4.4 Haptic Low-tech Aids

deaf blind people have been able to perceive the speaker’s talking movements by putting fingers on the active parts of the speaker’s face (the TADOMA method). The user of this method holds the thumb lightly on the lips and the other fingers on the cheek and neck, thereby obtaining information about movements of the talking person’s lips and jaw, airflow and vibrations of the vocal cords, and so being able to perceive speech (Reed et al. 1992). This capacity of perceiving speech tactually is obtained only after considerable training, preferably from an early age (Schultz et al. 1984). For research on the mechanisms responsible for this tactile capacity an artificial mechanical face capable of producing information similar to that of a talking person was built by Reed et al. (1985) and investigations with this device analysed different components involved in understanding speech in this way (Chomsky 1986; Leotta et al. 1988; Rabinowitz et al. 1990).

Even if it is not the topic of this chapter, it may be mentioned that several tactile aids for the hearing impaired have been developed (Summers 1992).

4.3.3 Natural Capacity of Touch and Evaluation of Technical Aids

As discussed above, haptics has large potentials in many respects when working under natural conditions, including detecting edges, identifying objects and perceiving their texture, hardness, form and weight. It is important to remember these potentials when the efficiency of technical aids is investigated. Likewise, it is important to consider under what conditions the successful performance worked, especially what stimulus properties were available and what exploratory procedures were possible. When a device fails to provide the information wanted important reasons are probably that it is not successfully utilizing the capabilities of haptics, that is, that it does not provide the stimulus properties and exploration possibilities that are essential for the functioning of haptics. As will be discussed below, there are usually many constraints on these basic requirements for the working of present-day haptic displays in comparison with what is naturally available.

4.4 Haptic Low-tech Aids

High-tech is not a necessary requirement for useful technical aids for the visually impaired. This fact is demonstrated by the successful use of the long cane and the guide dog for mobility, Braille for reading and embossed pictures for pictorial information.

4.4.1 The Long Cane

A cane as an aid for the mobility of visually impaired people has been used for centuries. Its basic feature is that it allows the users to extend their arms to reach the ground and objects in front of them. Such an extension of the arm is typical for many tools. The contact between the user and the environment is at the tip of the tool, not at the hand holding the tool. This gives a kind of direct contact with

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the world simplifying perception. As humans use many tools, the introduction of the cane as a tool is considered to be quite natural.

Even if canes have been used for a long time, they were not used systematically until the twentieth century and especially after the Second World War (Bledsoe 1997). A key feature of the long cane developed at that time was that it was long compared with the canes used previously and that it should mainly be swung over the ground in front of the pedestrian. That makes it possible to preview the ground for about 1 m in front of the user and the space up to the level of the user’s waist, which provides information and warnings important for safe walking (Barth and Foulke 1979). In addition to being long, the canes are usually white in order to be more easily observed by other travellers.

In spite of its technical simplicity a long cane can inform its user of many features of the environment, such as location of objects, texture and hardness of the ground, bumps and drop-offs which might cause the traveller to fall. Additionally, it makes possible the detection of street crossings and the direction of kerbs; information that is helpful in the direct guidance of locomotion (Guth and Rieser 1997; Jansson 2000b). The haptic stimulus properties made available via the cane are based on vibrations in the cane and force feedback during the handling of the cane. There is also important auditory information, but that is outside the scope of this chapter (Schenkman 1985; Schenkman and Jansson 1986).

There are several practical requirements on such a simple device: for instance, it should conduct vibrations, have a good weight distribution, be lightweight but have sufficient weight to withstand breeze and be strong and durable. For convenience, many people want a collapsible cane, for which there are more requirements. The suitability of the cane tip and the cane grip also needs to be considered, as well as its visibility for other travellers (Farmer and Smith 1997).

It should be noted that it is significant for the usefulness of the long cane that it is handled in a proper way, and that the user has suitable training in its use (Zimmerman and Roman 1997). There are also special programmes developed for preschool children, older persons, as well as for learners with hearing, motor, cognitive and health problems in addition to vision problems; chapters describing these special training programmes can be found in the book edited by Blash et al. (1997).

In addition to the long cane, there are many technically simple arrangements that can be useful for the guidance of walking without sight: handrails, traffic sounds and sounding traffic lights (Guth et al. 1989; Guth and LaDuke 1994) and aids providing information about veering from an intended path via hearing (Gesink et al. 1996; Guth et al. 1996) or touch (Jansson 1995).

4.4.2 The Guide Dog

At first thought the guide dog for the visually impaired pedestrian may not be considered as a technical aid as the dog is a living creature. However, it may be thought of in that way. The dog and the person form a unit together with the uniting harness. This is a girdle encircling the dog’s chest with a handle for the

user. With the handle a visually impaired pedestrian both controls the guide dog and receives information about its activities. Haptics is thus important also for guide dog users.

