VR is the development of artificial environments that can be navigated directly. They can be the relatively simple or very complex. They fall into two general categories: window on the world and immersion. In window on the world, the user views the environment as from a window into the world. The monitor screen is the window and the information on the screen provides the visual information about this world. This is the type of VR involved in most video games and a very primitive version of this type of VR is illustrated in Figure 21. The more compelling and interesting type of VR occurs when the person is immersed in the environment. This type of VR uses helmet-mounted displays to generate the visual information, often has an integrated sound system, and occasionally provides tactile feedback. It is this latter type of VR that holds the most interest, but research and study is proceeding on both types of VR.
Figure 21. Here is a very primitive virtual environment of the window on the world type. Use the arrows to navigate to the right and the left and observe the movement of the two objects in the display. [Figure 21 description]
VR is both a research technique, because of its ability to provide sensory input from multiple sensory systems in a controlled manner, and a research area because it is also an application where sensory knowledge will be fundamental for success. Some examples of the application of VR that are relevant to psychology have been in clinical psychology (Huang, Himle, & Alessi, 2000; Jang, Ku, Shin, Choi, & Kim , 2000; Roessier, Mueller-Spahn, Baehrer, & Bullinger, 2000), neuropsychological evaluation (Kesztyues et al., 2000), memory research (Gamberini, 2000), and education and training (Cromby, Standen, & Brown, 1996; Mohler, 2000).
One of the research advantages of the most advanced VR systems is that it can provide controlled inputs to the visual, auditory and tactile systems. To date, the vast majority of studies in sensation and perception have primarily investigated the senses separately. However, many experiences are based upon inputs from multiple sensory systems. For example, hearing and seeing a bat hit a ball. Consider how jarring it is to sit so far away that the sound and the sight are not integrated.
The study of body orientation, for example, focuses on a fundamentally integrated sensory system. A series of recent studies suggest that visual information alone may be sufficient for determining whole-body translation and linear movement in the virtual environment. However, feedback from the tactile systems may be needed for accurate determination of rotation (Chance & Loomis, 1987; Richardson, Hegarty, & Montello, 1997).
Richardson et al. (1997) found that going around a staircase in a virtual building leads to larger errors in determining their location relative to their starting point than either learning the environment from maps or actually moving through the real version of the environment. Chance and Loomis (1987) studied perception of direction in individuals moving in virtual environments, with or without tactile feedback. Chance and Loomis found that if a person actually rotates but translates via the virtual environment, thus receiving the tactile input from the rotation, they kept their sense of direction far better. We know that visual input is suppressed during saccadic eye movements, which accompany body rotations. Perhaps the orienting system, not expecting good visual input during physical rotation, has developed a tendency to rely more on tactile input (Krantz & White, 1989; Volkmann, 1986) . The need to rely on tactile input may result from the fact that during the illusion of rotation in a VR environment, the vestibular system is not activated, an illustration of the importance of understanding the integration of different sensory systems (Cohn, Dizio, & Lackner, 2000). The VR environment is especially suited to studying multi-sensory and sensory-motor integration.
Sensory research is also proving to be helpful to engineers working on VR systems. In a recent paper, Cutting (1997) gives a review of the visual information needed for VR applications, including how space perception and the use of depth cues can assist VR engineers in developing appropriate visual inputs. An important feature of Cuttingís work is his quantitative approach to VR. Just as it was necessary to develop equations for color matching to be used in monitors and printing, so it will be necessary to provide quantitative functions for other visual functions before they can be applied to VR. Thus, research in sensation and perception may well take the form of taking well-understood phenomena and developing quantitative models for application.
This research may also indicate new visual functions that need to be explored. One possible issue is the location of the center of projection relative to the persons eye height. Dixon, Wraga, Proffitt, & Williams (2000) found that the relationship between a subjects eye height and the center of projection profoundly affected the perception of size.
Another interesting question related to VR that is both a research question and an application issue is the difference between the two forms of VR. The experience of VR in the immersion techniques is far more immediate than the window on the world. What are the features that makes this so? One difference is that the field of view tends to be far more restricted in the window on the world (Dichgans & Brandt, 1978) though Dixon et al. (2000) found that an immersion technique with a restricted field of view had as strong a relationship between eye height and perceived size as did a full immersion technique. The window on the world condition in the same paper showed now effect of the relationship between eye height and center of projects. These results suggest that the difference between the two forms of VR is more than just a difference between the size of the field of view. All in all, VR is a fruitful field for psychological research into sensation and perception and vice versa. In fact it appears that the development of VR and the use of VR as a research tool in sensation and perception may be tightly intertwined.