Biomedical Engineering Reference
In-Depth Information
her generally uphill course. After reaching the top of the hill, Sarah directs her gaze
down toward a larger river running below her before deciding to move on back to her
campsite. Even before her campsite comes into view, she can smell smoke coming
from the campfire that Brian had just built.
This brief vignette illustrates the variety and the complexity of information that is
available to people as they navigate through known and unknown places. In the story,
Sarah uses a variety of online sensory information—visual, kinesthetic, vestibular,
somatosensory, auditory, and even olfactory—to provide information about her envi-
ronment and her place in it. She is also able to use offline information—internally
stored knowledge—to determine her goals and destinations. Because nearly every
sensory modality can contribute information about one's spatial disposition or about
the spatial properties of one's environment, it is a challenge for scientists to under-
stand how this multimodal influx of information is acquired, interpreted, combined,
and acted upon. In this chapter, we will examine what is known about the different
ways that people can take-in the spatial information that is available to them as they
walk through real and computer-simulated (virtual) environments. In the first part of
the chapter, we will briefly discuss what we know about the senses' contribution to
spatial knowledge, including the circumstances under which each sense in isolation
is necessary or sufficient for acquiring spatial knowledge and for enabling spatial
behaviors. The modality-by-modality discussion, however, is only expository; it is
important to realize that in most real situations, information flows simultaneously
through all of the senses—that spatial information is multimodal, overlapping, and
heavily redundant. Thus, in the second part of the chapter, we examine situations
in which there are differing combinations of sensory information about space. In
particular, we discuss the sensory contributions of today's computer-simulated envi-
ronments, in which some sensory modalities have access to limited or imperfect
information.
Before we can begin a meaningful discussion of incoming sensory information,
we will do well to recognize that the issue of sensory contributions to spatial knowl-
edge cannot be disentangled from conceptualizations of the type of knowledge that
is produced. In general, the type of knowledge that one acquires about his or her
environment depends critically on the goals that one has for interacting with the envi-
ronment. On one hand, many goals are served exclusively by transient knowledge
of one's location and orientation with respect to important objects in the immediate
environment. In the situation above for example, Sarah did not need to recall the
location of her campground in order to track and admire a nearby bird. Tasks such
as speed, distance, and turn estimation, as well as online spatial updating (i.e., the
ability to track one's location and orientation with respect to salient objects in the
environment; see [
62
]) may involve a dynamic formof environmental knowledge that
consists of little more than sensitivity to ongoing changes in immediately available
information. Here, internal representations of the environment may be minimal—
fragmented, sketchy, and schematic—or even nonexistent, because the environment
itself provides easy access to necessary information. Such situations seem particu-
larly well addressed by concepts that have developed out of the ecological approach
