The Relationship between Spatial Velocity, Vection, and Visually Induced Motion Sickness: An Experimental Study

Spatial velocity (SV), a product of scene complexity and navigation velocity, is a metric to quantify virtual scene movement for the study of visually induced motion sickness (VIMS) (So et al., 2001). As SV increases, VIMS increases, peaks, and then decreases. Watching VIMS provoking stimuli of similar SV is hypothesized to produce similar levels of vection and VIMS. An experiment was conducted to test the hypothesis. Ten participants were exposed to five visual motion oscillating along fore-and-aft axis at different frequencies (from 0.05 to 0.8Hz). The r.m.s. velocity was kept constant and the frequency changes were achieved by changing the amplitudes of oscillation. These five stimuli had similar SVs. To our surprise, participants reported significantly different vection as the frequency increased even though the SVs were kept the same (p < 0.001). Levels of VIMS was not significantly different because the exposure duration was too short (20 seconds). A second experiment using stimuli with 30 minutes was conducted. Preliminary results indicated that levels of nausea significantly changed when viewers were exposed to visual oscillations with similar SVs but different frequency. Modifications to the previously reported SV metric are proposed.