Popular Science Monthly/Volume 13/May 1878/The Scientific Study of Human Testimony I
|THE SCIENTIFIC STUDY OF HUMAN TESTIMONY.|
ABOUT two years ago I chanced to call on an educated professional man, who was much interested in the subject of delusions. He said, "I have been long wishing to see you, in order to get an explanation of some strange things that have happened under my observation." I inquired what these strange things were. He replied, as usual in such cases, by giving a detailed account of certain performances of a well-known trickster, to which I listened as politely as I could, and he concluded with this conundrum: "Now, how do you explain that?" I replied: "I do not know what happened, for there was no expert there to report. If I knew what happened, I could very likely explain it, for a knowledge of what happened would itself be the explanation." "But I have just told you what happened," he interposed, somewhat excitedly. "My wife and I both were there, and we saw it all, with our own eyes. Can't we trust our senses?" "Trust our senses?" I replied; "not at all. In science we never trust our senses." My friend was as much astonished and indignant as though he had been personally insulted, and I felt it to be prudent to withdraw from the house.
Quite recently, while conversing with a scholar and logician of far more than usual powers, we chanced to talk of the alleged feats of levitation, and he asked me how they were to be explained. I told him that there was no evidence that they had ever occurred; and that it was known deductively, by the established laws of physiology, that they had not and could not occur. I furthermore stated that claims of this sort could be and should be only studied by experts; that experiments with living human beings could only be conducted by experts in cerebro-physiology, and that probably there were not half a dozen persons in the world capable of making experiments of that kind. My friend failed to see the justness of this view, and confessed himself unable to understand how so simple a matter as the rising of a body in a room could not be settled by the eyes of any honest, well-balanced man. "Why," said he, "if a dozen George Washingtons should testify that they had all seen a man rise in the air, I should be compelled, by the rules of evidence, to believe them. What is the need of an expert in a matter of simple eyesight and common honesty?"
I refer to these conversational experiences, because they represent, in a concrete form, the present attitude of scholars and logicians toward the principles of evidence.
That these instances are not exceptional is proved by the literature of science, of religion, of logic, and of law, in all of which departments the subject of human testimony is more or less discussed. Neither in Whewell's "History of the Inductive Sciences" nor in Jevons's "Principles of Science" do we find a correct or thorough analysis of human testimony, on which all science depends; by these authors, as much as by religious, apologetic writers, it is assumed that the senses are to be trusted. In the department of logic we do not find, either in Mill or Hamilton, any attempt even to build up a science of human testimony which must everywhere constitute the premises of reasoning, and by which the results of reasoning are to be determined. Constantly Sir William Hamilton reiterates that logic deals only with the forms of reasoning, and is not at all responsible for the premises; but nowhere does he point out, in a satisfactory manner, the principles on which premises are to be obtained. It is true that Bacon, under the fantastic titles, "Idols of the Tribe," "Idols of the Den," "Idols of the Forum," and "Idols of the Theatre," first pointed out some of the more obvious sources of error, and writers on logic repeat his views; but other sources of error, equally important but far more subtile, are not referred to even in the most recent treatises on reasoning. Students of science, particularly of physiological science, and, above all, experimenters with living human beings, must either trust to their instincts, as many do, or find out for themselves, by study and experience, the special sources of error in researches of this character, and guard against them.
Coming to law, we find that Prof. Greenleaf, one of the most valued writers on the principles of evidence, says that "the credit due to the testimony of witnesses depends upon, firstly, their honesty; secondly, their ability; thirdly, their number and the consistency of their testimony; fourthly, the conformity of their testimony with experience; and, fifthly, the coincidence of their testimony with collateral circumstances." Here we observe that honesty is placed before ability, while under ability no distinction is drawn between general and special ability—in other words, between the non-expert and the expert. In the formulated statement of the principles of evidence from which this extract is taken, not only is there no distinction made between expert and non-expert, but no recognition of the fact that the senses of honest and unbiased witnesses may be, through a variety of causes, untrustworthy.
The mistakes in the administration of justice are already numerous, but they would have been more so if judges and juries had not instinctively rejected the principles of evidence thus taught by the highest authorities in jurisprudence.
