Popular Science Monthly/Volume 70/June 1907/Hygienic Requirements in the Printing of Books and Papers
| HYGIENIC REQUIREMENTS IN THE PRINTING OF BOOKS AND PAPERS |
By Professor EDMUND B. HUEY
WESTERN UNIVERSITY OF PENNSYLVANIA
THE cheapness and universal prevalence of printed matter, and the general enactment of compulsory education laws which fasten the reading habit upon all, give the problems of the hygiene of reading a universal and very great significance. This reading habit, when one thinks of it, has become perhaps the most striking and important artificial activity to which the human race has ever been molded. A very considerable part of most people's waking time, whether in childhood or in adult life, is taken up with the contemplation of printed or written symbols. One is seldom out of sight of some sort of printed or written matter, and the automatic functioning of the reading habit keeps one reading away at whatever appears, though it be but the silliest advertisement in a car or on a concert program.
And yet this reading habit is an intensely artificial performance, involving for both mind and eye and nervous mechanism, most delicate of all products of evolution as these are, constant repetitions of functionings which were not foreseen in their evolutionary development. I discuss elsewhere the nature of these unusual functionings and the causes of the fatigue and degeneration which have resulted from reading, and which must continue more or less until the organs become adapted to these requirements of modern civilization. The dangers from the strain on mind and eye and nerves, in reading, will be materially lessened if the schools, especially, will honestly enforce certain hygienic requirements that are now generally agreed upon, and statements of which are easily accessible in such recent books as Shaw's 'School Hygiene' or in the more comprehensive work of Burgerstein and Netolitzky.
Probably the most important and most feasible means of lessening the fatigue and strain of reading is by bringing about, so far as possible, that all books and papers shall be printed in such type and arrangement as shall fall within certain recognized limits of hygienic requirement. As to some of the requirements which should be made of the printer we are still uncertain, and further experimental investigation rather than the present excess of opinion is in order and is cryingly needed. Of some requirements we can now be certain, and these should be enforced rigorously, in the printing of school-books and government publications, at least. If enforced here, they will tend to extend to all printing.
In studying the psychology and pedagogy of reading during some years past, the writer has been thrown in contact with the experimental work bearing upon the establishment of norms for printing. The present article is an attempt to sum up the results of investigations made thus far, and to state the requirements which they warrant us in making of the printer.
The size of the type is perhaps the most important single factor. The experiments of Griffing and Franz showed that fatigue increases rapidly as the size of the type decreases, even for sizes above eleven point, or above a height of 1.5 millimeters for the short letters like v, s, etc. The various investigators are generally agreed that this should be made a minimum for the height of the short letters. Matter printed in this size of type is read faster, and individual words are recognized more quickly, than where the type is smaller. Besides, Griffing and Franz found that the effect of insufficient illumination is less marked with the larger type. Preferably the height of the small letter should be somewhat above the minimum stated, though when the height is much above two millimeters Weber's experiments indicated that the speed of reading is decreased.
The thickness of the vertical strokes of the letters should not be less than.25 millimeter, according to Cohn, preferably.3 millimeters, according to Sack. This thickness of the letters has been found by Javal and others to be a very important factor in increasing legibility and thus in decreasing fatigue. Griffing and Franz found, however, that hair lines might form parts of the letter without decreasing the legibility provided the other parts were thick. They find it possible, however, that such hair lines may increase fatigue. The minimum of thickness stated above should be insisted on for the main lines.
The space within the letters, between the vertical strokes, should not be less than.3 millimeter, according to most investigators. Sack finds.5 millimeter to be preferable. There is probably little to be gained by increasing the distance between the letters beyond that which is usual in the better printed books of the present time. Burgerstein and Netolitsky would require that this distance should be greater than the distance between two 'neighboring ground strokes' of a letter, and Sack would make the minimum distance.5 to.75 millimeter. Burgerstein and Netolitzky would not allow more than six or seven letters per running centimeter, and would require as much as two millimeters between words. With these requirements Sack is in agreement. It should be remembered that any very unusual separation of the letters of a word is distracting and should be avoided.
These minimal forms as stated by Burgerstein and Netolitzky should be made requirements, except that possibly the distance between letters is not so important as they urge. The minimum of six or seven letters per running centimeter is a convenient approximate gauge which can be quickly applied and is not too stringent.
Griffing and Franz found that legibility increased somewhat, though not greatly, with increase in the distance between the lines, with the leading, as it is called. Cohn thinks it important that there should be a minimum interlignage of 2.5 millimeters, and Sack requires the same. Javal does not find that interlignage increases legibility appreciably, and thinks that the space used for interlignage had far better be given to an increased size of letter without interlignage. The leading is doubtless a mistake when the size of type is below the requirements made above. The size of type should by all means be increased instead, as this is by far the most important of the factors conditioning fatigue. However, a certain amount of leading should be required in school books, at least, but hardly more than Cohn's minimum of 2.5 millimeters.
