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P3D Re: Hollow Face Illusion
- From: Bruce Springsteen <bsspringsteen@xxxxxxxxx>
- Subject: P3D Re: Hollow Face Illusion
- Date: Tue, 5 Oct 1999 14:00:02 -0600
I went back to the antique store last weekend to look at the inverted
Jesus again and study my perception of it. It happens that I *can* see it
as convex, but not in the comin' at you stereo sense, or I can see it as
concave (my first reaction) by changing my "object hypothesis" to expect,
and therefore notice the stereo cues. In other words, the illusion is
totally under my control. This conforms to my idea that stereo perception
is a highly mutable experience - that people show a wide degree of
sensitivity to (or awareness of?) stereo cues, and that practice and force
of will can become a big part of how acutely we see stereo. I have
mentioned here before that I'm become noticeably more attuned to parallax
variations -as well as deviations from ortho viewing conditions - than I
was five years ago, as a consequence of practice and deliberate attention.
Yellott, in the SciAm article posits two possible causes for the perceived
"depth inversion" in the hollow face illusion, in spite of stereo
(binocular) sensory input. He suggests that either the mind ignores the
input from one eye, or that it reverses its interpretation of where left
and right retinal images are coming from. Then he show by experiment that
neither hypothesis works. I simply suggest that the brain can ignore or
"desensitize" itself to all stereo input in favor of its preconceptions.
It's not so strange to me that we can often *not* see something that is
objectively in front of us. We do it all the time. So the illusion seems
familiar phenomenon to me, and within my ability to control.
I bet some of you are skeptical!
Bruce
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