Senses in Double Harness
By JOHN NEWEY
AYOUNG man starting a scientific career in a professional or technical subject has to acquaint himself with an increasing range of topical knowledge as it appears in his special journals, and at the same time he has to read over the development of his subject in the _past fifty or so years. Naturally, with each annual increase in knowledge, each year's new student has behind him in time and before him for study a further volume of fact and theory for his attention. It is true that advance on any scientific front brings simplification, as all but one of several hypotheses fall before an established fact. This apparent simplicity is always short-lived: as further facts are added, and new hypotheses are required for their correlation.
All would agree that in many scientific fields, and especially in medicine, the rate of progress is very great; no one man can hope to stay in the vanguard of all fields of enquiry, and the general reader is left breathless by events. Since there is, as yet, no substitute for study of the written word in work of this kind; the student has, year by year, to undertake a larger and larger amount of reading. , It is reasonable, therefore, to give some thought to ways of overcoming problems of the vast field and increasing range of literature, and there are certain theoretical consider- ations which ,may be taken first. A method of solving the problem which commends itself to many is to exchange the tire- someness of holding up a book and turning the pages for the less severe disciplines of visual and auditory reception. With practice the student can achieve the art of watching and listen- mg, while thinking about other matters, until a fact which interests him brings back his immediate attention. Facility in this method is indispensable for all those accustomed to attending lectures, but it is not applicable to reading, because it is almost impossible to read while thinking about some other matter.
It is, of course, easy to carry out some routine, even compli- cated manual, task such as knitting, while reading, but the knitter must nearly always leave the book to count the stitches. It is common practice in most households to turn on the wire- less while reading; the auditory stimuli reach consciousness only when a point of interest is reached, and then the mind must be taken from the book. The question of televiewing does not arise because, since the same sense organs are used, it is impossible to watch the screen while reading.
Some will claim that they can scan a printed page, especially one containing short news articles, while engaged in conver- sation. On retrial it will be found that the mental effort of self-consciousness needed to plan* and then evaluate the attempt will so interfere with reception that it is impossible to be sure whether an auditory or a visual stimulus reached consciousness at any one instant of time. It is likely, though, that it is always the printed word which takes priority.
Certain stimuli reach the brain at all times but rarely reach consciousness : these are named proprioceptive, because they give information about the position of parts of the body in space, and this information is derived from sensory endings recording tension in muscles and ligaments. These stimuli can be summoned into consciousness at will, as when the position of a limb is described while the eyelids are closed. Consciousness of the position of the limbs is easy while atten- tion is devoted to the printed word. In the same way a fundamental stimulus like an itch can be recognised, localised and attended to without disturbance of reading. With few exceptions, whatever monitoring is being performed by other sense organs, it is the printed word which reaches consciousness when a book is being read.
It is easy, of course, to copy words from a book, that is to write while reading, and by speeding up the actions it is possible to read a word or two or even a line or two ahead of the writing. It is, however, very difficult to read an unknown passage from a book while writing down some other sentence; this can be done most easily when the written sentence has been carefully committed to memory or has been known for many years. Some schoolboys discover that the Lord's Prayer can, by constant repetition, be said out loud while the speaker's thoughts are elsewhere; in the same way it is fairly easy to speak .out a poem or a passage of prose which has been memorised, while reading or thinking. As some theatre- goers know to their discredit, it is possible to sing the National Anthem while glancing,at the programme, but it is very difficult to read an unknown passage while reciting or singing, and usually, on experiment, the recitation or song becomes staccato, so that, although the gaps are too short for analysis even by another observer, it is likely that perception of the written word has to be interrupted. for short periods and is not con- tinuous in the face of competition.
These abilities are naturally variable from person to person, and they can be increased by training, but it is not surprising that perception of writing is more delicate and more easily disturbed, being the latest of man's evolutionary achievements. Now, from a neurological point of view, the act of reading is a feat of bewildering complexity. Besides the controlled balance of neck- and hand-muscles, the co-ordinated gymnas- tics of the eye-muscles, the optical precision of the anterior and posterior chambers and lens, and the fascinating problems of transmission of nerve impulses by which the image is at last thrown. upon the cerebral cortex, there are to be reckoned with, in the reading of a single sentence, the brain's power of interpretation, analysis and memorisation. If there is one thing as certain as another about this mechanism, one of the medical student's nightmares, it is that there is much to learn, and that its capabilities are not yet fully explored. •
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