Psychology of Touch and Blindness

Morton A. Heller, Edouard Gentaz

• Publisher: Psychology Press
• Year: 2013
• Print ISBN: 9781848726536
• eBook ISBN: 9781134521661
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

This book reviews the considerable body of research that has been done to evaluate the touch skills of blind people. With an emphasis on cognitive and neuroscientific approaches, it encompasses a wide-ranging discussion of the theoretical issues in the field of touch perception and blindness.

The volume includes chapters on sensory aspects of touch, perception in blind individuals, multimodal relations and their implications for instruction and development, and new technology, including sensory aids and virtual touch. A distinctive feature of the book is the inclusion of the practical applications of research in this area.

A significant characteristic of research on touch and imagery in congenitally blind individuals is that it speaks to the basic nature of spatial imagery and the importance and necessity -- or lack thereof -- of specific visual sensory experience for the acquisition of knowledge about space, spatial layout, and picture perception. As such, the book will not only appeal to researchers and professionals with an interest in touch and blindness, but also to a wider audience of cognitive psychologists and cognitive neuroscientists working in the field of perception.

1 Introduction

Historical and Philosophical Background

Touch is a remarkable sense and is unique in a number of ways. It allows us to experience an amazing and wide variety of sensations. Some of these are delightful, but some are really unpleasant. Information derived from touch is essential for our survival, and the world would be a very dull place without the pleasures that we experience using our sense of touch.

Touch comprises sensory and perceptual elements, and both will be discussed at length in this volume. As a sensory system, we can feel hardness, softness, and a number of primary qualities of objects (Locke, 1689/1975). These primary qualities are important for a number of reasons, but we would be hard pressed to survive without the ability to “feel” our surroundings. Touch also imposes a number of sensations that can have emotional impact, and these differ in many ways from the sorts of sensations that we can experience through olfaction, gustation, or vision. It is difficult to imagine the “feel” of the odor of a rose, for example. Conversely, I cannot conceive of how one can truly “visualize” the pain induced by an abscessed tooth in need of a root canal.

Touch has many remarkable qualities as a perceptual system, and these will be emphasized in this volume. While such topics as pain will be covered, more discussion time will be devoted to the perceptual aspects of touch.

The organ of touch is unique in comparison with the other senses. Our sense of touch is dependent upon our skin, obviously the largest sense organ we have. In addition, touch sensibility is dependent upon the musculature and underlying tissues. The touch “organ” continually changes in shape, and this is radically different from other sense organs. Our eyes are relatively constant in configuration, as are our other senses. Of course, the nose changes somewhat as one “sniffs” and the eyes may squint or narrow. However, these changes are not nearly as dramatic as the changes that generally occur in body configuration. The variability of the structure of the sense of touch is a strength of the haptic perceptual system, but this also represents a practical challenge to researchers.

We feel things with our hands, but we obviously can feel with all of our body components. I can feel the floor beneath my feet as I walk, and I feel the chair that I sit on. For example, while eating corn on the cob, I can feel it with my mouth (teeth, tongue, and lips) and both hands. While I generally ignore the feeling of clothing on my skin while engaged in other activities, I am sure that I would notice it if my clothes were to suddenly vanish while teaching a class!

Much of the study of touch has involved the hands, although many developmental researchers have been interested in oral touch. Infants spend considerable time “mouthing” objects and sucking on them (Bushnell & Boudreau, 1991). However, we feel objects with all parts of our bodies during the course of a day. I can feel my dog brush up against my calf, for example, and I can feel my leg against my desk as I write this manuscript. Physical contact with the world is a perceptual background that is always present, whether or not we devote much conscious attention to this perceptual experience.

Historical Background

Interest in the sense of touch has a number of important roots, including philosophy, clinical neuroscience, cognitive neuroscience, psychophysics, engineering, and, of course, the important consequences of a lack of touch sensibility in diabetic neuropathy. Of great interest has been the impact of visual loss on how we rely on the senses, particularly the sense of touch.

