Popular Science Monthly/Volume 41/October 1892/Language and Brain Disease
|LANGUAGE AND BRAIN DISEASE.|
By HOWELL T. PERSHING, M. Sc., M. D.
NOTWITHSTANDING the great number of persons engaged in learning and teaching languages, there is no general agreement as to what is the best method that can be employed. Indeed, there seems to be no belief that there can be one method which is best for both modern and ancient languages, for the pupil who must learn to converse and for him who wishes only to read. Nevertheless, there are well-ascertained facts concerning the brain, which point unmistakably to one method as the best. Hence, I have ventured to believe that all engaged in linguistic work would find it interesting and profitable to consider these facts, which, though far outside the linguist's usual field, are capable of throwing a strong light upon his work.
All the motions and sensations of the various parts of the body are represented on the surface of the brain as on a map. Thus, there is a separate brain area necessary for sight, another for hearing, another for the motions of the fingers, and so on. Each of these areas is called a center. Four of these are especially concerned in the use of language, and may therefore be called language centers: the auditory center, by which words are heard; the motor speech center, which excites and controls the vocal organs in speaking; the visual center, by which written words are seen; and the writing center, which guides the motions of the hand in writing. These centers are capable of individual development by practice, and, in order that each one may receive its due share of cultivation, it is necessary to know its relative importance in the different ways of using language.
Disease instructs us on this point by making some interesting though ruthless experiments. Inflammation, or the growth of a tumor, or the rupture or plugging of a blood-vessel, may destroy any of these centers, involving, of course, a loss of the corresponding function. Consequently, the various defects in the use of language are the subject of a large and very important chapter in the treatises on brain disease. So far as I am aware no practical use has been made of this knowledge outside the domain of medicine. Yet it would be very strange if, from the ways in which the use of language is lost, or suffers varying degrees and kinds of impairment, we could learn nothing as to how it may best be acquired. The loss occasioned by the destruction of any language center is an indication of the defect that must result from neglecting to cultivate the same center by practice; and, as disease selects now one and now another center for attack, we
Diagram of the Left Side of the Brain. (Modified from Ecker.) A, auditory center; M, motor speech center; V, visual center; G, writing center; Sm and T. probable centers for smell and taste (dotted because on inner surface); S, provisional location of areas for perception of touch, pain, and temperature; Mu, provisional area for muscular sense.
learn the extent to which each is necessary in hearing, speaking, reading, or writing.
In the accompanying diagram of the left side of the brain, the areas marked A, M, V, and G are the four language centers. The dotted lines indicate the paths of fibers which connect them with one another and with other centers, carrying nervous impulses somewhat as a wire carries an electric current. The corresponding centers on the right side of the brain are for the most part rudimentary, and may for the present purpose be neglected.
The auditory center, A, receives the nervous impulses started by sound. When it is aroused by impulses coming from the ears, the sensation of sound occurs; but when it is aroused by nerve-currents, not from the ears, but from other parts of the brain, we have only the memory of sound. For a word to be understood, the auditory center alone is not sufficient. The sound must awaken the memories of other sensations. The word "orange," for instance, has a meaning because the auditory center, when the word is heard, arouses in the visual center the memory of the color and form of an orange; in the centers for touch, temperature, posture, and muscular sense, the memory of the sensations which occur when the fruit is grasped by the hand; in the centers for smell and taste, the memory of its peculiar odor, flavor, and tartness. These sensations are said to be associated with the sound of the word, and together with it they constitute the concept "orange." The nerve-currents passing from one center to another are called association impulses. If we have often eaten oranges, and at the same time heard the name, the auditory center whenever it perceives or remembers the sound will send vigorous impulses to the other centers, and the idea will be vivid. But if our experience of oranges has been very limited, or if the name has been rarely heard, or if instead of the correct name a merely similar sound has been heard, the association impulses will be sent slowly, feebly, and uncertainly, so that the idea will be vague. Prompt and strong associations should be cultivated as a means of securing clear and vivid ideas. The auditory center is the first language center to be developed. A child hears soon after birth, and toward the end of its first year the sounds of a few words are understood. Up to this time no words have been uttered, but the child now begins to imitate the sounds it understands and soon can use them. This requires the co-operation of the motor speech center, M, which by connecting fibers and the currents they carry combines the simpler movements of the vocal organs to form words. In the case of Gambetta, who was a loquacious politician and very successful orator, this center was excessively developed, though the brain as a whole was not remarkable. On the contrary, a study of the brain of the distinguished statistician, Bertillon, who was diffident and reticent, showed a high degree of general development, with an almost rudimentary motor speech center.
