Experiment AIIIE1 was the initial study of the effectiveness of an IVB for reducing simulator side-effects. A low-end system was used, comparing the see-through (IVB) and occluded (non-IVB) modes of a Virtual i-O HMD. A circular vection stimulus was provided in both conditions. Illumination levels were such that the IVB was rated by participants as being less visible than the vection stimulus. It was hypothesized that the IVB condition would produce lower simulator side-effects than the non-IVB condition.