Two experiments examined the effects of relative movements of the head with respect to a stimulus display on the magnitude and direction of the perceived depth from motion parallax. In Experiment 1, a velocity gradient of random-dots moving in opposite directions was presented in three viewing conditions: (a) stationary head-and-display, (b) display-movement, and (c) head-movement. The observer's task was to report the direction and magnitude of the perceived depth. The results with 10 observers showed that the magnitude of the perceived depth in condition (b) was lower than those in conditions (a) and (c), while the direction was unambiguous in (b) and (c), but ambiguous in (a). In Experiment 2, the direction of the perceived depth was examined in six conditions including the three of Experiment 1; in the other three conditions both head and display were moving in the same direction but with different ratios of the display velocity to the head one: (d) 0.5, (e) 1.0, and (f) 2.0. The results with 11 observers showed that unambiguous depth perception was obtained in conditions (b), (c), and (f) but not in conditions (a), (d), and (e).Furthermore, the depth order perceptions in (b) and (a) were identical to those in (f), and (e), respectively. The experimental results suggest that relative movement of the head with respect to the display irrespective of either movement is processed to determine the perceived depth order and that the velocity gradient within the display is processed to determine the magnitude of the perceived depth.

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Tactile sensitivity of the foot was investigated using the Semmes-Weinstein monofilament method to quantify the pressure sensory threshold. Gender differences and variations in sensitivity at various sites on the foot (inter-locational sensitivity differences) were analyzed using a nonparametric test. Skin elasticity at 3 points on the sole was measured using a Venustron device (AXIOM Co.), and the relation to sensitivity was examined. Gender differences and inter-locational differences in plantar elasticity were also analyzed. Subjects were 53 male and 31 female volunteers aged between 18 and 39 years who had no known neurological dysfunction or disease. Results showed no significant gender differences in foot sensitivity but indicated significant inter-locational sensitivity differences (p<0.01). A typical pattern was observed in the distribution of sensitivity, with the dorsal region being the most sensitive, followed by the plantar arch and the side region (lateral, medial and back regions), whereas the plantar region other than the plantar arch was the least sensitive. Weight bearing locations appeared less sensitive than sites that do not bear appreciable weight. Inter-locational differences with respect to skin elasticity was significant (p<0.01), with the center of heel point being hardest, followed by the plantar arch point, while the 1st metatarsal head point was softest. Although we anticipated that pressure sensory thresholds might be estimated from elasticity, the correlation between these two factors was too low to enable this. The plantar region has different sensitivity and elasticity characteristics depending on the sites of the sole and on the individual. Shoe comfort may be improved by adjusting the properties of materials forming the insole to the sensitivity and elasticity characteristics of the individual foot.

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