In speaking, the guidance of the auditory center is necessary. The sound of a word must be remembered when it is uttered. On the other hand, the effort of the motor speech center to utter a word reacts upon the memory of the sound, causing it to be more vivid. In the main the two centers work and develop together, but the auditory center is the more independent and fundamental. If a child becomes deaf, even as late as the tenth or eleventh year, it also becomes mute, unless special educational measures are employed; and in adults destruction of the auditory center interferes sadly with talking, while destruction of the motor speech center does not seem to interfere at all with the understanding of speech.
When reading is first undertaken, the auditory and motor speech centers with their association fibers are already well developed. The visual center, V, now begins to work with them. When impulses from the eyes reach this center, the sensation of sight occurs. The appearance of each letter calls up the memory of its sound through the association fibers, V A, and a number of these elementary sounds uttered in quick succession are recognized by the learner as a word. Its meaning is awakened by the auditory center, and at first it is necessary to read aloud in order to make the association impulses from this center sufficiently exact and vigorous. Later, the memories of the sound and of its utterance suffice without its actual reproduction, but in most persons these memories remain an essential part of the reading process throughout life. As this is read, the reader is doubtless conscious of the sound and of the incipient utterance of each word.
In learning to write, the motions of the hand become automatically associated with the memory of the corresponding utterance. It might be supposed that in writing the appearance of each word is recalled and copied; but this is not the case, although the visual memory may be an aid to correct spelling. Words may be written with no recollection of their appearance.
The correctness of the foregoing statements is proved by the effects of disease of the language centers, as shown by observation of speech defects during life, followed by post-mortem examination of the brain.
Destruction of the visual centers of both sides causes blindness; but when these centers themselves are unharmed, disease may be so situated as to cut off their communication with other centers. In this case the patient sees, but does not recognize what he sees, and is said to be mind-blind. If the affection is so slight that he can still recognize ordinary objects, but not written or printed words, which are more difficult, he is only word-blind. To a person afflicted with word-blindness the print of his own language is like that of a foreign one. George Eliot, with her usual sure touch in medical matters, gives an interesting illustration of this affection in the case of Tito's foster-father, Baldasarre; yet Romola was finished in 1863, when very few physicians were aware of the existence of such cases. Reading in such a case is, of course, impossible; but writing is not prevented, although the patient can not read what he has just written. Speaking and the understanding of speech are not interfered with at all.
Destruction of the motor speech center causes a much more extensive interference with the use of language. The motions of the vocal organs being no longer co-ordinated, an inarticulate jargon, or the senseless repetition of a word or phrase, is all that is left of the power to talk. The ability to write is also lost. Reading aloud is, of course, impossible; but it is also a matter of common observation in such cases that the ability to understand print is lost or greatly impaired. This proves that in most persons direct associations between visual words and ideas, if they exist at all, are too weak to be depended upon. So the understanding of spoken words is the only way of using language that is independent of the motor speech center.
But it is destruction of the auditory center that causes the most extensive loss of language. In such a case words (though they may be heard through the right side of the brain) are not understood. This failure to understand is called word-deafness. But there are other serious defects. Although the vocal apparatus is in perfect order, and there are ideas seeking expression, the words uttered are mutilated, deformed, and often totally different from the ones intended, so that intelligible speech is wellnigh impossible. This shows that in talking the most important association impulses do not go directly from the centers for ideas to the motor speech center, but to the auditory center, which, remembering the sounds, by fresh impulses arouses the motor center to utter them. Writing is still more interfered with, because it depends upon the utterance-memory, which goes astray without the sound-memory.
