The Psychology of Touch

Morton A. Heller, Morton A. Heller, Morton A. Heller, William Schiff, Morton A. Heller, William Schiff

• Publisher: Psychology Press
• Year: 2013
• eBook ISBN: 9781317760092
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

Designed to make research on touch understandable to those not specifically involved in tactile research, this book provides broad coverage of the field. It includes material on sensory physiology and psychophysics, thermal sensibility, pain, pattern participation, sensory aids, and tactile perception in blind people.

While the volume is important for researchers in the area of touch, it should also prove valuable to a broad audience of experimental and educational psychologists, and health professionals. The book should also be of interest to scientists in perception, cognition, and cognitive science, and can be used as a supplementary reader for courses in sensation and perception.

CHAPTER 1

INTRODUCTION

Morton A. Heller

Winston-Salem State University

This book is about the sense of touch. Our coverage here runs from details of physiology to matters of communication, cognition, and representation. The psychology of touch includes cutaneous sensitivity, kinesthesis, and haptics. The term haptics incorporates both cutaneous and kinesthetic information (Revesz, 1950). Through haptics, we obtain information about objects by actively manipulating them, with covariant cutaneous and kinesthetic input (Gibson, 1966). The 1980s saw vigorous theoretical debate and challenging empirical findings on touch and the range of perceptions it allows. We will survey contemporary thought on these issues. In some instances, the discussion of the evidence and resolution of controversial issues will await later sections of this book. I beg the reader’s indulgence in this matter, and urge patience. The interested reader will take a rewarding intellectual journey through the chapters within this volume.

Touch may involve ways of perceiving and representing reality that many people once thought were the exclusive preserve of vision or audition. Only in recent history have people tried to use touch as a channel for reading, speech signals, pictures, and music (via vibration). Some of these ventures have been amazingly successful.

The hand is a remarkable instrument, but it is not the exclusive organ of the sense of touch. If sensations were the source of perceiving, as many have explicitly and implicitly argued, then we can experience tactile sensations with our entire skin surface. If, on the other hand, touching is a set of activities yielding various sorts of information regarding the structure, state, and location of surfaces, substances, and objects in the environment, we use many sorts of haptic information to guide our activities. The feet, for example, make use of textural information about surfaces while we walk on them. Think of the difficulty one has walking on slippery ice. We change our stride in response to changes in friction, surface texture, hardness, and temperature. Blind pedestrians make use of haptic information from a long cane as they move about in the world. The lips are marvelous instruments for acquiring information regarding form, substance, and perhaps intention, and are a major source of shape information throughout life. Critchley (1971, p. 118) shows a photograph of a blind child reading braille with his nose. This is a further indication of the utility of other skin surfaces for pattern perception. We all rely rather heavily on tactile input over much of our skin while engaged in many perceptual activities. This reliance on the sense of touch often goes unnoticed, but rather than diminish its importance, it should stimulate wonder as to how limited our studies of touch have been.

We may become aware of our dependence on the sense of touch when something causes it to malfunction, and only then do we recognize its significance. Neither the leper nor the victim of diabetes doubts the importance of tactile input. Touch serves to warn us about impending or immediate danger, for example, via pain sensibility. In addition, our ability to maneuver in and explore the world as we do requires tactile input. This is obvious when we observe the relearning process as astronauts first walked on the moon. Even sitting utilizes tactile information, if only to tell us to shift our position. Our reliance on touch often goes unnoticed because of attention to visual perception, and because we tend to think of the performatory role of the hand rather than its sensing function (Gibson, 1962, 1966). We use our hands to obtain tactile information as well as to manipulate objects. However, much of our tactile input comes from parts of the body other than our hands (see Stevens, 1990). The tendency to identify touch primarily with the hands, and the close linkage between performance and perception, may have contributed to this bias.

The historical lack of interest in formally and seriously studying touch should be mentioned. Traditionally, psychologists have tended to emphasize the study of visual pattern perception when trying to resolve epistemological issues. Much of visual research has focused on attempts to understand pattern recognition via form perception. For example, more than a thousand experiments have been performed on visual illusions such as the familiar Müller-Lyer arrows. The sense of touch does not seem to operate as efficiently as vision in detection of outline forms. Touch is far slower, typically scans sequentially, and has a far more limited “field of view.” This has led many researchers to think of touch as less important than sight–a more primitive mode of perceiving that plays handmaiden to vision. We should also note that the postulated dominance of vision and audition is only recent, and that historically, touch has been regarded as dominant. Moreover, many would say that touch is still dominant, at least in terms of an existence proof for objects, that is, we test the reality of a mirage or dream image by trying to touch it.

