University of Edinburgh

Tactile Graphics

CHAPTER ONE: Illustrations in visual and tactile form

1.1 The need for graphic skills

Pictures and diagrams are a means of communication which fully sighted people take for granted, and on which modern society relies. If people who arc blind are to take full advantage of available educational, leisure and employment opportunities It is important to find adequate substitutes for all kinds of graphic displays.

The means are available to create various forms of tactile representations which can be understood by blind people, and even by those whose impairment was congenital. This book assesses the extent to which tactile displays can be substitutes for pictures, describes the way in which they should be used, and illustrates ways in which people who are severely visually impaired can be better equipped to obtain reliable information from them. In doing so, it examines the perceptual channels through which such tactile displays are read and interpreted, describes the associated experiences which are pre-requisite to full understanding and the type of educational programme which can enable blind children to acquire facility and confidence in the use of pictures and diagrams in their tactile form.

1.2 Pictures

If the word 'picture' is used in its most wide-ranging sense to denote any display in which information is given spatially rather than verbally it will encompass a vast range of graphs, symbols, maps and images on the one hand and will serve a wide variety of communicative intentions on the other.

Thus the conventional symbol for the toilet facilities fordisabled people advertises their presence with a stylised side view of a wheelchair and its occupant which is intended to be easily recognisable by people in the countries where it is used. Although this is generally so, there is no doubt that the reader would need to have met sufficient numbers of these wheelchairs and symbols of this nature to he able to guess what the symbol means. Some other symbols of this type are much more ambiguous. For example, the symbol based on the front view of the human eye with a diagonal line across it which announces the availability of help for visually impaired people is obviously linked to the eye in some way, but precisely what it means is much more difficult to guess. So symbols of this type do require users to be educated in a particular code, if not symbol-by-symbol at least to the extent of adopting a particular frame of mind in approaching the symbols.

The medical temperature or blood pressure chart indicates higher and lower temperature or blood pressure by raising and lowering the graph line, and traces the progress of these phenomena by a zig-zag. By convention the vertical or 'y' axis usually represents the measured effect of whatever controlled variable is plotted on the 'x' axis running across the chart. Mathematical information of this sort can be very precisely plotted so as to allow accurate reading from the graph by noting the coordinates at anyparticular point on the trace.

A statistical pie chart registers shares of a total by larger or smaller slices from the pie. The statistical symbolism of this type of presentation is very obvious but precise measurements are difficult to read back from the chart.

Process diagrams or flow-charts show the inter-relationships of stages in the process by lines of connection and direction. They are widely used for purposes as diverse as showing the chain of command in all organisation; demonstrating the steps in a biochemical process; or describing the manufacturing processes to he followed in producing an engineering product.

Simple maps indicate environment on a notional bird's eye view with conventional symbols. Maps can be made to various degrees of sophistication and in the case of the more complex ones such as the smaller scale, Ordnance Survey maps such features as contours may require considerable training to read whereas coastal outlines, roads and rivers nay be relatively simple to understand. There are also many occasions when instrument readings such as weather or seismic data are plotted on maps as a visual or spatial way of representing variations in the physical data. To read them intelligently requires full understanding of the underlying phenomena, of the way they are recorded, and of the implications of the data. To be able to read this kind of map one must acquire knowledge which goes far beyond the ability to discriminate and identify the shapes and symbols on the page.

These are just a small selection of the ways in which information is conveyed diagrammatically. Yet none of these examples begins to consider that world of pictures which is generally thought of as 'Art', and covers a vast spectrum of the 'old master' in oils, through pastel sketch, etching, water colour to cartoon and every school from the consciously representational to abstract and pop-art. With these pictures, style and historical or cultural development Influence the way the picture is perceived. (Gombrich, 1960, pp 264 -275) These factors influence not only the way the artist responds to what he sees and tries to depict, but also the way in which the viewer reacts to and understands the picture. (Artist and viewer may, of course, he separated by centuries of time.)

With the scope and intentions of pictures being so varied, what then is the potential of two-dimensional and three-dimensional representations when they can only be read by touch in the way that a blind person would?