As to length of lines there is a general consensus in favor of the shorter as against the longer lines, with a tendency to favor 90 millimeters as a maximum, some placing the maximum at 100 millimeters. The latter is doubtless too high. Javal, who has studied the matter very carefully, insists that the maximum should be considerably below even 90 millimeters. He names as one of the principal causes of fatigue in reading, and as a cause tending to produce and aggravate myopia, the considerable amount of asymmetrical accommodation required as the eye moves along a long line, the amount increasing always with the length of the line. Even with the page squarely before the reader, unless he makes constant and fatiguing movements of the head while reading, the reading matter is always farther from one eye than from the other, except at a middle point, and the reader strains to accommodate for both distances, especially for objects held so near as is the page in reading.
Against the long lines is also to be urged the difficulty and distraction incident to finding the place at each turn to the next line, increasing always as the lines are longer. Besides, the longer lines require a greater extent of eye-movement for a given amount of reading. This comes from the fact, verified by various experimenters, that the eye does not traverse the whole line in reading, but begins within the line and usually makes its last pause still farther within, reading the first and last parts of the line in indirect vision. The amount of this indentation tends to be a constant amount irrespective of the line's length, and is consequently a larger proportion of the line's length in the shorter lines. There is thus an important lessening of eye-work in using the shorter lines. Indeed, I found that readers could read matter printed in lines of 25 millimeters in one downward sweep without any lateral movement of the eyes. With lines 30 millimeters long, the lateral movement was sometimes almost nil, and seemed to be due mainly to habit. In reading such lines in this way the eye's extent of movement is hardly more than one fourth or one fifth the amount needed for the same matter when printed in long lines.
When the shorter lines, generally, more words were read per fixation than with the longer ones. A magazine column having lines 60.5 millimeters long was in one case read at the rate of 3.63 words per fixation, while columns having lines 98 to 121 millimeters long required a fixation for every two words. Lines of a length approximating 60 millimeters are usual in newspapers and in my experiments were read with a minimum of eye-movement. The makers of the modern newspaper have felt the reaction of readers more, perhaps, than have the makers of books. Out of this experience has evolved the present practise of printing newspapers in narrow columns, the line-lengths of which are perhaps as near the optimum as can be determined at present, when we consider that much shorter lines give great inconvenience to the printer.
For books, also, the newspaper line-length is near an optimum so far as ease and speed of reading are the conditions to be considered. In the case of large books where the question becomes one of printing in one or in two columns per page the latter alternative should undoubtedly be chosen. For books of ordinary sizes a somewhat longer line may be used where this will contribute to convenience or beauty; but a book should not be used whose lines are more than 90 millimeters in length, and somewhat shorter lines are generally to be preferred.
One of the great advantages of the shorter lines is that they constantly permit the reader to see in indirect vision what his eye has just passed as well as what is just coming. Though the words of this related matter may not be clearly perceived, they furnish visual clues which keep the reading range further extended at each moment, a most desirable condition for all reading and especially for fast reading or for skimming. With such lines a hurried reader may glance straight down a page with only an occasional short stop, and may yet be sure that he has gathered the gist of everything.
Dr. Dearborn, in experiments made recently at Columbia University, found that the eye makes its longest pause near the beginning of the line, thus permitting a general preliminary survey of the line. A secondary pause of more than average duration is made near the end of the line, perhaps partially in review. He finds that lines of only moderate length facilitate these general surveys better than the longer lines, and finds also that they facilitate a rhythmical regularity of eye-movement, both being conditions which contribute to speed and ease of reading. His tests showed that such lines (a little longer than newspaper lines) were read at greater speed and with shorter pauses than lines of twice the length.
Dearborn argues, and correctly I think, in favor of uniformity in the length of lines, particularly in books for children. The reader drops quickly into a habit of making a regular number of movements and pauses per line, for a given passage, and broken lines confuse and prevent the formation of such habits. However, a slight indentation every other line may, he thinks, be of distinct advantage.
Dearborn thinks that a line of 75-85 millimeters combines a good many advantages, and we are certainly safe in putting 90 millimeters as a maximum, with a preference for lines of 60 to 80 millimeters.
