Abstract
The stability zone refers to a zone between the concomitant-motion threshold and the depth threshold of motion parallax driven by head movements. In this zone, depth is seen but not motion (i.e., location constancy holds). Ono and Ujike (2005, Perception, 34, 477–90) determined the extent of the stability zone for a stimulus with four horizontal bands of grating. In their stimulus, the adjacent bands moved in opposite directions and the movement of the bands was slaved to the head movement. In this study, we measured the stability zone for stimuli with the four different velocity gradients examined by Rogers and Graham (1979, Perception, 8, 125–34). We found that a different stability zone exists for each gradient, although the sizes of the zone for stimuli with sine and triangle gradients were similar to each other. Moreover, the concomitant-motion thresholds for the stimuli with the sawtooth and square gradients were lower than those for the sine and triangle ones, and therefore the zones were smaller. This result suggests that stimuli with gradients that contain abrupt changes have smaller stability zones.
This research was supported by Grant A0296 from NSERC