Seeing many depth planes simultaneously

• Online Access: http://hdl.handle.net/2047/d20000670

Depth perception allows us to navigate a three dimensional world. To enable depth perception, our visual system uses several depth cues, one being stereopsis. Stereopsis results from the fact that humans have two forward-facing eyes that receive different views, which are then combined into one cohesive image with depth. By programming displays with multiple disparities, multiple transparent depth surfaces can be created with each disparity applying to a fixed number of stimulus elements (Random Dot Stereograms; RDS). Transparent refers to more than one depth surface in the same local area of the visual field, like leaves on a tree. Using RDS displays, Wilcox et al (2008) has shown that up to 6 depth planes can be reported almost perfectly with unlimited viewing time. However, unlimited viewing time permits multiple eye movements, so an impression of depth can be built up over time even if only 2 or 3 depth planes can be seen at once. We therefore re-ran her experiment with viewing time limited to 400 ms, a display time that made the display appear and disappear before an eye movement could be made, to see how many depth planes can be seen simultaneously (Semlow & Wetzel, 1979; Satguman et al, 2009). We also asked if people could see depth from opposite-contrast images (i.e. black dots corresponding with white dots). According to Harris & Parker (1995), this is not possible. Supplementing previous research (Wilcox et al, 2008), the findings demonstrated that the human visual system, under optimal conditions and after learning, is capable of perceiving 6 or more depth planes simultaneously. Contrary to the findings by Harris et al (1995), the human visual system is capable of acquiring depth information (up to 6 depth planes) within stimuli with same and opposite contrasts. We have found that the learning necessary to successfully distinguish these novel depth displays in adults is slow and progressive, possibly resembling the learning of depth cues in infancy.