Fwd: touch-perception research

From: Lloyd G. Rasmussen (lras@loc.gov)
Date: Fri Jul 24 1998 - 05:43:08 PDT


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