Does destruction of the auditory center also prevent reading? We should expect it to do so, from the way in which reading is learned, and excellent authorities say that it does. There is not enough simple and direct evidence (consisting of the inability to read during life, followed by the discovery of disease limited to the auditory center after death) to prove this, on account of the small number of available cases and the lack of attention to reading in the observation of many of them. Making allowance, however, for the difficulties in the way of gathering direct evidence on this point, the cases published support the view that in most persons the auditory center is essential to the understanding of what is read. But there is other evidence that is quite convincing. We have seen that in reading the visual center can not, as a rule, call up the ideas, else destruction of the motor speech center could not interfere with reading as it does. Nor is the motor speech center directly connected with the centers for ideas; if it were, destruction of the auditory center could not interfere with talking as it does. This leaves only the auditory center, which is abundantly capable, for the sounds of words readily awaken ideas before the other language centers begin to work and after they have been destroyed. Therefore, the auditory center must do the essential work of rousing ideas in reading. But if it does this, why is the motor center needed at all? We have seen that a beginner has to read aloud to stimulate the auditory center to do its work. In quiet reading the utterance-memory probably reacts upon the sound-memory, making it more vivid, and thus causing the auditory center to send out stronger association impulses. Possibly visual words first arouse a memory of the utterance instead of that of the sound, as I suppose. But, be this as it may, the facts clearly indicate that, in the evolution of language, the auditory center has acquired the position of a central station, through which the other language centers communicate with the centers for ideas. The sound of a word is the word itself. Printed words are only convenient symbols for recalling the sounds.
This gains in interest when considered in the light of Max Muller's views concerning the relation of language to thought. His motto is: " No reason without language; no language without reason." He contends that the scattered sense-memories can not be bound together to form a concept without a word, so words are essential to thought. He does not mean thought to include the inference that a dog makes when he sees his master start for a walk, or that which a driver makes when he sees a stone ahead of him and pulls the rein to avoid it. Undoubtedly such mental processes may go on without words. But it must be acknowledged that general or abstract thinking, such as places man so far above the lower animals, does require the use of words.
Now, what are the words that are essential to such thinking? Surely not visual words, but the words heard and uttered, as any one may know by attending for a few moments to his own thinking. And do not all the philologists tell us that the laws revealed by a study of the life and growth of language are phonetic laws?
Max M filler also alludes to the interesting distinction made by the German language in the two forms for the plural of Wort. Worte means living words actually engaged in conveying concepts from one mind to another; Woerter means words considered as mere objects. Visual words are only Woerter, dead bodies unable to support the burden of thought, mere effigies of the living sounds.
It is not meant, however, to deny the possibility of a different relation of the language centers to one another in abnormal or in exceptional individuals. Deaf-mutes may learn to read and even to speak, and doubtless to use visual words in thinking; but it is with much more than ordinary difficulty, and, in the opinion of some of their ablest teachers, the results are not so satisfactory as to warrant the abandonment of the more primitive signlanguage. And it is a fact of great significance that those deaf-mutes who have once been able to hear, though the subsequent deafness was total, have a great advantage over those deaf from birth, not only in learning to read and speak, but in general mental capacity.
We are now ready to apply our facts to the practical question of how best to learn another language than our own. One method, still prevalent in schools and colleges, attempts to extract the language almost by sheer force of memory from grammar and dictionary. It has never been claimed that by this method the ability to converse could be acquired, but it has been generally assumed that by it the pupil could at least learn to read, and perhaps, if diligent, to write to advantage. Yet, even for this purpose alone, the grammatical method must be a failure in so far as it neglects to train the pupil to a quick perception and a ready utterance of the sounds of the language, for we have seen that the auditory and motor speech centers do an essential part of the work in reading and in writing. Even if direct associations from the visual center may be cultivated, as in the case of deaf-mutes, why, instead of an easy and natural method, choose an unnatural and difficult one that leads to poor results? If it should be claimed that the grammatical method, without special attention to pronunciation, does enable pupils to read, and read well, in spite of any theorizing on the subject, then it must be said without hesitation that the claim is not warranted by facts. The remarkable unanimity with which the vast majority of our college graduates neglect to read the ancient authors is a very significant thing. It seems that they are not really able to read the Greek and Latin writers, but only to make a translation, and that they find no sufficient reward for this slow and irksome process.