All modern science is the product of exclusively expert evidence: until an expert develops, there can indeed be no science; and yet, one may look in vain through all the authors on logic for a satisfactory definition of an expert, or for any detailed arrangement of tests by which expertness is to be estimated.
The subject of human testimony has, in short, never been scientifically studied; practical rules for the guidance of those who employ it are all that either logic or law has yet given to the world. As some of these practical rules are based on incorrect assumptions in regard to the value of human testimony, they frequently lead to serious error, and, as they fail to draw just distinctions between the good and bad in evidence, or to give special suggestions for special cases, they are oftentimes of no assistance whatever. This criticism is not made in the way of complaint, for only within the past few years has it been possible to even begin the scientific study of human testimony, while nearly all of our writers on this subject belong to the past generations, and the few later authors mostly copy the errors and imperfections of their predecessors.
Human testimony comes from the human brain: the scientific study of human testimony is only possible through a knowledge of the human brain in health and disease, and is therefore a department of cerebro-physiology and pathology. Only recently have the laws of cerebro-physiology and pathology been sufficiently understood, even by the very few who cultivate that specialty, to enable them to formulate principles for the scientific study of that most important product of the human brain human—testimony. If, then, Bacon and Descartes, Hume and Hamilton, Whewell and Jevons, Greenleaf and Wharton, have failed to adapt their analyses of the principles of evidence to the needs of our time, their failure is due to the backwardness of physiology and pathology that must constitute the basis of the study of evidence, and on which the foundations for a reconstruction must be laid.
We do not yet know all of the human brain, either in health or disease; but our knowledge of it is sufficiently advanced to make it possible to see, with considerable clearness, its relation to testimony. If we do not know just how the cerebral cells evolve thought, we do know that thought is evolved by them or through them, and that various diseases of the brain and nervous system—now pretty well understood, but of which, twenty years ago, little or nothing was known—may utterly destroy the objective worth of thought, and render it, scientifically speaking, valueless.
The progress of cerebro-physiology and pathology, in recent times, has been mostly along the line of the Involuntary Life—a phrase which I have elsewhere and often used to designate those phenomena of mind or body, or of both, in their reciprocal relations, that are independent of will or consciousness, or of both. This Involuntary Life is the branch of physiology that has been least studied and least understood; its importance, however, is supreme, not only in itself, but on account of its relations to all other sciences. It is the one strategic point of modern thought, around which all the leaders in controversy are unconsciously gathering, and for the possession of which opposing hosts will soon contend. Here, as I have previously shown, is the last stand of modern delusions, of every name and form.
The scientific study of human testimony requires a recognition of these three facts, in the physiology and pathology of the brain:
1. The Limitations of the Human Brain in Health.—Literature is so crowded with laudations of the human intellect, from the classic apostrophe of Hamlet—"What a piece of work is man! how noble in reason! how infinite in faculty! in form and moving, how express and admirable! in action, how like an angel! in apprehension, how like a god!"—down to the motto of Sir William Hamilton: "On earth there is nothing great but man; in man is nothing great but mind;" and so strong is the tendency in man to view himself from one side only, and to compare himself with the lower animals, or even with inorganic matter, that we are scarcely prepared for the conclusion to which a scientific study of the subject compels us, that, considered from all points of view—from what is above and beyond it, as well as from what is below and near it, from the aspirations that can never be realized, the vast but simple problems of the universe that it hopelessly strives to solve, as well as from the narrow strip of territory it has subjected to science—the human brain is an organ of very limited capacity.
If some superior being endowed with superhuman, though not necessarily divine powers, should attempt to analyze the mind of man—to assign its relative position in creation, and to place it, properly ticketed and labeled, in some supra-terrestrial museum—it would be found to be a far less imposing object than man's own imagination has pictured it. If it be claimed, as it may be by some, that although this brain has thus far achieved but little, although, whether considered in the aggregate, the average capacity in many nations and through many generations, or, concretely in cases of individual and exceptional genius—as Socrates, Napoleon, Goethe, Newton, Shakespeare—it has fallen so far short of its desires and aims and apparent needs as not to merit the encomiums that poets and philosophers have lavished upon it, yet it has before it in this world, and in our present mode of being, a future of possibly infinite development, I may reply that the study of human testimony is in no way affected by such possibility, since it has to do only with the brain in the past, the present, or the near future.