This book has much to offer vision researchers and general students of psychology. It asserts that the investigation of touch is important and valuable. Few of us are willing merely to look at our world. Our lives would be short, indeed, if we could only look and not touch; many species would surely vanish. More to the point, many of the most important events in our lives involve the sense of touch. Touch has a powerful affective component as well as a cognitive one. We feel pain and pleasure, and these seem essential to existence. One can’t conceive of human life devoid of the sense of touch. Imagine one’s entire skin surface always under anesthesia! Rollman provides a detailed discussion of pain in his chapter in the present volume.

Moreover, the cognitive/affective components of tactile experience seem different from visual experience. We can readily feel that something is hot or cold, soft or hard, rough or smooth, in addition to its spatial attributes. Further, we can feel the sensuality of a very smooth piece of walnut, and the cold, impersonal hardness of steel. A splinter prompts intense emotional reactions that we would do well to attend to, as does immersion of the fingers in sticky substances of unknown origins.

While we depend on our sense of touch, some persons rely much more heavily than most on tactile input. Blind people use tactile information for reading and writing braille, for inspecting maps, and for much of their spatial cognition. Deaf-blind people are even more dependent on tactile information, since they also lack acoustical contact with the world. Touch provides information for friction, motion, and speech patterns. The individual with multiple handicaps and spinal injury may be almost completely limited to tactile input. In his provocative fictional book, “Johnny Got His Gun,” Dalton Trumbo (1970) described the plight of a veteran who lost almost all sensory input owing to physical trauma; Johnny could neither hear, nor see, nor speak, but learned to communicate with a nurse by tapping out Morse code with what little remained of his head. The nurse was able to talk to him by printing messages on the skin of his chest with her finger (pp. 197–199). The deafblind individual may make use of print-on-palm (POP) to communicate with people who are unfamiliar with manual signing, namely sighted and blind persons (Heller, 1986). Three chapters in this volume discuss perception and drawing in blind adults (Heller, Kennedy et al.) and children (Millar).

WHAT AND WHY VISION RESEARCHERS SHOULD KNOW ABOUT TOUCH

If all senses worked exactly like the visual system, it might not be as important to study the nonvisual senses. We could learn all about perception by just studying vision. The problem is not nearly so simple, however. Many aspects of objects and space can be known equally well through vision or touch, but some cannot (see Warren & Rossano, this volume). Very fine textures or surface variation, for example, are accurately perceived by touch, even when vision fails (Heller, 1989a). Moreover, we can often feel a splinter (to our discomfort!) when the same object is not visible without optical magnification. Touch may be especially suited for perception of such object characteristics as hardness, or softness (see Lederman & Klatzky, 1987) or substances within substances (e.g., grit in food or motor oil). Some aspects of thermal conductivity may be revealed only via touch. The chapter by Stevens provides a discussion of thermal sensation. Of course, we may also gain information regarding the hardness of surfaces by seeing or hearing events involving them.

In addition, touch and vision may not always operate in the same fashion (see Day, 1990; Over, 1968). Some researchers have emphasized limitations in touch, primarily because of the sequential nature of processing (Revesz, 1950; see Balakrishnan, Klatzky, Loomis, & Lederman, 1989). More recently, however, researchers have demonstrated word superiority effects in reading braille (Krueger, 1982b). The effect refers to the faster and/or more accurate detection of a particular letter in a word than in a nonword. As we shall see, this is a current theoretical issue, which is considered in the chapter on reading braille by Foulke.

While vision and touch may yield some equivalent percepts, it is in the realm of sensory experience where differences appear most obviously. There is no doubt that affective reactions are aroused by sight. Many of us have experienced the uplifting emotion elicited by a sunset, a waterfall, or other natural panorama of great beauty. We all have known the emotional impact of the sight of a very attractive person. The affective consequences of touch differ rather dramatically from sight, but are worthy of investigation in their own right. This has prompted the study of tactile sensations and sensitivity. Cholewiak and Collins discuss tactile sensitivity and physiology in their chapter. Rollman provides an interesting account of pain sensibility, in terms of both theory and application.

Finally, it should be pointed out that researchers interested in touch have studied many of the same theoretical issues that have directed research in vision and other areas. Research on touch may provide converging evidence on some very knotty theoretical problems. Tactile research has some unique advantages for the study of basic theoretical issues. Touch is well suited for the investigation of the role of revelatory movement in perception, that is, of what changes in stimulus information are revealed by active manipulation. It is easy to immobilize or control movement of the hand, but such control is at best arduous for sight, unless you limit the field of view as through a slit. However, we should note that the greater mechanical inertia of the hand (versus the eye) may make the hand easier to control and study, but it also makes the hand much more clumsy for the observer. In addition, tactile research permits us to study the relations between vision and another sense. Berkeley (1709/1974, p. 302) claimed that “the ideas of space, outness, and things placed at a distance are not, strictly speaking, the object of sight.… I neither see distance itself, nor anything I take to be at a distance.” He suggested that we learn to associate visual and auditory experiences with tangible ideas. This sort of discussion has led some individuals to believe that touch educates vision and audition (e.g., Diderot). Workers in motor behavior have been interested in the influence of visual guidance on skilled performance for some time. Visual guidance can aid touch through the provision of redundant information, and by fine-tuning movement so as to optimize information pickup. Visual guidance of the hand can help one cope with pattern tilt while trying to identify braille (Heller, 1989c).

