The effect of differences in viewing environment and method on physiological responses and perceptual stability while viewing three-dimensional images.

BACKGROUND: Stereoscopic (3D) viewing can induce motion sickness and visual discomfort under specific environmental conditions. Light adaptation is not always linear; preceding light exposure influences subsequent physiological responses (hysteresis). However, hysteresis in 3D viewing has rarely been studied. OBJECTIVE: This exploratory study examined whether physiological responses exhibit hysteresis-history-dependent asymmetries between increasing and decreasing illuminance phases-under combinations of low illuminance, color temperature, and viewing mode. METHODS: Eight healthy adults (age 21.75 ± 0.97 yr) were exposed to stereoscopic video under eight conditions (2 color temperatures × 2 illuminance-change directions × 2 viewing modes). Illuminance was varied in stepwise fashion (10-260 lx). Electroencephalogram (EEG; Fp1/Fp2), electrocardiogram (ECG), and Stabilometry were recorded. Repeated-measures ANOVAs with Benjamini-Hochberg FDR correction and paired Hedges' g effect sizes were computed. RESULTS: Large hysteresis effects were observed for postural sway (Hedges' g = 0.66-1.01) and moderate effects for theta-band EEG (|g| ≈ 0.5-0.65), particularly in peripheral vision under low illuminance. Stabilometry was significantly greater at 10 lx compared to higher illuminances (p < 0.05). The interaction between illuminance and illuminance-change direction was significant for total locus length per unit area (L/A) in peripheral vision under daylight color. CONCLUSIONS: Postural control, but not autonomic function, exhibited strong history dependence in response to illuminance changes during 3D viewing. Findings suggest minimum illuminance guidelines (∼80-100 lx) and consideration of illuminance-ramp rates for VR safety and 3D content design.