Experiment AIIIE2 found that a strong effect for reduced per-exposure ataxia remained in the presence of a CI task. This was true even though the IVB was again rated as less visible than the CI (mean rating 2.5, with 1 indicating only the CI was visible, 7 indicating only the IVB was visible). This indicates that the IVB does not have to be overpowering to be effective.
There was a sharp drop in the overall ataxia for both conditions from Experiment AIIIE1 to Experiment AIIIE2 (See-through: 4.1 vs. 1.6; Occluded: 9.1 vs. 2.6). We hypothesize that this was due to the absence of head rolls.
The absence of head rolls, reducing overall effects, may partially explain the lack of a significant difference on the SSQ and SB1 vs. SB3 tests (which were significantly different in Experiment AIIIE1).