Dogs for guiding visually impaired people were used thousands of years ago, depicted, for instance, on the walls of Pompeii. However, the systematic and widespread use of guide dogs started only after the First World War (Hännestrand 1995; Whitstock et al. 1997). As with the long cane, training is an important prerequisite for success. The puppy intended to be a guide dog is carefully selected and trained at special schools, and the guide dog user also has to be trained. Guide dogs are very important for many visually impaired people, but availability and cost restrict their use. It should also be clear that the guide dog, as the long cane, can be helpful for mobility in the near-space, but not for orientation in the larger environment. This information must come from other sources, both from environmental information and from the pedestrian’s memory.

4.4.3 Braille

A visually impaired person can read text either by listening to spoken text or using the hands to obtain a tactile equivalent. The former medium is often called talking book; the most common version of the latter medium is Braille. Letters and other symbols in Braille are coded within a six (or sometimes eight) point rectangular matrix that is presented in embossed form and read by the fingers (Foulke 1991). It is an invention that found its form during the early nineteenth century, and it has been a most important reading medium for the visually impaired since then. However, much training is needed to be a fluent Braille reader, which is why it is mainly used by people who are blind from birth or become blind at an early age. The main reason for the difficulties of many older people to learn Braille is that their tactual acuity is not as good as that of a young person (Stevens 1992; Stevens et al. 1996). However, the cited problems of older people in learning new skills, slower movements and quicker loss of memory may be unjustified and no obstacle to learning to read Braille in older age (see for example, Millar 1997, pp 239 ff ).

There is another embossed reading system, Moon, where the letter symbols are similar to ordinary letters and therefore can be read with less training, but this method is not very widespread. However, Moon text has been rendered to be used in connection with simulated tactile diagrams (Hardwick 2004). Technological devices for reading Braille have been developed and these will be discussed below; more discussion can be found in Chapters 12 and 14 of this volume.

A basic prerequisite for reading Braille is that the fingers can discriminate between the point patterns within the matrix. In order to facilitate this, strict rules for the properties of the point matrices have been developed and changes have to be carefully motivated. A thorough analysis of perceptual, linguistic and cognitive aspects of Braille reading was given by Millar (1997).

Many thought that Braille would disappear when the talking book arrived. However, that has not been the case, probably because it has features that the talking book does not have to the same extent, for instance, easier skimming of the text to locate specific parts.

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4.4.4 Embossed Pictures

Pictorial information can also be presented in embossed form. Edges and surfaces can be reproduced with embossed lines and patterns of embossed units, respectively. The idea of embossed pictures is quite old; such pictures were available in the eighteenth century (Eriksson 1998). They have not been used as widely as the long cane and Braille, in spite of much effort to make them useful (for example, see Edman 1992). Some kinds of pictures can be read without much difficulty (Kennedy et al. 1991) and it has also been reported that blind people can draw pictures (in two dimensions) of three-dimensional objects and scenes (Kennedy 1993). However, more complex embossed pictures are more difficult to perceive haptically, the main problem being to get an overview of the picture. Even if it is possible to get information with a “haptic glance”, as discussed above, identification is often obtained only after exploratory movements that can take considerable time and that sometimes do not result in an understanding of the picture. Further, tactile pictures are typically two-dimensional, and to get perception of three-dimensional properties of the scene haptically is usually difficult, even if some possibilities have been reported. Kennedy (1993) described the understanding of perspective by blind people, while Holmes et al. (1998) and Jansson and Holmes (2003) reported on the haptic perception of depth in pictures via texture gradients, one of the main features of visual 3D perception of pictures.

4.4.4.1 Techniques for Making Embossed Pictures

Originally embossed pictures were “applications”, that is, the embossments were obtained by gluing things like strings, cloths and other materials onto a paper or board. This method is still used to some extent, but it is an expensive method, as it is necessary to apply all material manually onto each picture. A method making possible the production of copies from one such manually made application is thermoforming, a method where a model in 3D is copied onto a plastic sheet. In a machine for this procedure the plastic sheet is put onto the model, heated and formed after the model when the air between the sheet and the model is removed. For the production of models, special kits of symbols considered useful for tactile reading have been developed, especially for maps (see, for instance, the work of James and Armstrong 1976 and Barth 1982).

In another method, heating to get embossment is also used – microcapsule paper or swellpaper. This kind of paper has a layer of microscopic plastic capsules that expand when heated. Black points, lines and patterns written or printed on the paper make the part of paper below them to emboss, while the rest of the paper remains non-embossed at proper heat exposure (see, for instance Edman 1992, pp 82–89). No heating is needed for raised line drawing boards. They consist of a thin plastic sheet fastened to some kind of firm backing. The embossment is obtained by writing with, for instance, a ballpoint pen on the sheet. This method is probably the most important method for visually impaired children’s drawings (see, for instance, Edman 1992, pp 15–17). Other methods, as well as more details