Clinical Roots

Diabetes may all too often cause a loss of vision, and is a very common cause of blindness. It also may lead to neuropathy, and a loss of touch sensation in the hands and feet. These sensory losses can promote peripheral damage to organs. It is all too easy for a person to damage the skin, if he/she cannot feel how pressure is applied when manipulating objects. A similar loss of tactile sensation occurs with leprosy.

Very dramatic tactile sensory loss can take place with spinal damage. Morton Heller has known an individual who was paralyzed and also suffered sensory loss from spinal damage owing to trauma from penetrating wounds. This person developed bedsores and died of infection at a relatively early age. It is difficult to survive when mobility and touch sensations are severely compromised.

Brain damage can often yield unfortunate clinical symptoms, and these are apparent in alterations in touch. People may experience chronic pain. Inappropriate pain experiences can be related to alterations in one's body image, as in phantom limb pain (Critchley, 1953). Here, a person feels pain in a limb that has been amputated. Furthermore, peripheral neural damage can yield pain experience, when one might expect to feel normal touch. These protopathic pain sensations can cause considerable distress. Also, people with fibromyalgia feel pain upon light touch to the skin, and this can make them miserable.

Central nervous system damage can produce alterations in tactile perception that can be very disturbing. People may feel phantom limbs where no limb has ever existed (Critchley, 1953). These symptoms involving a body image disorder can occur along with epileptic seizures or by themselves. For example, some individuals may feel an arm coming out of the middle of their chest and even feel it wiggle.

Jonathan Cole described the case of Ian Waterman, who suffered a complete loss of tactile sensation over his entire body below the head (Cole, 1995). This extremely rare neurological disorder may have developed from a viral infection. Whatever the cause, Waterman collapsed when trying to stand up one morning. He was unable to move or feel anything. The impact of the loss of touch was devastating. He had to learn, over a relatively long period of time, how to use his sight to control movement of his limbs and manipulate his body. The loss of touch can be deadly, since tactile and pain sensations serve to preserve us by warning of danger. The sense of touch is often ignored by many of us, and we take it for granted. We would not take touch for granted if we were unable to feel anything. Loss of tactile sensation can also derive from causes that do not involve neural damage. While not very common today, many of Freud's patients presented with glove anesthesia, where they had a loss of sensation on both of their hands, as if wearing gloves. Fortunately, leprosy is now rare in the United States and Europe but still occurs in third-world countries. The disease compromises tactile sensation in the face and extremities. Without the ability to sense pain or pressure on the skin, it is all too easy to inflict damage on oneself.

People can learn to compensate very effectively for a loss of vision or of hearing. While none of us who rely on sight or hearing wants to go blind or deaf, people may live relatively “normal” lives without sight. Blind people shop, travel, and do all of the things that the rest of us do. One can argue that they may benefit in some ways from an inability to “watch” television. However, some tasks that we accomplish using sight are more difficult to do with touch. Reading Braille is slower than reading with one's eyes, and society does not make things very easy for people who are visually impaired. Walking in traffic is fraught with danger for any of us, but the danger is increased for people without sight.

There are some striking differences between the operation of touch and vision, and this has complicated our understanding of the sense. Of course there are similarities, and these will be discussed in this volume. Touch is intimately linked to movement. Unlike vision, haptic examination of a surface or object can alter it. Haptic refers to an active exploration of objects using intentional action (Gibson, 1962). For example, if one picks up a cat or dog and strokes it, this action changes the visible and tangible configuration of the object. Certainly, looking at one's dog can alter its behavior and induce some transformation in the configuration. But if one feels a person's face, this action alters the flexible aspects of the object, namely the muscles and skin. The underlying skeletal structure is not altered, assuming the mouth is not opened or closed. If one feels an object that is flexible or malleable, the shape of the object changes. Looking at another individual or object never produces precisely the same sort of transformation.

Blindness

Researchers have come to this research area because of theoretical and practical concerns about the impact of blindness on individuals. The loss of sight poses a number of problems for people, since they have to learn new mobility and communication skills. Blind people must show increased reliance on the sense of touch, and they provide a unique study sample for interested researchers. Blind individuals may have been born without any sight, and these congenitally blind (CB) persons reveal the ability of touch to perceive forms or object characteristics without the influence of visual experience or visual imagery. Most sighted individuals spontaneously report producing visual images while they feel objects. Some even indicate that they spontaneously close their eyes behind blindfolds while engaging in haptic exploration of pictures or maps. Moreover, people who lost their sight later on in life, the adventitiously blind, or late blind (LB), also say that they can remember how things look and may experience visual images while they feel objects (Heller & Ballesteros, 2006).

