Here's a good article which was posted on the Easi list. I haven't
looked yet to see if the cited researchers have web pages and
accessible journal articles.
----- Forwarded message begins here -----
From: James A Ansley <jansl@world.std.com>
To: EASI@MAELSTROM.STJOHNS.EDU
Date: Wed, 22 Jul 1998 17:00:41 -0400
Subject: touch-perception research
I thought that the attached article on touch-perception research might be
of some interest or utility to list members.
Jim Ansley
_________________________________________________________________
Copyright 1998 by The American Psychological Association
APA Monitor
VOLUME 29 , NUMBER 6 -June 1998
_________________________________________________________________
From surgery to robotics, touch is the key
Researchers probe how people learn about objects through their sense
of touch.
By Beth Azar
Monitor staff
Surgeons performing microscopic surgery rely on visual cues from a
video screen to determine the best place to make an incision, place a
sponge or insert a suture. They have none of the tactile cuesthe feel
of a wiry vein, the edge of a muscle or the softness of tissuethat
they have performing traditional surgery.
In large part, thats because the design of instruments that give
surgeons tactile input is in its infancy. Engineers and computer
scientists are working on the problem, but truly effective tactile
simulators wont be available until researchers can answer some basic
questions about how people perceive touch, says psychologist Susan J.
Lederman, PhD, of Queens University in Ontario, Canada.
She and her colleagues are trying to provide those answers. She
oversees Queens Universitys Touch Laboratory and has collaborated for
more than a decade on studies of touch with Carnegie Mellon University
psychologist Roberta Klatzky, PhD.
Together, Lederman and Klatzky have amassed data on how people learn
about objects through touch and what kind of information they obtain.
Theyve also begun to team up with engineers to determine whether touch
input is important for jobs such as operating robots from afar and
performing microscopic surgery.
'If you dont understand the capabilities and limitations of humans,
you cant design systems that permit them to operate effectively on
remote environmentswhether they be real or virtual,' says Lederman.
Research on hands
Research on the haptic sensory system focuses mostly on the hands
because the fingertips contain one of the highest densities of tactile
receptors, says Klatzky.
'The same kinds of explorations could be formed with other limbs or
with the mouth,' she says. 'But the hands provide the dexterity and
sensitivity we need for our experiments.'
Some of their earliest work set out to determine how people learn
about objects with their hands. They found that people use six basic
'exploratory procedures':
Lateral motionrubbing the fingers across a surface provides
information about an objects texture.
Pressurepressing down on an object provides information about its
hardness.
Static contactholding the fingers in one spot, provides information
about an objects temperature.
Unsupported holdingholding an object out away from a support provides
information about its weight.
Enclosurewrapping the hand around an object provides information about
its global shape and volume.
Contour followingmoving the fingers about the perimeter of an object
provides information about an objects exact shape.
People perform these procedures in a logical pattern: First they grasp
the objecta quick, crude way of gaining a lot of initial information.
Then, if necessary, they begin to use the specialized hand movements.
These findings provide a basis for understanding how people
intelligently explore objects, says Lederman. And if engineers want to
design robots that can use tactile sensors to analyze an environment,
they will need to devise systematic manual testing procedures that,
when sequenced appropriately, will extract tactile information
effectively. A robotic hand may not use the same exploratory
procedures a human hand usesits sensors may be differentbut engineers
can use Lederman and Klatzkys findings to develop their own version of
procedures the robots can use.
Materials, not geometry
Psychologists research is particularly key to working on systems that
enable humans to work in remote or inaccessible environments, such as
microsurgery, radioactive sites and even other planets. Engineers must
understand which tactile properties people are most attuned to.
Over the years, research findings converge on the principle that touch
is extremely sensitive to material propertieshow hard, cool, pliant
and rough an object is. But the sense is relatively poor at
determining spatial and geometric properties, such as whether an
object is sloped to the right or left, or whether an edge is
horizontal or vertical.
Indeed, in a recent series of studies published in the Journal of
Experimental Psychology (Vol. 23, No. 6, p. 16801707), Lederman and
Klatzky found that people process geometric and spatial properties
much more slowly and less accurately than material properties or the
presence or absence of edges. Furthermore, the brain can search for a
material property with six fingers simultaneously but must search for
a spatial target one finger at a time, the researchers found.
These findings suggest that engineers should design tactile interfaces
that provide information about materials and edges rather than
geometry, whenever possible.
'Tactile interface designers shouldnt expect people to read fine
patterns with their hands,' says Lederman.
However, people will quickly and easily respond to tactile cues such
as surface texture or sharp edges. Indeed, adding texture or
edge-orientation cues, rather than labels, to dials on a car radio
could reduce the need for people to look down to change the station,
says Klatzky.
The importance of force
Because the haptic system is so complex, adding tactile information to
remote-access devices is a daunting prospect for engineers. So its up
to psychologists to convince them theres value in adding tactile
feedback to instruments, says Lederman. She and Klatzky have
preliminary evidence hinting that feedback does provide a certain
advantage.
They tested peoples ability to perform several tasks with and without
feedback to their index fingers. The tasks were chosen to represent
situations that people might encounter when using a remotely operated
instrument. For example, they measured peoples ability to feel
vibrations; to sense whether they can feel two distinct objects or
just one; and to detect the presence of a thin nylon hair. They also
tested perceptual abilities, including the ability to judge how rough
a surface is and to compare the roughness of two surfaces. And, they
assessed peoples ability to detect a rigid mass embedded in simulated
tissue.
To simulate a no-feedback situation, the researchers covered
participants fingertips with a rigid fiberglass sheath. The sheath had
a dramatic impact on several aspects of sensitivity and perception,
Klatzky and Lederman found. Peoples ability to sense the thin hair
declined by 73 percent and their ability to detect two objects as
opposed to one declined by 321 percent. They also lost the ability to
tell whether two objects were oriented in the same direction and had
far more trouble detecting a mass embedded in tissue.
'The results suggest there may be significant perceptual costs when
spatially distributed fingertip forces are not sensed or displayed to
novice operators of teleoperator and virtual environment systems,'
write Lederman and Klatzky. Their article is in press in Presence, the
Massachusetts Institute of Technologys magazine on research related to
virtual reality.
Maximizing perception
The key to designing more useful virtual environments and teleoperator
devices is to supply people with a blend of sensory information, says
Lederman. In the real world, people tend to integrate information from
all their senses rather than operate with one sense at a time.
'For example, touch and vision complement each other,' says Lederman.
'They do different things very well.'
While vision provides information about an objects geometric features,
touch is unparalleled in its ability to extract information about
materials. For a surgeon trying to decide where to begin excising a
patch of cancerous tissue, it might be helpful to feel the texture and
compliance, and not just rely on the shape.
__________
End of document
------ Forwarded message ends here ------
-- Lloyd Rasmussen
Senior Staff Engineer, Engineering Section
National Library Service for the Blind and Physically Handicapped
Library of Congress 202-707-0535
(work) lras@loc.gov http://www.loc.gov/nls/
(home) lras@sprynet.com http://home.sprynet.com/sprynet/lras/
This archive was generated by hypermail 2b29 : Sun Dec 02 2012 - 01:30:04 PST