As applied to the modern languages, the grammatical method is, even at its worst, supplemented by considerable exercise in pronunciation, and the ability to read with pleasure and profit is attained in a correspondingly higher degree. Yet, in estimating this ability, there is much room for self-deception. The pupil, after memorizing inflections and rules of arrangement, begins, with the constant use of the dictionary, to read, or rather, at first, to make a translation. Persevering, he finds that he needs the dictionary less and less, and perhaps he begins to understand without the use of English equivalents. Now, let us suppose that he has reached that point where he is able to read page after page without any absolute necessity of referring to the dictionary, or even of calling up an English word. Has he, as he is apt fondly to imagine, mastered the language as far as reading it is concerned? Not at all. He has made a respectable and useful acquisition, but it is far from being perfect. Let him read a chapter of French or German, learned in this way, and then read the same amount of English—on the same subject, and, as nearly as may be, in the same style and he will find a great difference in the time required. Let him read a plain narrative in the foreign tongue, and he will find that weariness importunes him to stop much sooner than it would if he were reading a good English translation.
Nor is this all. The meaning has been more or less misty throughout, as can readily be proved by taking the individual words out of connection and finding that many fail to call up any definite idea. Arid, although the ideas have appeared during the reading, they have been faint instead of vivid, because the association impulses have been sluggish and uncertain instead of prompt and true. Moreover, the subtile correspondences between sense and sound, which are allied to the unexplained power of music, together with almost all that constitutes the charm and effectiveness of style, have been lost in a struggle to get the bare meaning no, not even the bare meaning, but a bare skeleton of the meaning. If this is a serious loss in reading plain narrative or scientific exposition, how fatal is it to the full enjoyment of poetical or rhetorical writings, where every word has been chosen with some reference to its sound! The readers of Hamerton's wise and charming essays on The Intellectual Life will remember how Tennyson's Claribel was read by a thoroughly cultivated Frenchman, who had long studied English and read abundantly of the literature, but had never become really familiar with English sounds:
"At ev ze bittle bommess
Azvart ze zeeket Ion
At none ze veeld be ommess
Aboot ze most edston
At meedneeg ze mon commess
An lokez doon alon
Ere songg ze lintveet svelless
Ze clirvoiced mavi dvelless
Ze fledgling srost lispess
Ze slombroos vav ootvelless
Ze babblang ronnel creespess
Ze ollov grot replee-ess
Vere Claribel lovlee-ess."
Ought we to be content to read the French and German or the Greek and Latin poets in any such fashion?
But even such absurdly incorrect sounds serve some purpose, for they keep the association currents in their natural course through the auditory center. They are like a debased and mutilated currency, whose low and uncertain value discourages and confuses trade, but which may, in default of anything better, still keep the stream of commodities flowing in the natural channels.
Now suppose a student, having reached the stage of progress above indicated, visits the country whose language he has been reading. What he hears at first is almost wholly unintelligible, though the same words in print would be familiar. A little later it is not uncommon to hear a sentence without comprehending it at all, when suddenly it will flash upon the mind of the hearer as though seen in print and pronounced by himself, and then it is readily understood. The same thing occurs in listening to one's native tongue when the auditory center has been slightly damaged by disease.
In these cases the damaged or un practiced auditory center recognizes but a part of what is heard, but this is enough to suggest to the well-practiced visual center the complete memory of the visual words, which then calls up their usual, possibly incorrect, sound and utterance, with the associated meaning.
