Psychophysics of Stereopsis                 (02/11/08 SS)
 
 
1. Principles
-Distance and depth
    Make a clear distinction between:
    absolute distance (between observer and object) &
    relative distance, or depth (between or within object(s))
-Depth “cues” and “common” representation
    Taxonomy: static vs. dynamic, monocular vs. binocular,
       physiological vs. pictorial, etc.
    Generic representation of depth based on various cues?
    cf. Transfer of depth contrast(simultaneous/sequential;  
         Graham, M. & Rogers, B. 1982)   
    cf. Stimulus convergence and response convergence
         (A. Yonas)
-Horopter (Vieth-Mueller’s circle)
    defined by fixation points for a constant vergence angle.
    This determines “zero” disparity.
-Binocular disparity
    =lateral displacement of retinal images between the
      eyes, caused by depth in the real world.
-Binocular vision (fusion vs. rivalry), determined primarily
     by correlation between the two eye’s inputs.
     cf. Helmholtz’s stereogram(opposite contrast between
          the halfimages)
-Scaling by distance
     Given a disparity, depth is correlated with distance2.
 
 
2. Classical stereogram & classical theories
-Stereoscope (Wheatstone’s & Brewster’s)
-Stereoacuity as a hyperacuity (both in order of several min.
    in the normal adult)
-“Pseudoscopic” perception, or integration of cues
-Contour-based theories (eg. Ogle)
 
3. Julesz' Random-dot stereogram & stereo as a module
-“Purely cyclopean” (cf. Fodor “modularity”)
-Early, and bottom-up
-Ambiguity solving and the “ghosts”(-->4)
-Binocular correlation (random-dot correlogram)
-Hysteresis
-Flexibility
-Filling-in and surface formation
 
4. Constraints
The stereo mechanism implements constraints to solve the
correspondence problem. = THE computational belief.
-Uniqueness
   D. Weinshall’s special case of violation.
-Order(“shallow slope”)
   J. Foley’s nail illusion.
   D. Jones & J. Malik’s computational model.
-Smoothness
   G. Mitchson & S. McKee’s spatially repeated stereogram.
 
However, do not forget that the correspondence solving is not the final goal. --> Depth assignment is the final (see the following sections).
 
 
5. DaVinci Stereopsis (K. Nakayama & S. Shimojo, 1989)
-Is interocular correspondence really necessary for stereo?   
     No. (cf. slit view)
-Depth perception and illusory occluding edge by
  “unpaired” stimulus (Da Vinci stereo).
 
6. Development of stereopsis and the “eye of origin”
-Is 3D perception innate?  Yes, and No.
-Pre-stereoptic binocular vision and the onset of ocular-
 dominance segregation à constrains the onset of stereopsis  
 at about 4-months of age in the normal human infant.
 
7. Adaptation and plasticity of stereopsis
-Stereo adaptation (cf. Graham & Rogers, mentioned
    above).
-Adaptation to exaggeration or reduction of disparity;
    occurs in order of minutes or hours (Brown, Wallach, 
    etc.)
-Adaptation to the reversal of disparity? (S. Shimojo & Y.
    Nakajima, 1980)
-Paradox about Anisometropia; the patients do not suffer 
    artificial tilt in depth (which is expected from the optical
    distortion) until they are tested with stereoscope.
 
8. Evolution of stereopsis
- In ancient nocturnal mammals? Replacement of motion
    parallax? (J. Pettgrew’s speculation)
- Anatomically different projections from the two eyes in
    birds -> an example of convergence of evolution.