Information Technology Reference
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Figure 1.
the phone, and where, to an extent, the human
user can adapt, in order to create and appropriate
closed-loop behaviour. (See Figure 1).
There is already a wide variety of sensing and
display technologies that can be used to construct
the physical aspects of a human-computer inter-
face, and much recent research has been dedi-
cated to expanding the sensing and display capa-
bilities of typical devices. Rich sensors, from
accelerometers, smart clothing and GPS units, to
pressure sensors, create the potential for whole
new ways of interacting with computational de-
vices in a range of contexts. Each of these has
different information capacities, noise properties,
delays, power demands, frequency responses, and
other modality-specific characteristics. Sensors
will continue to get cheaper and smaller, and new
ones will create as yet unimagined interaction
possibilities. Building interfaces that make use of
possibly high-dimensional, noisy, intermittently
available senses to create usable communication
media is a significant challenge for the current
HCI framework. We need general frameworks
which are not tied to specific sensing or display
devices, but generalise to wider classes of de-
vices.
The display in any human-controlled control
system is to provide the user with information
needed to exercise control, i.e. to predict the
consequences of control alternatives, to evaluate
the current status and plan future control actions,
or better understand the consequences of recent
actions. Current examples of basic feedback loops
include: Visual, audio, or vibrotactile display of
the states of phone, or of distant events, people
or systems.
In a mobile context users are subject to sig-
nificant levels of disturbances and tend to have a
lower attention span, leading to fragmentary or
intermittent interaction. Because of this, in many
cases it can be advisable to use modality schedul-
ing , where the order of presentation of information
in different feedback channels can be controlled
as a function of the context, and the user's control
behaviour. Perception is commonly seen as process
of receiving information from the world, which
is typically followed by cognitive processes and
then action. However, in reality, perception is
tangled up with specific possibilities of action,
so perception is not mediated by action-neutral
models. Inner states are 'action-centred'. Gibson
called this detecting 'affordances'. Such affor-
dances are nothing other than the possibility for
use, interpretation and action offered by the local
environment to a specific type of embodied agent.
Perception is not passive reception of infor-
mation—it is geared to tracking possibilities for
action. Traditional actions on a mobile phone
consisted of button pushing, but in a modern phone
the action might also include gesturing with the
phone, tapping the phone, walking or driving to
a new location, changing the phone's compass
bearing. Some of these are essentially discrete
actions, but many others are actions which are
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