As time passes, the strange sounds, through constant repetition and efforts to imitate them, grow familiar and become strongly associated with every-day experiences, so that as soon as a word is heard the idea is vividly present in consciousness. If the student reads now, he finds his former disadvantages greatly diminished. He reads faster and with less fatigue, finding a clearness and vigor of meaning before unknown. It is not because his vocabulary is larger, but because it is more efficient. The auditory center, which formerly, through lack of practice, failed to properly perform an essential part of the work, is now, at the suggestion of the visual center, quick to recall each sound, and, re-enforced by the utterance-memory, it is quick, accurate, and vigorous in reviving each idea. The work of exchange is now done by the true coin of the realm.
The more carefully any teacher or thoughtful student will consider his own experience, the more he will be convinced of what the facts of brain disease demonstrate, that a good method of learning any language, whether the aim be to speak or only to read, must make the thorough training of the auditory and motor speech-centers a fundamental object. This training can be perfectly attained only by living where the language to be learned is spoken; but, although the difficulties at home are great, if the essential requisite is only kept in view, a great deal can be accomplished. This we owe to the clear insight and faithful work of the inventors of the natural method. Although this method is well known, it may not be amiss to give a sketch of how the best results may be obtained.
The first part of the course of instruction should be devoted exclusively to the sounds of the commonest words, their reproduction by the pupil, and the formation of strong associations between them and actual experiences.
The correct sounds must receive a degree of attention and reverence that would do credit to a music-master. Inevitable awkwardness in pronunciation should be corrected, not only by repeated efforts to imitate what is heard, but also by careful instruction as to the exact position and movements of the vocal organs in making the difficult sounds. This is of great importance, as it reacts upon the auditory memory and does much toward fixing a clear conception of the correct sound of each word. Probably very few Germans or Frenchmen have a clear conception of the sound of "th" in English; but had they from the first, whenever attempting this sound, been required to place the tip of the tongue between the teeth (which is never done in speaking French or German), there could be but little difficulty in pronouncing or recalling it. And in the same way a clear understanding of the fact that the French u and German Umlauts require the lips to be thrust forward and partially closed, will enable one to acquire these sounds far more readily than he otherwise could.
An objective expression of the meaning of words and sentences should always be sought. Things actually impressing the senses cause a more vigorous action of the brain than any recollection of them; consequently they make associations stronger and meanings more vivid. Although the exhibition of common objects and pictures, in teaching a vocabulary, may to the superficial observer seem childish and wasteful of time, it is in reality wise and economical.
The memorizing of sentences, reading aloud, listening to others read, and writing from dictation should all be employed, in addition to simple conversations between teacher and pupil, as valuable exercises. What is read at first should be carefully graded, so that the ideas may be awakened without having recourse to English, thus avoiding the habit of making a bad translation, which is often injurious to a school-boy's use of his own language.
As a pupil in the first stage of progress is pretty sure to go astray when left to himself, the work should be so arranged that all the time allotted to the language may be spent with the teacher. Tasks for outside preparation should not be assigned until the appreciation of the correct sounds is keen enough to prevent the contraction of vicious habits of pronunciation. Grammar should at first be taught only as it becomes available for immediate use; but, later in the course, it should be taught systematically, and copious outside reading should be assigned.
A student who can neither go abroad nor command the services of a good teacher is at a great disadvantage; but he may still, if he has had a fair start, do much toward the cultivation of the auditory and motor memories of the foreign words with their proper associations, and thus greatly improve his ability to read. He should attend carefully to pronunciation, and practice reading aloud. When a new word occurs, the first thing is to get its correct sound, and the next to associate it with some actual experience, if possible; if not, then with as vivid an idea as can be recalled. The English equivalent must be dropped from consciousness as soon as the idea is present, so that the association may be a direct one. It is an advantage to use a dictionary with words and definitions in the same language. Reading on subjects in which one is specially interested is much better than general reading. The memorizing and frequent repetition of interesting passages will pay abundantly for the time and trouble.
The great difficulty in working alone is to hear enough of the language to keep the auditory center familiar with its correct sounds. To this end, every opportunity should be taken to converse, or to hear a sermon or a play, in the foreign tongue. In many American cities such opportunities are not rare, especially as to German.
