Depth from shading and disparity in humans and monkeys
Ying Zhang, Peter H. Schiller, Veronica S. Weiner and Warren M. Slocum
This study compared the effectiveness
of binocular disparity and shading cues for the perception of depth in humans
and monkeys. Using a novel display, we presented shading and disparity cues
conjointly, separately, and in conflict with each other in an oddities depth
discrimination task. An example of the figures used in the display appears in
the form of an autostereogram below. The following is a summary of our findings:
1. Both shading and disparity cues are effectively utilized for the perception
of depth by humans as well as by monkeys.
2. Depth information can be processed very rapidly when shading and disparity
cues are provided conjointly. When presented singly, the processing of disparity
cues takes significantly longer than the processing of shading cues.
3. By placing shading and disparity cues in conflict with each other
we assessed their relative effectiveness. Processing times were significantly
increased under conflict conditions suggesting that normally these cues are
co-processed. Similar values were obtained in humans and monkeys.
4. Control conditions for shading included the rotation of the display
by 90 degrees thereby reducing the effectiveness of differential luminance values
as a depth cue. Performance under these conditions became significantly worse
and reaction times were increased.