion. But the immense part played by unconscious reasoning is best seen in the psychology of conjuring, under which head it is fair to group the great majority of alleged spiritualistic phenomena. In this latter case we have further to recognise what Freud calls the “pleasure-pain principle,” as distinguished from the “reality-principle.” In other words, the witnesses are seldom disinterested; they strongly desire to witness certain events rather than others, and in such cases the slightest suggestion is sufficient to produce conviction.

When the witness is not isolated, but is a member of a group, the defects we have before noted, due to the creative imagination, are likely to be accentuated. The event will have been discussed and a uniform version gradually prepared. It is almost impossible, from the unanimous testimony of a number of witnesses who have been in consultation, to extract the original perceptions. The phenomenon of _mimétisme testimonial_ makes its appearance, and may assume abnormal dimensions. A kind of collective hysteria may be induced, and there can be little doubt that some of the collective denunciations of witches which took place in the Middle Ages were manifestations of this form of mimicry.

Such are some of the results that have been reached by the modern investigations of the value of human testimony. They tell us little we did not know before, for mankind has had an immense experience of human testimony; but they make our knowledge more precise and enable us to see what kinds of testimony are most open to suspicion. The effect of these researches on judicial procedure should be considerable, and their influence on the study of history not less marked. On this latter subject their influence can only be indirect, and in the direction, probably, of throwing still more doubt on the accuracy of historical records. The “credibility” of a witness still remains a vague quantity, but the chances are that it is something less than the value hitherto assigned to it. The investigation can claim no such precise results as those enunciated by Craig in 1699 in his _Theologiæ Christianæ Principia mathematica_, where, after proving that the suspicions of any history vary in the duplicate ratio of the times taken from the beginning of the history, he shows that faith in the Gospel, so far as it depended on oral tradition, expired about the year 880, and, so far as it depended on written tradition, would expire in the year 3150. The new investigations of the value of human testimony start from humbler, but surer, foundations.

_Printed in Great Britain by_ Butler & Tanner, _Frome and London_

=TRANSCRIBER’S NOTES=

Simple typographical errors have been silently corrected; unbalanced quotation marks were remedied when the change was obvious, and otherwise left unbalanced.

Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in the original book; otherwise they were not changed.