The smaller books which can be easily held in the hand during the reading are to be preferred, and on the whole have grown in popular favor. The larger books usually have to lie on a support, which exposes the letters at an angle, greatly lessening their legibility and producing the equivalent of a material decrease in the size of type. As to the forms of particular letters, many changes are cryingly needed. However, further investigation is needed before we are warranted in requiring changes of the printer. We know that such letters as t, z, o, s, e, c, i, are comparatively illegible. C, e, and o are often confused with each other, and i with 1, h with k, etc. This confusion can be avoided by making certain changes in these letters, and their legibility can be increased. Certain excellent recommendations of changes in particular letters have been made by Javal, Cohn, Sanford, and others.
However, there are many things to be considered in making such changes, and further thorough and mature investigation is needed before any letter is permanently changed. The whole matter should be placed in the hands of a competent specialist or committee of specialists, to be worked over experimentally and advised upon in the light of the psychology of reading, the history of typography, esthetic considerations, the convenience of printing, and the lessons of experience generally. Changes should not be made on the single basis of experiments upon the comparative legibility of isolated letter-forms. A letter whose legibility in isolation is bad may sometimes contribute most to the legibility of the total word-form. Studies now being made of the comparative legibility of letters as seen in context will doubtless throw light on this point. The subject is too complex to permit the adoption of recommendations that are based on study, however careful, of any single aspect, or on anything that does not include a careful study of all the factors. It is high time, however, that there should be a rationalization of these printed letter-forms that have come down to us in such a happy-go-lucky fashion, and it is to be hoped that either the Carnegie Institution or some department of research in a well-equipped university may take hold of the matter and see that the work is thoroughly done.
Among further printing requirements that are important and that should be insisted on, the letters should have sharp clear-cut outlines, and should be deep black. The paper should be pure white, but without gloss, the latter being especially trying to the eyes. According to Cohn and Sack the paper should have a minimum thickness of.075 millimeter. Paper of a slightly yellowish tinge is probably not injurious and is preferred by Javal. But in general the legibility depends on the contrast between the black of the printed forms and the white of their back-ground, and colored or gray papers lessen this difference and thus diminish legibility. Pure white light gives the greatest legibility. The print of one side must not show through from the other, and the printing must be so done that it will not affect the evenness of surface of the other side.
It is important that wall charts and maps should not contain more names than are absolutely necessary for purposes of instruction, and that these should be in large clear type; or the most important names for reference at a distance and by classes may be in the large type, with the others in type fulfilling the requirements for school-books and for use by individuals at the ordinary reading distance from the chart or map. Burgerstein and Netolitzky advise that school maps should not present the physical and political features on the same map, in the interest of greater legibility. Names printed on colored map surfaces need to be in larger rather than in smaller type than that used in books, if legibility is to be maintained, as any other back-ground than white means diminished legibility.
The writing upon slates is considerably less legible than that upon good white paper. In the case of blackboards the surface is apt to be gray after erasing, and this, of course, lessens the legibility very considerably. It is important that the blackboard surface be deep black, without gloss from reflection so far as this is possible; and that it be kept clean, avoiding the gray effect. Teachers and pupils should acquire the habit of writing on the blackboard in a large plain hand, as the greater distance at which the writing is read and the usually diminished legibility makes this of importance, and especially in the primary school grades.
In stating the requirements above, I have had in mind the needs of adult readers and of the older school children. The younger children must have a type much larger than the minima there stated. The reading of young children has not been sufficiently studied to warrant a final statement of what should be required in the printing of their books. As the most usable approximate statement of what may properly be insisted on, and for the sake of uniformity, I quote here the requirements made by Shaw in his 'School Hygiene.' These requirements are none too stringent, except that sometimes some of the leading may well be sacrificed in favor of a type that is a little larger, for the third and forth grades especially.
"For the first year the size of the type should be at least 2.6 millimeters and the width of leading 4.5 mm."
"For the second and the third year, the letters should not be smaller than 2 mm. with a leading of 4 mm."
"For the fourth year the letters should be at least 1.8 mm. with leading 3.6 mm."
For some grades succeeding this the type should be kept well above the minimal requirements for adult readers.
Examinations of the school books in use in Germany, Russia, and other European countries, made at various times and places, have shown that usually from fifty to eighty-five per cent, of the books came short of hygienic requirements. American books are somewhat better, but include very many that are very bad. Even when the principal part of the book is in good type, there will often be large sections printed in a type so small as to be very injurious. The dictionaries and other books of reference have notoriously small print, and those with the smaller and poorer types should be mercilessly discriminated against. As Shaw rightly says, "Principals, teachers, and school superintendents should possess a millimeter measure and a magnifying glass and should subject every book presented for their examination to a test to determine whether the size of the letters and the width of the leading are of such dimensions as will not prove injurious to the eyes of children. If every book, no matter what its merits, were rejected if its type were too small, the makers of such books would very quickly bring out new editions with a proper size of type."