Many researchers have assumed that the presence or absence of visual imagery is critical and has a great influence on haptic perception in blind individuals. For example, Lederman, Klatzky, Chataway, and Summers (1990) explicitly assumed that touch is best at perceiving the material qualities of objects, namely hardness, softness, weight, and so forth. Geometrical properties, they argue, are more appropriately perceived via sight, and touch requires visual mediation in order to judge form most adequately. Note that it is easy to recognize familiar objects by touch (Klatzky, Lederman, & Metzger, 1985). Indeed, if one could not identify familiar objects by touch, this would be a sign of significant brain damage (Critchley, 1953). One might expect that visual imagery and visual mediation would be lacking in CB individuals. Consequently, this may explain some reports of lower performance by CB persons in picture naming tasks (Heller, 1989a). This issue will be taken up at greater length at a later point in this volume, but there is a large amount of literature showing the benefits of visual imagery for memory in sighted individuals (Paivio, 1965). However, it must be noted that there are many differences in the backgrounds of CB persons and other individuals besides visual imagery and visual experience. Educational experience differs as a function of vision or lack of it, as does prior experience with tangible pictures. The use of 2-D illustrations is often lacking in the educational background of many blind people. It is entirely possible that deficiencies in the education of people who are visually impaired, rather than an absence of visual imagery or visual experience per se, plays an important role in the data that are present in the research literature.

There are important applied and practical concerns in the area of blindness rehabilitation. Blind people require instruction in the use of touch for mobility, reading, and communication. The consequences of early versus late onset of blindness have implications for rehabilitation and education. If an individual loses sight at birth or in early childhood, there may be reduced opportunities for learning about some academic areas, such as mathematics or geography. This is the case because tangible illustrations are infrequently available in text material. However, the CB child has probably had considerable education in mobility and a lot of experience with using touch for pattern perception involving Braille. People who lose their sight later in life or in old age are unlikely to be willing or motivated to undertake the considerable time and effort required for learning these important skills. Furthermore, increased practice using the sense of touch for pattern perception in blind individuals could explain their superior performance in a number of tactile spatial tasks (Sathian, 2000). Sighted individuals certainly use the sense of touch while wielding objects or manipulating them. It would be impossible to drive if one could not feel the steering wheel as one drives a car down the road. However, sighted individuals more often use touch to manipulate objects, rather than for pattern perception. We most frequently rely on our vision to make judgments about object geometry, spatial relations in the world, mobility, and for reading and using computers. It is in these sorts of tasks that blind individuals have increased experience using the sense of touch.

Pictures have played a minimal role in the lives of most blind people in the United States, and many other places in the world. The frequent assumption has been that pictures are for sighted people, but not for individuals who are blind (Heller, 2000a). Heller has heard more than one blind person say “ … you are trying to make blind people think sighted” in the midst of a research study (p. 757). This negative attitude about the value of pictures for blind people may derive from a general bias within our society and the educational community. Whatever the source, negative expectations tend to be self-fulfilling prophecies and may compromise the interpretation of the results of research in this area. The practical implications of a lack of exposure to pictures and illustrations can involve disastrous limitations in educational experiences for blind individuals. This issue will be taken up at a later point in this volume.

A number of theoretical perspectives have assumed that haptic perception is not capable of good performance in the perception of tangible pictures. If this were true, it would require a very negative prognosis for the value of pictures in the rehabilitation of blind people, and for their understanding of space. However, the research literature suggests greater optimism than older research in the area would suggest (Heller & Ballesteros, 2006; Heller et al., 2009).

Philosophical Roots

The study of touch has a number of philosophical antecedents, and this chapter will not attempt an exhaustive examination of them. However, the present state of knowledge and research in the field has been greatly influenced by the work of philosophers, and this background should be discussed.