It must be established from the outset that even in that subset of visually impaired people who have no vision at an there are two quite distinct groups of people: those who are Late Blind who may have distinct visual memories which may be depended upon in concept forming, and those who are Congenitally Blind and have no such memory. There has been a tendency in the past to postulate limits to the understanding of congenitally blind people that now appear to be quite unwarranted in the light of experience and more careful research. (Birns, 1986). Undoubtedly those who are congenitally blind begin their lives with the disadvantage of a much reduced and biased sensory experience and if this is not overcome by adequate educational measures a severe educational and cognitive handicap can occur.

However, many of the most damaging aspects of this can be minimised by providing rich enough tactual and conversational opportunities during and beyond childhood, and among such measures tactile pictures have their part. Well educated congenitally blind children cannot overcome their disadvantage entirely - one would be foolish to pretend otherwise - but their effective educational performance can come very close to that of the late blind in most respects and can enable them to lead full and interesting lives open to new perceptual opportunities. These educational questions will be re-examined in more detail later in this book.

1.3 Representations for the touch sense

That touch is the Cinderella among the senses becomes apparent from a cursory glance at the contents page of any handbook of perceptual psychology. The small proportion of such a book devoted to touch echoes the relative proportion found in academic publications as a whole, and it also reflects the general pattern of research activity and public interest. It is significant that David Katz 'World of Colour' which deals with visual phenomena has long been available in English translation, whereas his influential 'Aufbau der tastwelt' on the subject of touch call still only be read in Its entirety in the original German. (Katz, 1925 and 1935)

There is a corresponding deficiency in the development of tactile educational resources, despite a conviction by developmental psychologists that tactual input is a potent factor in every child's early development and in the establishment of effective psychomotor pathways in skill learning. Indeed visual information only takes on its full significance for the young fully sighted child when he/she is able to relate it to the tactual world. (Bower, 1974) Some of this deficiency of resources is caused by the relatively low number of children who would appear to benefit, so that potential producers are not encouraged by any prospect of commercial advantage.

In the more specialised area of tactile illustrations for those who are severely visually impaired, examples of the genre are nowhere near as numerous as the great variety of visual illustrations even though experience of using tactile media in education and knowledge of presently available technology leads the present author to believe that we exploit only a trivial fraction of the potential of this means of communication. Despite progress in the understanding of tactual perception made by researchers over a range of disciplines, our understanding is still patchy and seemingly more prone to make wayward turns than in other branches of psychology.

Yet much of knowledge deals with structures and processes whose stages and inter-relationships are most clearly described by some two or three dimensional pattern, Words alone, If they are to provide an adequate description, may be cumbersome by comparison with a sketch, however crude it may be, this book attempts to extend the available knowledge of the use and understanding of tactile representation in formal and personal education by drawing together some of the experimental results of researchers, teachers and users, including results or the author's own research, and by describing and discussing the relevant design and pedagogic issues.

The literature referring to tactile graphics is complicated by the fact that much research on tactile illustrations is based on the use of illustrations of poor quality and outdated style, and the pessimistic question of Merry and Merry (1933) as to whether tactile pictures have any use at all is an extreme but not isolated instance of this. Views of this kind are even now occasionally repeated uncritically.

From the practical point of view it is also important to consider tactile features in context, because the context in which they appear has a marked influence on their effectiveness, or indeed on the meaning that people attach to them. (Hinton, 1988a, p13) Controlled experimentation has often considered picture components in isolation, (Nolan and Morris, 1971; Lederman and Kinch, 1979) yet when set within an illustration their effect may be different. (Hinton, 1989a)

The teaching environment in which they are used is also a vital factor for effectiveness. The writer's own earlier trials of tactile diagrams confirmed that the performance of this type of teaching resource was much better where the pupils were put at ease and were given adequate support than where they were left to flounder on their own. (Hinton, 1988a, p.15) This book will attempt to link together and evaluate all of these factors in the use of tactile media.

1.4 What is the nature of a tactile diagram?

As tactile diagrams and pictures will be referred to frequently throughout this book it is necessary to give a straightforward description of their nature.