THEORETICAL ISSUES

Much of the research in touch has been directed toward solution of fundamental theoretical issues. These are the same issues that have proven themselves so difficult for philosophers over many generations. The work encompasses research in perception and cognition, as well as fundamental sensory phenomena. If we examine the general experimental and vision literature (e.g., Kimble, 1990; Townsend, 1990), we find a concern with many of the same issues discussed by authors of chapters within this book. The issues will be described in this chapter, and a more thorough assessment of our current knowledge will be presented in the chapters in this volume.

Intersensory Equivalence

Can the senses of vision and touch give us the same information about objects and events? Is this information obtained automatically, or are translation mechanisms necessary? One version of the empiricist tradition holds that the senses are originally separate and must learn to treat information as equivalent. We may accomplish this when we learn to, say, attach the same response or label to something we touch and feel (see Revesz, 1950). Recent research on memory, especially that assuming an information-processing approach, has tended to stress modality differences. The information-processing view explains cognition by assuming our mental apparatus generates “icons,” or modality-specific, literal representations of stimulus configurations.

Gestalt psychologists tended to emphasize the notion that we obtain equivalent structures from the modalities of vision and touch (see Marks, 1978). Gibson’s ecological view (1966) has favored amodal percepts, that is, the notion that perception typically transcends modality-specific sensory experience. Attention to atypical sensations, and subjective phenomena such as pain or cold, lead us to notice the differences between modalities. Thus we see color, but feel pain. When we identify objects, however, it may matter little which sense obtains the relevant “information.” Warren and Rossano’s chapter is concerned with intermodal relations, especially the relationship between vision and touch.

Representation: Visual Imagery, Cognition in the Blind, and Tactile Imagery

Many researchers have been interested in the nature of representation. Revesz (1950) has suggested that sighted individuals tend to visualize when they feel objects in the dark. Introspection of the sighted might lead one to believe that visual experience is important for the development of spatial understanding. This problem has been approached through the study of the sense of touch in the blind (see chapters by Heller, Kennedy et al., and Millar, this volume). Late blind people remember how things look, and retain the ability to represent space in terms of visual images. Congenitally blind people must use the sense of touch for spatial representation. If congenitally blind people use imagery, one would expect that their images must be tactual. Some researchers have compared sighted and blind people’s performance on tactile tasks, with the aim being an evaluation of the nature of tactile imagery. This will also provide us with information about vision and visual imagery, should differences appear (see Heller, 1989b, this volume). However, we can’t rule out the possibility that congenitally blind people have visual imagery, but do not know what to call it. It is conceivable that we may eventually learn how to access visual imagery in these individuals.

It is theoretically possible, of course, that tactile imagery could provide much the same sort of information as visual images. However, should we discover differences in spatial cognition that could be specifically related to the nature of touch, we might begin to learn how best to structure instruction for the visually impaired. These questions about the nature of representation are clearly linked to issues of intersensory equivalence. Millar’s chapter is concerned with the nature of representation in touch.

There can be little doubt that learning plays a major role in the development of tactual skills. One need only observe a person who is skilled in the use of this sense, using braille, or a long cane, to realize the tremendous role that learning must play. Of course, this complicates any examination of the role of representation. The late and early blind may possess sophisticated skills (e.g., reading braille) that go untapped in some experiments.

Development of Touch and the Nature/Nurture Issue

Do the senses alter in relative importance over the life span? Does development change the relative importance of different body sites for information pickup? One might think, for example, that children spend more time and rely more on oral tactile input during the first year of life (see Ruff, 1989). Moreover, some researchers have argued that the senses are originally organized separately, and we come to coordinate information from different modalities through active movement. The intersensory integration notion proposes that we come to treat material from the senses as equivalent as a result of associative learning.

How important is learning for the sense of touch? A related issue has questioned the role of nature versu...

Table of contents

• Cover Page
• Half Title page
• Title Page
• Copyright Page
• Dedication
• Contents
• Preface
• 1 Introduction
• Part I: Sensory Phenomena
• Part II: Development and Intermodal Relations
• Part III: Tactile Pattern Perception
• Part IV: Tactile Perception in the Visually Impaired
• Author Index
• Subject Index