Palpable City is an extension of Tactile Space - a wearable interface to tactile landscapes, undertaken as part of my MS thesis project in Information and Computer Science in the
Arts, Computation and Engineering program at University of California Irvine, 2004 - 2005
Palpable City explores the relationship between the abstract and
concrete spaces of the city by parameterizing its spaces of
representationÐthe space of architects and urban plannersÐwith
phenomenal space, to challenge our "lust to be a viewpoint" [1] in
understanding the urban experience. The project allows walkers to feel
the spatial form of the urban grid at their location as vibro-tactile
rhythms on their body. The rhythms of the urban grid are parameterized
by local conditions as the walker encounters them, reflecting the
influence of time, light, temperature and humidity on the experience of
space. Augmenting the everyday activity of walking the city with a
tactile experience challenges participants to think about the
interrelation of vision and touch in their experience of space. The
void of purely optical space is thickened with palpable sensations,
creating a tactile space that can only be explored by moving through
it. Tactile displays are usually applied to provide orientation
information in unusual phenomenal environments, such as virtual
reality, deep sea diving, and zero gravity environments. In Palpable
City, this process is reversed; instead of providing a stable spatial
reference in unusual conditions, the technology is used to make the
usual experience of space unusual.
1. Michel de Certeau. The Practice of Everyday Life, "Walking the City."
from TactileSpace installation at UC Irvine
system
maps/sketches
technology
There are a number of tactile receptors that could be stimulated for
use in wearable computing applications: thermal, pressure,
electrocutaneous, humidity, air movement, vibrotactile, etc. The
current state of the art points to vibrotactile as the modality for
ubiquitous computing applications. Vibrotactile actuators are neither
intrusive nor painful (problems that are possible with electrocutaneous
actuators). They can be felt through clothing, are inexpensive, and
have relatively low mechanical and power requirements.
A perceptual illusion, sensory saltation, holds promise for use in
vibrotactile displays. Sensory saltation occurs across the senses
resulting in the perception of apparent motion. Tactile sensory
saltation was discovered in the early 1970s by Dr. Frank Geldard at the
Princeton Cutaneous Communication Lab. In a typical setup for eliciting
tactile sensory saltation, three mechanical stimulators are place
equidistant from each other on the forearm. The stimulator closest to
the wrist delivers three short pulses, followed by three more at the
middle stimulator, and finally three more at the last stimulator.
Instead of perceiving three pulses at each of the stimulator sites, the
observer perceives that all of the pulses are distributed with
approximately uniform spacing from the site of the first stimulator to
the site of the third. (Figure 2) The sensation is described as if a
tiny rabbit was hopping up the arm from wrist to elbow, and is
sometimes called the "rabbit" effect or the "cutaneous rabbit." (Figure
1) An important feature of this illusion is that it is able to simulate
higher spatial resolution than the actual number of stimulators, yet
create the impression of a dense stimulator array, thus potentially
reducing the overall weight and power consumption needs of a wearable
device.
Using variations in these parameters in different
spatio-temporal patterns has uncovered a group of concepts which can be
perceived through the tactile sense. For example, a single point can be
perceived as a direction. (van Erp, 2001) Tactors arranged spatially on
the body can create a relationship akin to vision where the ego center
is perceived as one point and the stimulus at another, thus creating
direction. Taking advantage of sensory saltation, lines can be
perceived, as can their length, straightness, spatial distribution and
smoothness. (Cholewiak, 2000) There is also some more recent research
(TNO Human Factors) that suggests planes and three dimension forms can
be perceived. Tactors on the body can create a 360 degree "field of
touch" where lines and forms can be perceived not just on the surface
of the body, but through the body. Finally, the tactile systems that
have been discussed are very easy for users to learn, and require
practically no training.
Figure 1: A Norwegian artist's illustration of the 'cutaneous rabbit'
|
background
tactile vision+haptic space arises out of concerns about the
ways in which new technologies shape our perceptions of space. The
computer arises from Western scientific ideology which is built upon
the assumption that the mind is separated from the body. The influence
of this assumption is present at all levels of the technology, from the
architectural level in the hardware/software split to the reduced set
of body senses/movements engaged by its interface. The majority of
research in human computer interaction has focused on the visual or
aural modalities. Very little has been focused on the cutaneous senses.
This could be because culturally, the senses of the flesh are regarded
as the most lowly, the most animal. They are the farthest away from
pure reason or thought, a belief upon which computing is founded: the
mind/body split. The mind/body split has been debunked time and time
again from all angles: philosophy, linguistics, biology, neurology,
cognitive science, art, and even computer science (Dourish). However,
embracing what embodiment means is difficult in a language that reifies
the ideology. We talk of "my hand" or "my head" as if they are objects
that we own, not inseparable parts of our being. To describe what is
meant by embodiment, we must use neologisms such as the embodied mind,
being-in-the-world, the life-world, etc. An embodied perspective that
is not clouded by traces of duality is difficult, at best, in
contemporary Western culture. In computer science, where the ideology
is ingrained in the technology itself, it presents an even stiffer
challenge.
As computing produces increasingly influential cultural
artifacts and becomes ingrained in culture, it can no longer disregard
the ideologies that have been responsible for cultural production for
the thousands of years of humanity's existence. The 'arts' (with a
lowercase 'a') have traditionally emphasized body knowledge in the
making of things. Embodied thought is important in the design of
physical spaces (architecture) as well as in the making of objects. As
computing begins to shape physical spaces and their uses, it will be
important to look to the arts and architecture to see where the
underlying assumptions inherent in the discipline conflict with
embodied humanity. tactile vision+haptic space combines technology and
the environment through embodied interaction.
Please refer to the written thesis for citations: [pdf]
© Erik Conrad 1998-2006
Figure 2: Graphical representation of the saltation illusion