The following research questions were posed at the top of Chapter 5:
Experiment AIIE1 and Experiment AIIE2 found the predicted effect of a foreground occlusion increasing reported presence. While this result is to be expected from the vection literature, it appeared to come as a surprise to most virtual environments researchers at the time. These experiments served the twin purposes of supporting the hypothesized link between vection and presence and of pointing out an application of foreground occlusions to HMD design.
The literature and pilot study reported in Appendix E point to another application of foreground occlusions to HMD design, besides increasing presence. Foreground occlusions may also be useful to reduce binocular rivalry for displays with a partial overlap between the scenes displayed to the two eyes.
Appendix C reports on a series of studies which sought a performance measure for foreground occlusions, in terms of a spatial orientation task. While two pilot studies were promising, the full experiment (AIIE3) failed to find an effect. Possible modifications to Experiment AIIE3 are discussed in Appendix C. However, based on current data, it appears doubtful that the foreground occlusion effect will be successfully measured with experiments similar to AIIE3.
Given the subjective strength of the foreground occlusion effect (as measured in Experiments AIIE1 and AIIE2) it would be surprising if it could only be detected by self-report measures. The search for a foreground occlusion performance measure might pursue a spatial task which more clearly requires a switch of the selected rest frame away from the laboratory and into the scene shown on the display. However, it is not immediately clear what an appropriate task would be. Alternatively, an attempt might be made to measure the foreground occlusion effect with a nulling measure.