Rock and Harris (1967) described Bishop Berkeley's purported claim that touch educates vision over the course of development. Visual images change apparent size as one approaches or moves away from an object, and visual angle becomes an unreliable clue to size or distance for unfamiliar objects. Thus, if infants lack innate knowledge of how to interpret what they see, and cannot judge size and distance accurately, how are they to know whether the changing image of a parent who is approaching is growing larger, or is actually approaching? Berkeley discussed the notion that we learn to interpret visual images by way of an association with our own movement and mobility in the world. However, Berkeley (1709/1974) argued that we never really “see” distance, since it is an intellectual sort of judgment, rather than a perceptual judgment. Thus, we come to learn that the smaller image size of a person at a distance means that the person is far away, but we do not directly “see” this.

Philosophers have long been interested in blindness and what it can tell us about perception and the relationship between vision and touch. John Locke (1632–1704) was particularly interested in William Molyneux's (1656–1698) question (a letter sent to JL on 7 July 1688; cf. Morgan, 1977; Wade & Gregory, 2006), namely what would happen if a person who was born blind suddenly had sight restored? Thus, if a person who was limited in life to feeling a cube and sphere and never saw them, suddenly had vision restored, would the person know how to name these objects upon first seeing them? Would the individual immediately know how to interpret what she or he saw, or would learning be required? The empiricist response from Locke is that learning would be needed. However, one might think that some simple aspects of the geometry of objects, namely curvature or angles, would be comprehensible from a nativist perspective, emphasizing innate processes.

Gregory and Wallace (1963) have provided important insights into this issue in their description of an individual who had sight restored in middle age. Richard Gregory's description indicated that many aspects of visual space were incomprehensible to this middle-aged person after surgical restoration of vision. Depth, perspective, and other aspects of our typical visual experience were confusing. The restoration of sight was of little benefit to a person who was competent as a blind person, but not functional as a sighted one. Important visual perceptual skills were lacking, including visual object recognition, reading, and visual skills related to mobility. Thus, restoration of sight turned a well-adjusted competent (blind) person into one who was illiterate and had great difficulty functioning in the world as a sighted individual. The surgical intervention was not very helpful to this person. Indeed, one older CB individual once told Heller that if it were possible to restore his sight, he wouldn't want to do it. He was functioning perfectly fine in the world and did not relish the idea of this sort of radical transformation. Just as sudden blindness late in life can be difficult to cope with, the reverse can be true as well.

Marius von Senden (1960) described a large number of cases of the restoration of sight. Unfortunately, it is difficult to know how to interpret many of them. A typical case involved cataract surgery, but earlier methods dating to von Senden's time did not provide clear indications about an answer to Molyneux's question. After cataract surgery, an individual's vision was not normal for some period of time, since the older procedures were very crude and required large incisions, substantial trauma, and a long recovery period. Large incisions were required for cataract surgery more than 15 or 20 years ago. In addition, it was often the case that the examination of patients occurred a considerable time after restoration of sight. Currently, cataract surgery may lead to excellent vision on the same day as the procedure, but surgical advances have been dramatic over the past few years.

Weber, Katz, and Revesz: Historical Roots

Ernst Heinrich Weber has had a significant impact on current thinking and research on sensory processes in touch, despite the fact that much of his work dated from 1830–1850 (Weber, 1978). His description of sensory circles anticipated current thinking on receptive fields. Weber's research was modern and timeless.

Weber made a number of interesting observations and empirical c...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Acknowledgments
• 1 Introduction: Historical and Philosophical Background
• 2 Cognitive Neuroscience of Touch
• 3 The Haptic Perception of Objects and Their Properties
• 4 Illusions
• 5 Intermodal Relations
• 6 Development of Haptic Perception Over the Life Span
• 7 Blindness: General Introduction: Pattern Perception, Imagery, Spatial Orientation, and Mobility
• 8 Picture Perception and Blind People
• 9 Braille and New Technology
• 10 Haptics in Learning Reading, Handwriting, and Mathematics
• 11 Tactile Interfaces and Applications
• 12 General Conclusions: Implications of Current Research for Theory and Applications
• References
• Author Index
• Subject Index