[visionlist] geometrically ambiguous images

[vaegan]

Dear Ben,
There are indeed a class of shapes that a more than triply ambiguous but
multiply ambiguous. 
If a white dot immediately behind a rotating white wire figure is steadily
fixated against a black background with full stereo vision it will,
initially, be accurately seen as rotating. The depth information and many
other stimulus features adapt and appear altered. This is consistent with
the general sensory phenomena of adaptation and after effects. The rotating
shape can then be seen in a multiplicity of configurations. There are many
patterns of movement (reversed, flat, flapping). additional lines and
colours and different combinations of these.
There is an inverse relation between the number of different forms seen and
the rate of alternation between forms within the set reported by any S. I
suspect this is a function of steadiness of fixation.
I have described this class of illusions in a very old paper.
Vaegan. Two parameters measure perceptual transformations during monotonous
stimulation. Quart. J. Exptl. Psychol., 1976, 28, 583-589.
Illusions and after effects are only two cases amongst many (dreams,
hallucinations) where we know there is no strict correspondence between our
sensory experience and 'reality'. This does not cause us to doubt the
reliability of our everyday experience because it occurs in predictable
restricted specific circumstances.

yrstrulyvaegan 

Preferred contact: - Mobile & Dir: +61  0404 468 100 or vaegan at unsw.edu.au
        
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