The whole subject of the limitations of the human brain" is of high import, is very wide in extent, and suggestive practically as well scientifically and in ways almost innumerable, some of which I hope to point out at a future time; but, for the present purpose, the reconstruction of the principles of evidence, it is necessary to refer only to the following illustrations:
1. The fact that success, even with the most richly-endowed natures, is only possible through specialism.
2. The imperfections and uncertainties of memory.
3. The exceedingly narrow limitations of the senses.
4. The fact that the best results of cerebral activity are largely involuntary, if not unconscious.
Specialism is not peculiar, as some would believe, to modern science or recent civilization; all the famous Greeks were specialists: one could not conceive of a Socrates, Homer, Phidias, Pericles, Demosthenes, and Sophocles, combined in a single individual. Although poetry and philosophy, being nearly allied, have been the twin products of one superlatively endowed intellect—although Goethe has demonstrated the possibility of uniting the genius of song with the genius of speculative science—yet no human being as yet proved himself at once great in poetry and mathematics. The combination of a Newton and Milton seems impossible; a conclusive and crushing deductive argument against the theory of the Baconian origin of Shakespeare's plays is, that no single brain could have produced the "Novum Organum" and "Hamlet."
In the present century, science has become so specialized that all the advances are made by specialists in comparatively restricted fields, by men whose entire energies are concentrated for a lifetime in some single path of research beyond which they never wander, and in which alone they are accepted as guides. So universal is this law of specialism that the instincts of men regard with suspicion any one who attempts to become an authority on more than one branch of science, while literature is so split up into divisions and subdivisions that eminence in all is unattainable. The lopping away of all superfluous branches, that bearing boughs may live, is carried to such an extreme that only one branch remains, and through this the whole cerebral force circulates. The human mind is like a stream which carries along the same amount of water, whether it flows through one channel or many. In spite of all the criticisms of specialism and specialists, the work of specialization has gone on, and in obedience to the law of evolution must yet go on; specialists are our sole authorities, even among those who despise them:
science and specialism are identical; not to specialize is to lose the prizes of life. Germany, which in philosophy and science does the original thinking of the world, is, as we all know, a nation of specialists.
There are, it is true, degrees of specialism, and the term is largely a relative one: in medicine, where the word is mostly used, and where until recently it has been a term of more or less reproach, all general practitioners are really specialists, since medicine and surgery are both offshoots from the professions of the priest and the barber; in biology, some are authorities only on paleontology, others on natural history in general, others on some special branch, as entomology, others still on some one insect, as the bee; and this subdivision is continually going on with the evolution of systematized knowledge. These statements may be truisms to students of sociology, but they are truisms that are forgotten by all the writers on testimony, although, as we shall see, they lie at the root of the reconstruction of the principles of evidence.
Equally important in its bearings on the scientific study of testimony is the recognition of the fact that memory is far more untrustworthy than has been commonly supposed. But a very small fraction of the impressions made on the cerebrum are so far retained as ever to be called up at will. Theoretically, the brain is like a target on which every idea that is evolved makes a permanent impression which no subsequent impressions can thoroughly destroy; practically, it is rather like a series of sieves by which thoughts are sifted through various stages below and on the borders of consciousness and recollection, while only the coarser and larger grains are retained where they can be used when needed. Under the stress of special excitements—as in the terror of drowning or protracted falling, or in trance, impressions long forgotten are revived and rise to temporary consciousness, so that men suppose that the panorama of all their past lives is passing before them; but, even under such exceptional crises, it is certain that only a comparatively few of our mental impressions actually reappear; some long-forgotten events arise with vivid distinctness, and the startled subject believes that all his life is let loose.
Nearly all the acquisitions and experiences of life are forgotten, even by the best memories; only the tiniest trifle of past events or past knowledge can ever be recalled. How dreams are forgotten we all know, but the difference between the recollection of sleeping and waking thoughts is only one of degree; by the standard of memory, all life is a dream. The pleasant experiences of infancy and early childhood, which, if they could be recalled at will, would so enrich and glorify human existence, are to us as though they had never been; as maturity appears, childhood dies.
