CHAPTER 6
Touch
ROBERTA L. KLATZKY AND SUSAN J. LEDERMAN
147TOUCH DEFINED AS AN ACTIVE, MULTISENSORY
SYSTEM 148
THE NEUROPHYSIOLOGY OF TOUCH 148
The Skin and Its Receptors 148
Pathways to Cortex and Major Cortical Areas 150
SENSORY ASPECTS OF TOUCH 150
Cutaneous Sensitivity and Resolution 150
Effects of Body Site and Age on Cutaneous
Thresholds 150
Sensory-Guided Grasping and Manipulation 151
HAPTIC PERCEPTION OF PROPERTIES OF OBJECTS
AND SURFACES 152
Haptically Perceptible Properties 152
Roughness 153
Weight 154
Curvature 155
Role of Manual Exploration in Perceiving
Object Properties 156
Relative Availability of Object Properties 158
HAPTIC SPACE PERCEPTION 159
HAPTIC PERCEPTION OF TWO- AND
THREE-DIMENSIONAL PATTERNS 160
Vibrotactile Patterns 161
Two-Dimensional Patterns and Freestanding Forms 161
Two-Dimensional Outline Drawings of Common
Objects 161
Three-Dimensional Objects 162
VISUAL-HAPTIC INTERACTIONS 164
Attention 164
Cross-Modal Integration 165
HAPTIC MEMORY 165
APPLICATIONS OF RESEARCH ON TOUCH 167
Aids for the Visually Impaired 167
Haptic Augmentation of Speech Perception 168
Teleoperation and Virtual Environments 169
SUMMARY AND FUTURE DIRECTIONS 169
REFERENCES 170This chapter describes a sensory modality that underlies the
most common everyday activities: maintaining one’s posture,
scratching an itch, or picking up a spoon. As a topic of psy-
chological research, touch has received far less attention than
vision has. However, the substantial literature that is avail-
able covers topics from neurophysiology, through basic
psychophysics, to cognitive issues such as memory and ob-
ject recognition. All these topics are reviewed in the current
chapter.
We begin by defining the modality of touch as comprising
different submodalities, characterized by their neural inputs.
A brief review of neurophysiological and basic psychophysi-
cal findings follows. The chapter then pursues a number of
topics concerning higher-level perception and cognition.
Touch is emphasized as an active modality in which the per-
ceiver seeks information from the world by exploratory
movements. We ask how properties of objects and surfaces—
like roughness or size—are perceived through contact and
movement. We discuss the accuracy of haptic space percep-
tion and why movement might introduce systematic errors or
illusions. Next comes an evaluation of touch as a pattern-
recognition system, where the patterns range from two-
dimensional arrays like Braille to real, free-standing objects.
In everyday perception, touch and vision operate together;
this chapter offers a discussion of how these modalities inter-
act. Higher-level cognition, including attention and memory,
is considered next. The chapter concludes with a review of
some applications of research on touch.
A number of common themes underlie these topics. One is
the idea that perceptual modalities are similar with respect to
general functions they attempt to serve, such as conveying in-
formation about objects and space. Another is that by virtue
of having distinct neural structures and relying on movement
for input, touch has unique characteristics. The chapter
makes the point that touch and vision interact cooperatively
in extracting information about the world, but that the two