Anecdotal reports suggest that motion sickness may occur among users of contemporary, consumer-oriented head-mounted display systems and that women may be at greater risk. We evaluated the nauseogenic properties of one such system, the Oculus Rift. The head-mounted unit included motion sensors that were sensitive to users' head movements, such that head movements could be used as control inputs to the device. In two experiments, seated participants played one of two virtual reality games for up to 15 min. In Experiment 1, 22% of participants reported motion sickness, and the difference in incidence between men and women was not significant. In Experiment 2, motion sickness was reported by 56% of participants, and incidence among women (77.78%) was significantly greater than among men (33.33%). Before participants were exposed to the head-mounted display system, we recorded their standing body sway during the performance of simple visual tasks. In both experiments, patterns of pre-exposure body sway differed between participants who (later) reported motion sickness and those who did not. In Experiment 2, sex differences in susceptibility to motion sickness were preceded by sex differences in body sway. These postural effects confirm a prediction of the postural instability theory of motion sickness. The results indicate that users of contemporary head-mounted display systems are at significant risk of motion sickness and that in relation to motion sickness these systems may be sexist in their effects.

The spatial magnitude of standing body sway is greater during viewing of more distant targets and reduced when viewing nearby targets. Classical interpretations of this effect are based on the projective geometry of changes in visual stimulation that are brought about by body sway. Such explanations do not motivate predictions about the temporal dynamics of body sway. We asked whether the distance of visible targets would affect both the spatial magnitude and the multifractality of standing body sway. It has been suggested that the multifractality of movement may change with age. Separately, previous research has not addressed the effects of target distance on postural sway in older adults. For these reasons, we crossed our variation in target distance with variation in age. In an open-air setting, we measured standing body sway in younger and older adults while looking at visual targets that were placed at three distances. The distance of visual targets affected the spatial magnitude of body sway in younger adults, replicating past studies. Target distance also affected the spatial magnitude of sway in older adults, confirming that this relation persists despite other age-related changes. Target distance also affected the multifractality of body sway, but this effect was modulated by age. Finally, the width of the multifractal spectrum was greater for older adults than for younger adults, revealing that healthy aging can affect the multifractality of movement. These findings reveal similarities and differences between the spatial magnitude and the multifractality of human movement.

We exposed standing men and women to motion relative to the illuminated environment in a moving room. During room motion, we measured the kinematics of standing body sway. Participants were instructed to discontinue immediately if they experienced any symptoms of motion sickness, however mild. For this reason, our analysis of body sway included only movement before the onset of motion sickness. We analyzed the spatial magnitude of postural sway in terms of the positional variability and mean velocity of the center of pressure. We analyzed the multifractality of postural sway in terms of the width of the multifractal spectrum and the degree of multiplicativity of center of pressure positions. Results revealed that postural sway differed between participants who later reported motion sickness and those who did not, replicating previous effects. In a novel effect, postural responses to motion of the illuminated environment differed between women and men. In addition, we identified statistically significant interactions that involved both Sex and motion sickness status. Effects were observed separately in the spatial magnitude and multifractality of sway. The results were consistent with the postural instability theory of motion sickness (Riccio and Stoffregen in Ecol Psychol 3:195-240, 1991) and suggest that Sex differences in motion sickness may be related to Sex differences in the control and stabilization of bodily activity.

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We sought to evaluate changes in subjective experience and postural performance among older adult passengers during the first 2 days of a sea voyage. On a vacation cruise, volunteer passengers gave verbal ratings of subjective bodily stability and awareness of ship motion followed by performance on the tandem Romberg test while facing fore-aft and athwartship. Data were collected when the ship was at the dock and on each of the first 2 full days at sea. Ship motion reduced subjective bodily stability and performance on the Romberg test and increased awareness of ship motion. On the first day at sea, Romberg performance was more strongly impacted by motion of the ship in roll (i.e., when facing fore-aft) than in pitch (i.e., when facing athwartship). Also on the first day at sea, subjective bodily stability