Levels of VR sickness

To improve VR systems and experiences, we must first be able to properly compare them in terms of their adverse side effects. Thus, the resulting symptoms need to be quantified. Rather than a simple yes/no response for each symptom, it is more precise to obtain numbers that correspond to relative severity. Several important quantities, for a particular symptom, include

• The intensity of the symptom.
• The rate of symptom onset or intensity increase while the stimulus is presented.
• The rate of symptom decay or intensity decrease after the stimulus is removed.
• The percentage of users who experience the symptom at a fixed level or above.

The first three can be visualized as a plot of intensity over time. The last one is a statistical property; many other statistics could be calculated from the raw data.