For this purpose the phonograph will no doubt be made of great service. With its aid choice passages in literature or scientific exposition, as rendered by a good reader, can be repeatedly heard and pronunciation and accent imitated at the pupil's convenience. I have no doubt that some process of cheaply multiplying the phonographic cylinders or ribbons will, before very long, enable us to enjoy whole books in this way, thus saving our weary eyes and economizing the energy of the brain, while giving a greater pleasure.
I see no reason why Latin and Greek may not be taught to advantage by some such method as the one that has been outlined. The uncertainty as to what the original sounds were, though embarrassing, is not nearly so great as one would naturally suppose. Philological science has reached such perfection that at least a close approximation to the correct sounds could be agreed upon and registered by the phonograph.
As Hamerton suggests, a phrase-book could doubtless be made for teaching each language by the natural method. A student once fairly started in this way could not fail to make greater progress in grammatical and philological knowledge, as well as to find the classical authors more interesting.
In conclusion, it may safely be said that the reader who has given his assent to the deductions here made from the facts of disease will not hesitate to go further and concur in the opinion that pedagogy will in the future find a scientific basis in a knowledge of the functions of the brain. Its career must somewhat resemble that of the art of medicine. There were great physicians before Harvey found a starting-point for scientific physiology; yet the debt of practical medicine to physiology is now well-nigh incalculable. So it will be with the art of teaching: noble work has been done for its advancement in entire ignorance of the organ whose best development it seeks; but now, since there is already a large and constantly increasing fund of knowledge concerning the working of the brain, teachers who are not bound to the traditions of the past, but are looking eagerly for every means of improving their art, will assuredly not fail to take advantage of the new knowledge.
The result must be an enormous gain for the children of the future.
An influence of a total solar eclipse on air pressure has been deduced by Herr Steen from the comparison of the records of fourteen Norwegian ships between Panama and Madagascar, during the eclipse of August 29, 1885, four of the ships having been within the zone of totality and four others very near it. Two maxima of pressure, separated by a minimum, were revealed. The double wave is explained by Herr Steen by assuming that during a solar eclipse day is changed to night for a short time, and the transition is much like the ordinary change from day to night in the tropics, where the twilight is short. There the curve of air pressure has regularly a maximum about 10 p. m., some time after sunset, and a minimum about 4 a. m., shortly before sunrise; while a second maximum appears about 4 a. m. A total solar eclipse would naturally act in a similar way.
- References.—Any reader interested in the foregoing argument would do well to verify the statements of fact on which it is based by reference to some of the following well-known authorities:
For a very clear, popular account of the functions of the brain, see Prof. M. A. Starr's article, The Old and the New Phrenology, Popular Science Monthly, October, 1889.
For a more complete account, consult the same author's Familiar Forms of Xervous Disease; Gowers's Diseases of the Nervous System, pp. 454-465, American edition; and the text-books of physiology by Michael Foster and by Landois and Stirling.
For defects in the use of language, besides the above, see Th. Ribot, Diseases of Memory, chap, iii; Moebius, Allgemeine Diagnostik der Nervenkrankheiten; Ross, Diseases of the Nervous System, chap, xviii; H. C. Wood, Nervous Diseases and their Diagnosis, chap, ix; Gowers, loc. cit., pp. 540-555; also Starr, The Pathology of Sensory Aphasia, Brain, July, 1889, and Apraxia and Aphasia, Medical Record, October 27, 1888.
For a discussion of word-blindness and mind-blindness, illustrated by cases of great interest, see Charcot, Lecnns sur les Maladies du Système Nerveux, tome iii, pp. 154189.
For a discussion of the working of the brain in reading, with references to previous researches, see Ein Beitrag zur Lehre von den Lesestoerungen, Weissenberg, Archiv f. Psychiatrie, xxii, 2.
The most philosophical and elaborate work on the disturbances of speech is that contributed by Kussmaul to Ziemmsen's Cyclopædia, vol. xiv.
In consulting any author on this subject the date of writing must, of course, be considered, as every year adds materially to the common store of available facts.