Children really, as compared with adults, have very poor memories; they forget almost everything; even in infancy the experiences of each year are wiped out by the experiences of the succeeding year; bright babies pass through a succession of hobbies in their various games and sports, and methods of speech and conduct, likes and repulsions, and so forth, which are successively and almost completely forgotten. The whole process of education, public and private, is based throughout on the imperfections and uncertainties of memory. If it were possible for youths to retain what they read, or hear, or see, our schools and colleges might be closed, or, at least, remain open but one month in a year. With children, as with adults, life is but a series of unrememberable experiences; to live is to forget.
All boasted human learning is a temporary treasure, a loan rather than a permanent gift, which must be watched and tended every moment lest it slip from our possession. Truly has it been said that scholarship consists not in knowledge but in knowing where knowledge can be found: he is the learned man who knows not the contents of books but what the best books in any specialty are. School and academy and university graduates, who after years of active and it may be eminent professional life look over the examination-papers of alma mater and the catechisms of their childhood, find invariably that outside of the special lines of their lives they are unable to answer correctly and with certainty the simplest questions, and must conclude that all the wisdom of the world is with sophomores and school-children. Even special departments are, through the limitations of human capacity, so minutely specialized that one soon despairs of remembering anything more than what belongs to the daily routine in the pursuit of a specialty; an original author in science must continually refer to the books he has written, lest he forget his own discoveries.
Some experiments that I have made with the memory, the full details of which are to be published elsewhere, give results that are of the highest significance in their bearings on the study of human testimony. These experiments were modeled in part on the familiar "Russian game," so called, which is sometimes practised by the young as an amusement, and which consists in telling some short story to a party, who at once repeats it, or all that he remembers, or thinks he remembers, to another party, and so on through a series of half a dozen or more individuals. In order to make the experiment a fair one, and of value in the study of memory, the story designed as a test should be short and simple, and should be written out and clearly stated to the individual who stands second in the series. The second individual takes a third individual into another room, writes out the story from his recollection and reads it, the third party does the same by the fourth, and so on. When all the stories are compared, at the close of the experiment, this general result is invariably reached:
1. No two of the stories agree. All have departed more or less widely not only from the original, but from the account which they themselves directly received from the person next to them in the series. No one has succeeded in remembering just what his neighbor told him, although he wrote down instantly what he heard.
2. In some of the stories interpolations occur, as well as omissions. These additions are sometimes of an important nature, seriously modifying the thought of the original, and, what is more strange is, that these are frequently believed by the authors to be parts of the original; they are sure that they have given only what was given to them, and are astonished and incredulous when a comparison is made between the original and the others in the series. Not only the phraseology but the thought is changed.
Another method of experimenting with the memory is, to repeat the same story to a number of individuals separately, and then, after all have written out by themselves without conference what they can remember, to compare the results.
Experiments of this kind, it will be observed, are made under every conceivable advantage: there is no haste; there is no excitement, at least after the novelty is over; there are no distractions; the power of recollection of words and facts is at its best. The accounts are written down instantly as they are received; they are consequently the virgin impressions on the brain. I have made these experiments with intelligent, liberally-educated persons of both sexes, and have repeated them sufficiently often to demonstrate that the results noted here are laws and not exceptions; and it is as clear as any fact in science can be, that works like Boswell’s "Life of Johnson," and Goethe's conversations with Eckermann, and Luther's "Table-Talk," and indeed all conversational literature, must be regarded as representing the tendencies of the heroes of the conversations, the general drift of their uttered thought, rather than the precise language employed, or the order in which the statements were made. Certain phrases often repeated by an eminent man in the presence of his friend may be in some instances literally transcribed, especially if they are of an original and striking character; but exact details of long conversations are never recalled—except perhaps by certain prodigies of whom I shall presently speak. Interviewing reporters are sometimes unjustly censured for intentionally interpolating errors in their published statements. The day following an interview, or even five minutes after, neither party can tell precisely what has been said, although sufficient may be remembered for practical needs. Conversation can only be accurately reported when it is taken down at once as the words are uttered. Conversations reported weeks, months, and years, after their occurrence, must be not only wide, but very wide, of the facts; and, besides the positive omissions, there must be, in all cases, interpolations or additions both of fact and of language which the author is confident, and very likely has all along been confident, that he received from the original. The subjective is confounded with the objective, and there is no way by which they can be distinguished.