Historically the tactile maps and diagrams that were first produced were collages of textured materials which were intended to be felt directly. Obviously, as soon as education of the visually impaired took place on a scale bigger than one-to-one it became a very laborious task to create enough copies of each diagram for each student to have one, although this is plainly essential for a comfortable working environment. When the thermoform machine for polymer sheet became available for the reproduction of Braille text it was realised that this process also offered a means of reproducing copies from a master diagram, and this method became adopted as a standard technique in the 1960s, with the quality of master diagrams at that time rarely matching the potential of the means of reproduction. Not surprisingly there was much doubt among teachers about the usefulness of  tactiles to blind children, despite the efforts of pioneers like Pickles (1968) to improve standards and clear evidence from pupils themselves that tactiles could be useful when properly designed and presented.

In the thermoform (sometimes called vacuum formed) method of reproduction the master diagram is placed on the work-platen of the machine with a thin sheet of a polymer such as PVC damped over it. The work platen is then slid under an electric heating element which warms the polymer to soften it. After a suitable delay, set by the switch panel of the machine, a vacuum pump is switched on automatically, and this draws out air from beneath the polymer sheet to draw it tightly down onto the master diagram so as to follow its contours exactly. The work-platen is then withdrawn from the heating element, and after· cooling the copy is gently stripped off the master mould. By repeating the process, many copies can be produced from a single master mould. Although there may be slight changes in texture and some loss of definition in comparison with the original mould, an experienced designer can allow for this in making the original. This method of production is still highly relevant to today's educational needs, despite further technological advances, because the greater variation in form, relief and texture which it offers will permit good discrimination of complex subject matter.

1.5 Microcapsule (Zychem) diagrams

An alternative method which has come into vogue since 1980 is the use of microcapsule diagrams (currently produced by Zychem), although 'swell paper diagrams' is another term which some people use. The special coating of the paper used for these diagrams contains minute PVC microcapsules of an organic solvent. When a black-and-white diagram is photocopied onto this paper and then heat treated, the black lines of the diagram absorb more heat than the white areas and cause the microcapsules to expand so that the lines of the diagram swell up above the general level of the paper to create a tactile shape.

Unfortunately every line is raised to the same extent so that while this method of production is useful for many diagrams of an open texture, diagrams of a more complex structure tend to he much more difficult to decipher unless they are expertly designed. Despite this, the process is widely recommended, often for unsuitable tasks, and the reason for this is largely speed and ease of operation. The process can also produce images which are visually clean and appealing, however unsuitable they are for a blind user.

In the author's work this kind of diagram really comes into its own when the original diagrams are computer generated, and a production unit based around computer graphics facilities can be very responsive to a variety of educational needs.

1.6 Drawing on German film

A third method of producing a tactile picture involves a material known as 'German Film', although there are earlier materials with similar behaviour known simply as 'drawing film', Sewell film or Melinex. 'German Film' itself is a translucent and lightly textured polymer sheet which was originally developed as a backing-sheet for medical wound dressings. All of these materials lift lip to form what can best be described as "a touch-detectable scratch” when drawn upon with a simple scriber or ball-point pen on a soft rubber backing pad. Unlike the other two methods this is a way of producing a sketch rapidly during an actual lesson, and it can also be used after practice by blind pupils to make their own drawings. Its use for both purposes will be described alt various points in this book. Its use complements the other two processes which are for more formal teacher presented diagrams. The German film method lends itself well to the active, two-way learning encounter. Here again the line produced is less distinct and of uniform height above the page.

1.7 Scanning and learning

Much of the published intensive research on tactile diagrams (Nolan and Morris; Berla; Bentzen) has been directed at discrimination, scanning and tracking needs and has been carried out in the context of a controlled experiment involving a simple texture or symbol matching test, a tracking test (often on a carefully devised 'pseudomap') or some kind of scanning exercise.

Such controlled experiments are a necessary step in the process of learning about tactual displays in general, and particularly about map-like formats. The important information which is gained by this kind of research does not, however, tell the whole truth, even about map use, and particularly where the more pictorial forms of display are in use, new contextual factors operate within the overall perception. A  whole new series of considerations has to be addressed when the tactile is being used convey real information in the classroom.

