Is Depth Perception of Stereo Plaids Predicted
by Intersection of Constraints, Vector Average or Second-order Feature?
Louise Delicato and Ning Qian, Vision Research, 2005, 45:75-89.
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paper (PDF file).
Stereo plaid stimuli were created to investigate whether depth
perception is determined by an intersection of constraints (IOC) or
vector average (VA) operation on the Fourier components, or by the
second-order (non-Fourier) feature in a pattern. We first cre- ated
stereo plaid stimuli where IOC predicted vertical disparity, VA
predicted positive diagonal disparity and the second-order fea- ture
predicted negative diagonal disparity. In a depth discrimination task,
observers indicated whether they perceived the pattern as 'near' or
'far' relative to a zero-disparity aperture. Observers' perception was
consistent with the disparity predicted by VA, indicat- ing its
dominance over IOC and the second-order feature in this
condition. Additional stimuli in which VA predicted vertical dis-
parity were created to investigate whether VA would dominate
perception when it was a less reliable cue. In this case, observers'
performance was consistent with disparity predicted by IOC or the
second-order feature, not VA. Finally, in order to determine whether
the second-order feature contributes to depth perception, stimuli were
created where IOC and VA predicted positive hor- izontal disparity
while the second-order feature predicted negative horizontal
disparity. When the component gratings were oriented near horizontal
(±83 from vertical), depth perception corresponded to that predicted
by the second-order feature. However, as the components moved away
from horizontal (±75 and ±65 from vertical), depth perception was
increasingly likely to be predicted by an IOC or VA operation. These
experiments suggest that the visual system does not rely exclusively
on a single method for com- puting pattern disparity. Instead, it
favours the most reliable method for a given condition.
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