These experiments bear directly and obviously on history and on legal testimony, they show the hollowness of much of what is called historic evidence, and the uselessness of the attempt so often made in court to force or coax witnesses to give the exact language used by them, or to them, or in their presence. I once told a short story to a person who has the most remarkable memory both for words and facts of any one whom I have ever met, and requested him to at once repeat it. He attempted to do so, and not only changed the phraseology, but left out one of the most important details. In some cases I have requested the subjects experimented on to wait a week or ten days, and then to write out what they remember, or think they remember, of what was told them. In all cases there will be variations from the original of greater or less importance, according to the nature and complications of the story, and the special memory of the individual. One person, a scholar of unusual verbal memory, after carefully studying a short story, consisting of less than one hundred words, and waiting ten days, made eight blunders.
In elaborately comparing the recitations of experienced and eminent actors and actresses with the originals of plays, I find that serious verbal changes, both of omission and interpolation, are constantly made. Dramatic teachers say that pupils cannot accurately retain a long part; that blundering is everywhere the rule. Shakespeare, in his choicest passages, is almost always, unintentionally if not unconsciously, altered even by his most skilled and practised interpreters.
The statement made by Renan in his latest work, on "The Origins of Christianity," that persons who do not know how to read and write have a better memory for oral communications, is not confirmed by my experiments thus far; scholars and thinkers remember words and ideas better than the ignorant and unreading classes. Those who do not know how to read and write find it hard, according to my experiments, to retain in memory a short and simple sentence, even for an instant. Not only memory of words, but of facts and objects of common observation, is more limited than is supposed.
In another series of experiments I tested the power of recalling the objects that fell upon the vision. If a number of persons enter a room containing a number of articles of furniture, with various colors on the walls and in the carpet, and in which certain complex gestures or motions or manoœvres are made by some one, there will be no agreement in their reports, even if made at once, and no report will be accurate.
For years philosophers and critics have been asking how long time is required to make a myth. The answer is found in these experiments. A myth can be made in a minute. These interpolations and additions to reported conversations, of the truth of which the reporter, at the time and subsequently, is so fully persuaded, that only by a comparison with the written original can he be undeceived, are the products of the reporter's own mind—the unconscious substitution of the subjective for the objective words and phrases and thoughts of his own brain, which, perhaps, have long been parts of his mental possessions, rise up like ghosts in the midst of his narration, throw aside the original words and phrases and thoughts, and take their places so perfectly and so harmoniously that the intrusion is not suspected.
It may be said—indeed, it is often said—that memory is a distinct and narrow faculty, in no way correlated to other and more important faculties, and that its perfectness or imperfectness has little relation to the cerebral force. Even if this view of the nature of memory were the correct one, it would not invalidate what is here claimed of the relation of memory to human testimony. But this theory of the nature and office of memory is not the correct one; it is opposed to all that is known of the brain and of its functions, whether studied physiologically or psychologically. Memory is simply a register of a small fraction of the impressions made on the brain; there are, therefore, as many different kinds of memory as there are different faculties or combinations of faculties. Memory is a measure of mind; but, as there are as many varieties of memory as there are varieties of talents in man, the memory of any man can only measure the talent peculiar to himself. We remember what we have a capacity to comprehend. Any man, it has been said, is willing to admit that his memory is poor, but no one will admit that his judgment is poor; and yet judgment is largely the result of memory. One may have a good judgment in some departments, but a very poor judgment in other departments; but, in those departments in which the judgment is good, the memory must also be good.
