Abstract
Recently (VSS 2002), I reported that, when two stimuli are suddenly presented at different depth positions, the nearer stimulus tended to be perceived as presented later than the presentation of the further stimulus. In this study, I investigate whether the perceptual delay for the nearer stimulus is common for any events that happen at different depth, or it is restricted to the perceived time order for sudden presented stimuli. In order to compare with the results for the sudden presented stimuli, as an event at different depth. I used the stimulus shift by 1.4 arc min on front-parallel planes. Pair of mirrors and displays were arranged as a haploscope to present binocular disparity. The viewing distance to the displays was about 45 cm. Two vertical line stimuli (20.8 × 1.4 arc min) were presented at the same level (56 arc min above a fixation point that was located on a display surface) but different depth position by using disparity of 5.8 arc min. There were three conditions for depth location of the stimuli; one of the stimuli was nearer than the fixation plane by a crossed disparity of 2.9 arc min, or both stimuli were nearer (further) than the fixation plane by crossed (uncrossed) disparities of 2.9 and 8.7 arc min. There were nine SOA conditions for the shift of the two stimuli, ranging from −64 msec to 64 msec by 16 msec step (positive SOA indicates that the shift of the nearer stimulus was earlier than that of the further one). Each condition was presented 40 times in random order. Observers judged which stimuli shifted later in each trial. The perception of the shift for the nearer stimuli was delayed only when both stimuli were further than the fixation point. This indicates that the perceptual delay for the nearer stimulus would depend on not only the location of the stimuli, but also the type of events in three-dimensional space. How the time order in visual perception of stimuli located in three-dimensional space is determined would be discussed.