by Jerrold Prothero
Chapter to be published in forthcoming book:
L. Hettinger and M. Hass (Eds). Psychological Issues in the Design and the Use of Adaptive, Virtual Interfaces
Two fundamental issues facing the virtual interface community are avoiding motion sickness and developing robust measures for the goodness of virtual interfaces (in terms of their intuitiveness and their ability to convey meaning). Both of these issues go to the core of human psychology; hence it is unlikely that they can be addressed effectively except through a fundamental psychological theory. Synthesizing prior work in many areas of perception, such a theory is put forward.
Literature is reviewed indicating that presence, the sense of "being in" a virtual interface, is related to the intuitiveness and meaningfulness of the interface. Therefore, Class A ("objective") presence measures are potentially useful to evaluate these aspects of virtual interfaces.
The following two hypotheses are advanced, which suggest that presence plays a deep role in perception, and is closely related to specific visual illusions, as well as to motion sickness.
These hypotheses suggest three areas of research. Prior and future work in each of these areas is described.
This suggests "Class A" measures for presence based on creating a conflict between virtual and real rest frame cues and measuring their relative influence on perception.
The nervous system uses particular cues from the environment to select a rest frame. By manipulating these cues, it is possible to affect the sense of presence in a virtual environment. (There are also potential applications to facilitating task performance by communicating particular rest frames, for instance in the context of collaborative work in weightlessness.)
A. Suggests links between presence and various illusion such as vection, induced motion, perceived tilt and distance illusions, all of which can be categorized in terms of how they might arise from rest frame disturbances. The common themes between them are summarized (for a brief discussion, see Appendix).
B. Suggests links between presence, motion sickness, and the illusions mentioned in "A". Hence, techniques can be borrowed from the literature on these illusions to address motion sickness, and in particular the form which occurs in simulators.
SRF's are hypothesized to determine one's sense of position, angular orientation and motion: both for oneself and for objects in the environment. This implies that SRF failures should result in illusions of position, orientation, and motion.
We would expect the visual background to play an important role in determining the SRF, since the visual background in general provides the largest set of self-consistent motion cues in the environment.
If we consider the crossing of ``self'' or ``external objects'' with ``position'', ``orientation'' or ``motion'', we would predict that six types of illusions should be possible by altering the SRF through visual background manipulations. The six possiblities are itemized below.
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Howard, I. (1986). The perception of posture, self motion, and the visual vertical. In Handbook of Perception and Human Performance. New York, NY: John Wiley & Sons.
Levine, M. & Shefner, J. (1991). Fundamentals of Sensation and Perception. Pacific Grove, CA:Brooks/Cole Publishing Company.
Ohmi, M., Howard, I.P. & Landolt, J.P. (1987). Circular vection as a function of foreground-bakcground relationships. Perception, 16, 17-22.
Ohmi, M. & Howard, I.P. (1988). Effect of stationary objects on illusory forward self-motion induced by a looming display. Perception, 17, 5-12.
Wallach, H. (1959). The perception of motion. Scientific American, July.