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GEOMETRIJA VIZUELNOG PROSTORA Powered By Docstoc
					VISUAL SPACE ANISOTROPY
IN FULL-CUE AND
REDUCED-CUE CONDITIONS
Oliver Tošković
Faculty of Philosophy, Kosovska Mitrovica;
Laboratory for Experimental Psychology, Belgrade, Serbia
VISUAL SPACE GEOMETRY
   Blumenfeld and Hillebrand:
       parallel alleys lie inside distance alleys
    VISUAL SPACE GEOMETRY
   Luneburg – perceived                     x
    space is Riemannian
    space (with constant
    Gaussian curvature)
       Points on a Vieth-Müller
        circle are being perceived
        as equidistant from the
        observer

       Hyperbolae of Hillebrand     y   L       D

        are being perceived as
        radial lines of constant
        direction
    VISUAL SPACE GEOMETRY
   Luneburg – perceived
    space is Riemannian                      x
    space (with constant
    Gaussian curvature)
       Points on a Vieth-Müller
        circle are being perceived
        as equidistant from the
        observer

       Hyperbolae of Hillebrand
        are being perceived as       y   L       D

        radial lines of constant
        direction
    VISUAL SPACE GEOMETRY
   Luneburg – perceived
    space is Riemannian                      x

    space (with constant
    Gaussian curvature)
       Points on a Vieth-Müller
        circle are being perceived
        as equidistant from the
        observer

       Hyperbolae of Hillebrand
                                     y   L       D
        are being perceived as
        radial lines of constant
        direction
PHYSICAL vs PERCEIVED SPACE
   Herman von Helmoltz:
       Difference between physical and perceived horopter
       Change in perceived horopter with distance

                                horopter


           L


           R
PHYSICAL vs PERCEIVED SPACE
   Koenderink, J. Cuijpers, R.
    perception of parallelism     distance perception




           observer
    MOON ILLUSION
   Ptolemy – apparent distance
   Alhazen – moon illusion as a
    psychological phenomenon
   Rock and Kaufman
    – apparent distance theory         physical dome

    – flattened sky dome

                                   perceived dome
                                                Standing         Lying

                                                y=0.69x
                                                                   y≈ x


                                                             x
   Tošković (2004)            Indoor                                       x

       distance perception
   Elliptic model of                                        a                  b
    visual space
                                                y=0.73x
    (anisotropy)                                                 y=0.74 x
       Phisically shorter
        vertical distances =                                 x                      x
                               Outdoor
        longer horizontal
       Vertical distances
        are peceived as
                                                             c                  d
        beeing longer
                                         Standard distance
                                         Estimate
                                         Non-veridicality
Rock and Kaufman
                                               standing              lying




                                 eyes
   Tošković (2007)
       For near distances,
        such as 1m, visual
        space is isotropic
       For larger distances
        (3m and larger) visual   head
        space is anisotropic
   For distance estimates,
    visual system uses
    additional information
    from:                        body
       Vestibular system
       Neck muscles
                                    physical      perceived   deviation      perceived-
                                    distance      distance                   physical size
TO RESUME:
   In a reduced cue-situation:
       For perceived distance, visual space is anisotropic
       It relies on additional vestibular and kinesthetic
        information
       Anisotropy – an internal model of visual space
   In a full-cue situation:
       ?
    AIM
   Does visual space anisotropy exist in full cue
    situation, as in reduced cue situation?
   Does kinesthetic information influence distance
    perception in full cue situation, as in reduced cue
    situation?
   Does visual system relie on its internal model of
    space even when visual information are present?
METHOD
   Two experiments were conducted, with participants
    lying on their left side of the body
       Head moving does not change vestibular information
       Uniform distribution of depth cues in all directions
   Sample: 37 psychology undergraduates and high
    school students
   Stimuli:
       three luminous objects
       rectangular in shape
       size: 7* 5 centimeters
EXPERIMENT 1: reduced-cue
   Sample: 13 psychology undergraduates
   Procedure:
       Participants estimated distances
           In a dark room – reduced cue situation
           Lying on a floor, on left side of the body
           With special glasses on their eyes (with horizontal apertures 1mm wide)
           With rectangular frame around their head
       Three standard distances to estimate - 1, 3 i 5 meters
       Three directions of estimate
           horizontal (00)
           middle – tilted for 450 regarding to horizon
           vertical (900)
       Task – equalize the distances of three stimuli on a three different
        directions
frame   glasses   stimuli
RESULTS
   DIRECTION: horizontal – middle
       NO significant effect of direction
       NO interaction between direction and distance
   DIRECTION: horizontal – vertical
       Significant effect of direction
       Significant interaction between direction and distance
   DIRECTION: middle – vertical
       Significant effect of direction
       Significant interaction between direction and distance
                      F(2, 24)=1.7337, p=.19803                                   F(2, 24)=8.3619, p=.00176                                    F(2, 24)=12.890, p=.00016
                7                                                         7                                                            7


