The findings from the experiments in this chapter suggest that IVB's may be effective for reducing simulator sickness and simulator-induced ataxia. It is encouraging that strong effects were found in this initial work, using short exposure durations, a low-end HMD with limited FOV, and a simple manifestation of the IVB concept.
Rest frame selection appears to be a pre-conscious operation: we are not generally aware of how our perceptual system determines what will and will not be interpreted as stationary. Consequently, it may be possible to induce a visual rest frame which avoids motion sickness and simulator side-effects without impinging on attention, and thus distracting from the task at hand.
It is noteworthy that a significant decrease in total stance breaks (in both experiments) and SSQ ratings (in Experiment AIIIE1) was possible without a significant difference in vection ratings between conditions. In the experiments, we used a post- rather than per-exposure vection measure, to avoid an additional load on participants during trials. It is possible that a more sensitive per-exposure vection measure would have found a difference between the two conditions: this is an interesting topic for future research. However, we believe that current data are sufficient to indicate that there was not a large difference in vection between the two conditions. If one accepts that vection is related to the sense of presence in a virtual environment (see Chapter 3) this suggests that an IVB can produce performance and simulator sickness benefits without substantially reducing the sense of presence in a simulator.
The significant difference between pooled pre- and post-exposure ataxia scores in Experiment AIIIE2 is important, given that exposure durations were only 4.5 minutes per condition and only a low-end system was used. This is an indication of how easily VE's can produce after-effects. However, these after-effects seemed to disappear quickly: no difference was found for pre-exposure ataxia between the first and second conditions, with a 15 minute break before the second condition. Furthermore, subjects were required to perform at their baseline levels of postural stability before leaving the area. This occurred within 10 minutes after the second exposure for all subjects.
An improved use of the IVB might be to put it in the periphery of the display. In the current implementation, subjects often reported that they lost track of the visual background when focusing on the CI. Placing the IVB in the periphery might allow the IVB to be processed non-competitively and unobtrusively in peripheral vision. This is a topic for future research.