Although binocular disparity and motion parallax are effective cues to depth, the effective ranges of these cues are not large. An excessive disparity or motion parallax causes the percept of diplopia or motion and degrades the apparent depth. However, simultaneous presentation of very large disparity and motion parallax causes a vivid depth perception with the percept of diplopia and motion. We compared the perceived depth for lateral head movement with that for sagital one to examine whether the facilitation of stereopsis depends on the direction of the observer's head movement. A small disk was presented 2.5 deg above or below the fixation point with disparity and/or motion parallax. Eleven observers estimated the depth of the target relative to the fixation point, Using a matching method. In experiment 1 the range of head movement was 13 cm. In experiment 2 the ranges of lateral and sagital head movement were 1.8- and 50- cm respectively, so that the ranges of stimulus motion were equalized to 1 deg. The results of these experiments showed that the facilitation occurs for lateral but not for sagital movement, suggesting that the facilitation of stereopsis is specific to the lateral stimulus motion.

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Changes in the passing speed of the self-projection object, i.e., the mouse pointer lead to a perception of a sense of inner force. This phenomenon is called pseudo haptics. The characteristic of pseudo haptics has been investigated for motion in the frontal parallel plane. We investigated the effect of motion in depth in 3D space on the perception of pseudo haptics. We found that incidence rate and perceived force of pseudo haptics in the depth direction are lower. Furthermore, pseudo haptics are affected more by visual perception than by arm exercise.

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When a sinusoidal grating (test) is abruptly displaced by a phase angle of 180deg synchronously with the 90deg shift of gratings (inducer) above and below it, the test appears to move in the same direction as the inducer (motion assimilation). To investigate temporal characteristics of the motion assimilation, stimulus-onsetasynchrony (SOA) is introduced between the displacements of the test and the inducer and the magnitude of motion assimilation was measured as a function of SOA. The effect of SOA on the magnitude of motion assimilation changed significantly as a result of changes in the spatial frequency of the test grating.

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