Evaluation of temporal relationship between a physiological index and a subjective score using average mutual information

Recently, because of the ubiquitous popularization of home video cameras, countless people have had opportunities to watch video images captured by amateur cameramen. Because of this, concerns have arisen over potential negative impacts on viewer health, such as visually-induced motion sickness (VIMS). To determine the mechanism inducing VIMS and to establish a method of preventing it, it is necessary to understand which types of video scenes are associated with the onset of VIMS. Furthermore, while it is useful to consider viewer self-assessments while watching such scenes, physiological indices can provide even more information because they can be measured second-by-second in real time. However, there is not much knowledge regarding the temporal relationships between the severity of VIMS and its accompanying physiological conditions. In this study, the average mutual information was employed to determine the temporal relationship between subjective evaluation scores (a subject's personal evaluation of his/her own condition) and various physiological indices present when people suffer from VIMS. Our analysis of experimental data found that changes in the two physiological indices, which were respiratory sinus arrhythmia and the maximum cross-correlation coefficient between heart rate and pulse transmission time, had a concordance rate of more than 60% with changes in the severity of VIMS symptoms experienced by test subjects. Furthermore, we determined that it may be possible to detect signs of impending VIMS prior to the development of symptoms by analyzing physiological indices.