                6                                                         6                                                            6


                5                                                         5                                                            5
average match




                                                                                                                       average match
                4                                         average match   4                                                            4


                3                                                         3                                                            3


                2                                                         2                                                            2


                1                                                         1                                                            1

                                                                            5m                                                          5m                                          5m
                0                                                         0 3m                                                         03m                                          3m
                    0 degrees                45 degrees                          0 degrees                90 degrees                         45 degrees                90 degrees
                                                                            1m                                                          1m                                          1m
                                DIRECTION                                                    DIRECTION                                                    DIRECTION
   Visual space is being
    ELONGATED towards vertical
    direction
       For the distances larger than 1m
       Effect is NOT measurable on 45o
        tilt from horizontal direction




       In a reduced-cue situation
        visual space is anisotropic:
           neck muscles information
            influence distance perception
EXPERIMENT 2: full-cue
   Sample: 24 high school students
   Procedure:
       Participants estimated distances
           On an open field – full cue situation
           Lying on a ground, on left side of the body
           With special glasses on their eyes (with horizontal apertures 1mm wide)
           With rectangular frame around their head
       Three standard distances to estimate - 1, 3 i 5 meters
       Three directions of estimate
           horizontal (00)
           middle – tilted for 450 regarding to horizon
           vertical (900)
       Task – equalize the distances of three stimuli on a three different
        directions
frame   glasses   stimuli
RESULTS
   DIRECTION: horizontal – middle
       No effect of direction
       No interaction between direction and distance
   DIRECTION: horizontal – vertical
       NO effect of direction
       No interaction between direction and distance
   DIRECTION: middle – vertical
       NO effect of direction
       No interaction between direction and distance
                      F(2, 46)=.23235, p=.79359                                  F(2, 46)=2.2548, p=.11637                                     F(2, 46)=.00378, p=.99623
                6.0                                                        6.0                                                        6.0

                5.5                                                        5.5                                                        5.5

                5.0                                                        5.0                                                        5.0

                4.5                                                        4.5                                                        4.5
average match




                                                           average match




                                                                                                                      average match
                4.0                                                        4.0                                                        4.0

                3.5                                                        3.5                                                        3.5

                3.0                                                        3.0                                                        3.0

                2.5                                                        2.5                                                        2.5

                2.0                                                        2.0                                                        2.0

                1.5                                                        1.5                                                        1.5

                1.0                                                        1.0                                                        1.0

                0.5                                                        0.5                                                        0.5
                                                                           5m                                                            5m                                         5m
                0.0                                                        0.0
                                                                           3m                                                         0.03m                                         3m
                      0 degrees               45 degrees                         0 degrees               90 degrees                           45 degrees               90 degrees
                                                                           1m                                                            1m                                         1m
                                  DIRECTION                                                  DIRECTION                                                     DIRECTION
   Visual space is NOT being
    ELONGATED towards vertical
    direction
       Perceived distance does not
        change with viewing direction




   In a full-cue situation visual
    space is isotropic:
        neck muscles information
         does NOT influence distance
         perception
CONCLUSIONS
   In a reduced-cue situation:
       For near distances, such as 1m, visual space is isotropic
       For larger distances (3m and larger) head tilt ELONGATES space
        towards vertical direction
       visual system uses additional kinesthetic information from neck
        muscles
   In a full-cue situation:
       For all distances visual space is isotropic
       Head tilt does not change visual space towards vertical direction
       visual system does NOT use additional kinesthetic information from
        neck muscles
   Presence of visual information reduces significance of
    kinesthetic (non-visual) information for distance perception

				
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