The relation of memory to mind is illustrated, if not demonstrated, in the early and late history of infant prodigies, such as blind Tom the musician, Colburn the mathematician, and the famous "boy orator." An analysis of the mental powers of any of these prodigies brings out these four facts common to them all: 1. Extraordinary memory in some one department; 2. Correspondingly extraordinary genius in that department; 3. Marked and unusual deficiency of other mental qualities, amounting in some instances to idiocy; 4. Decline of their special gifts corresponding to the development of other faculties on reaching maturity. "In monstrosities Nature reveals her secrets;" the physiology of mind, the general relation of mind to brain, and the relation of memory to mind, can all be studied effectively through infant prodigies. In no class of beings are the limitations of the human brain so thoroughly demonstrated as in these very prodigies that are supposed to illustrate in a marvelous way the capacities of intellect: all their special endowments are bestowed at the price of general endowments; the ordinary is sacrificed to the extraordinary. If they ever mature and become well-balanced citizens, the particular genius that made their childhood famous must correspondingly suffer. Even the average child, as we have seen, loses its memory in certain directions as it advances to maturity; hence the common but erroneous belief that the memory of children is better than the memory of adults. In truth, average children remember far less in quantity than adults, and they remember different things according to their age and taste. With children as with adults, and as with prodigies, the memory, scientifically studied, is an exact measure of mind, and in all, old and young, its limitations are so great as to impair most seriously the value of most of human testimony, even in matters of every-day life; while in all science, or the capacity of the human brain for observing systematized knowledge, for thinking and for remembering, is so limited that the world must defend, and practically, in the face of all the teachings of logicians and authorities on evidence, does defend, and rests its faith exclusively on, the testimony of experts, and in claims of new discoveries, especially against antecedent probability, on the testimony of a few only, and those of the very highest character—experts of experts—the opposing testimony of millions and millions of non-experts, though concurring and including the best and wisest of mankind, through all the ages being justly regarded as worse than worthless.
- It may perhaps be objected to this statement that many so-called apologetic and skeptical writings are of recent date; but writers of this class, on both sides, as well as the controversialists on the spiritualism question, assume, without discussion, the principles of evidence as taught in logical and legal text-books. On every page of the writings of the Tübingen school, as De Wette, Bauer, Paulus, Straus, as well as of their opponents in Germany and in the Bampton Lectures, we find evidences of the imperative need of a reconstruction of the principles of evidence. This need is fully admitted by the late Mr. Mozley, in the preface to the third edition of his "Lectures on Miracles."
- "The Scientific Basis of Delusions; or, a New Theory of Trance," etc., 1877.
- The number of distinct thoughts of which the mind is capable in a given time is very limited, and can be estimated by experiment with considerable precision. Says Sir Henry Holland:
"Within a minute I have been able to coerce mind, so to speak, into more than a dozen acts or states of thought so incongruous that no natural association could possibly bring them into succession. In illustration I note here certain objects which, with a watch before me, I have just succeeded in compressing, distinctly and successively, within thirty seconds of time—the Pyramids of Gizeh, the ornithorhynchus, Julius Cæsar, the Ottawa Falls, the rings of Saturn, the Apollo Belvedere. This is an experiment I have often made on myself, and with the same general result. It would be hard to name or describe the operation of mind by which these successive objects have been thus suddenly evoked and dismissed. There is the volition to change; but how must we define that effort by which the mind, without any principle of selection or association, can grasp so rapidly a succession of images thus incongruous, drawn seemingly at random from past thought and memories? I call it an effort because it is felt as such, and cannot be long continued without fatigue.
In commenting upon this a writer in Nature says: 'This is a curious subject which easily admits of experiment, but it will be found that the velocity with which thoughts can be made to succeed each other depends entirely upon the degree of similarity or connection between them. Judging from my own experience and that of three students well qualified to test the matter, I find that, where the objects thought of are as incongruous as possible, the number which the mind can suggest to itself in a minute varies from twelve, the result of Sir Henry Holland, up to about twenty. Any one who tries the experiment, however, will find that there is an almost insuperable temptation to go off on lines of association. To avoid these, and yet to think rapidly, requires a very disagreeable effort, becoming more and more painful by repetition. When the thoughts are restricted within certain grooves, as it were, the result is more rapid succession. Thus one student was able to think in a minute of thirty different kinds of actions, forty-six animals, fifty places or fifty persons. I can myself think, without much effort, of thirty-two animals or forty places or persons, in a minute. Even in these cases, however, it will be found that the rapidity greatly depends upon the degree in which the objects have been associated. When thoughts have been very closely and frequently linked together, the number of which may be compressed within a minute is much greater. I find that I can count about ninety-six in half a minute, which, without allowing for the two places of figures, gives one hundred and ninety-two thoughts per minute. I can think of every letter in the alphabet in five seconds at most, which is at the rate of more than three hundred per minute. Finally, by counting the first ten numbers over and over again, I have compressed nearly four hundred changes of idea within the minute.' "