Prolonged exposure to wide field-of-view visual motion can cause visually-induced motion sickness (VIMS). Reports on which frequencies of visual motion that will provoke the highest levels of VIMS have been contradicting. An in-depth review suggests that these studies manipulated the frequency of their stimuli in different ways: some kept stimuli’s velocity constant while others kept stimuli’s amplitude constant. In other words, there may be two types of frequency responses for VIMS depending on whether the velocity or the amplitude of the visual motion was kept constant (referred to as the two-frequency-response hypothesis). In this thesis, four experiments were conducted to test the two-frequency-response hypothesis within the scope of visual motions along the fore-and-aft axi...[ Read more ]

Prolonged exposure to wide field-of-view visual motion can cause visually-induced motion sickness (VIMS). Reports on which frequencies of visual motion that will provoke the highest levels of VIMS have been contradicting. An in-depth review suggests that these studies manipulated the frequency of their stimuli in different ways: some kept stimuli’s velocity constant while others kept stimuli’s amplitude constant. In other words, there may be two types of frequency responses for VIMS depending on whether the velocity or the amplitude of the visual motion was kept constant (referred to as the two-frequency-response hypothesis). In this thesis, four experiments were conducted to test the two-frequency-response hypothesis within the scope of visual motions along the fore-and-aft axis. The first two experiments (Experiment PS1 and PS2) measured the illusive sensation of self-motion (vection) and perceived speed (PS), and the other two experiments (Experiment VIMS1 and VIMS2) measured VIMS directly. These experiments consistently found that there were two different types of frequency responses with VIMS, vection and PS. When the r.m.s. velocity was kept unchanged, the severity of VIMS was independent of frequency and when the amplitude was kept constant, the level of VIMS increased with increasing frequency. Based upon the findings of the experiments, a better method to simplify and unify the presentation of the two types of frequency responses of VIMS was proposed. Moreover, how the current findings relate and fit into the existing literature body was discussed, with an additional application to enhance a previously reported cybersickness dose value (CSDV) model for predicting levels of VIMS.