A similar situation is met by mobility specialists  who use a tactile map to provide way-finding information (Bentzen). For example, a given texture or symbol must be not only discriminable, but meaningful in the context in which it is used.

In picture format it is also clear from the author's observations between 1985-1992 that with experience and confidence a blind person may recognise features of a picture (or an object) quite rapidly, and without first going through a process of exhaustive exploration and introspection. Teachers and lecturers working with blind students occasionally say, 'Well of course, tactile pictures are read just like braille. The fingers scan across the page serially from left to right, and then finally interpret what is felt.' None of the writer's observations suggest that this is generally so, although it is possible to think of a few diagrams whose structure would cause the reader to work in such a manner. What generally seems to happen is that structures and components quickly emerge from the picture as a gestalt during the preliminary touch of the page, and that meaning is then attached to these by the reader. Recognition can be in some cases quite rapid - so rapid that it appears to be instantaneous.

As this book will stress repeatedly, this recognition only comes as a consequence of more fundamental handling experience, operating un two levels:

a) the level of simple shape in the geometrical sense; and
(b) the level of form and organisation as found in the subject matter under study.

For example: a picture of an apple is identified first as a slightly deformed circle or sphere and then it is recognised within a subject context as fruit and apple. As the percept takes shape at each level the reader may need to check the presence or absence of additional minor features to select the most likely contenders from and range of possibilities before eventually arriving at a diagnosis.

1.8 Method of reading tactiles

There are fairly definite strategies for the reading of braille text, which are universally taught in order that the reader keeps his/her place and doesn't overlook anything. This may include the co-ordination of two hands, or the use of one hand as a place marker while the other reads. It is more easy to miss things by touch than when reading visually. Berla (1972) Investigated the use of similar reading strategies for tactile maps and did not reach such clear-cut conclusions. His only generally applicable conclusion was that some systematic strategy was beneficial in ensuring that important features were not overlooked, but of several possible approaches which he encountered, it was not very important which one was adopted as long as the reader was in some way systematic. Unsystematic readers tended to make errors and overlook things.

Berla's tactile maps, like most such examples, were in a clearly defined rectangular format. Not all tactile pictures are framed in this way. In fact the frame could often simply add to the clutter on the page. Unframed diagrams naturally need to be approached with even more flexibility, although the need to ensure that the preliminary handscan is all inclusive is still important.

As will be described elsewhere, when a more experienced blind user approaches on of the more pictorial representations, rapid conclusions can be drawn from an early partial exploration of the picture, and this may be sufficient to convey the necessary information. Part of the person's education needs to be directed towards strengthening the judgement which allows the reader to decide when enough information has been obtained or when, conversely, a display needs to be explored more thoroughly. A blind reader needs to learn to take risks, backed up by considered judgement, in order not to be permanently handicapped by slowness.

All of the types of diagram discussed in the first few pages of this book have their tactile counterparts. The ease with which they can be read will depend upon whether they are closely related to things that can be felt with the hands or whether they have some obvious variant which can be learned and associated with mathematical or other information. Every new situation may require its own special kind of information but the reader must be taught to approach all diagrams and pictures in a manner which is likely to extract any necessary information from the tactile page. The features of an adequate educational curriculum to make the best use of these diagrams will be discussed later in this book.

1.9 Pictures as a visual phenomenon

This book will sometimes consider pictures as a visual phenomenon besides dealing specifically with tactile pictures and tactual perception, because the overwhelming majority of the writing on picture perception deals with the pictures of the visual world. It would be unwise In make too great a digression in this direction, but there is copious information on the perception of pictures and natural scenes from those concerned with perception in animals (Sutherland, 1963); from those concerned with cognitive research (including more recently those whose interest is related to object recognition by computers and in aspects of artificial intelligence) (Watt 1988) and finally from those interested in picture perception from an artistic and historical standpoint. (Gombrich, 1960).

Because these insights contribute to our understanding of how a visual image is understood they have potential relevance to our response to other (eg tactual) sorts of image and some of them will be discussed further in Chapter Seven of this book.

Ron Hinton
First published 1996
ISBN: 0901580775