ucbesvax.turner@ucbcad.UUCP (06/02/83)
#N:ucbesvax:1100001:000:2582
ucbesvax!turner Jun 2 03:16:00 1983
Talk of retinas, and composition of daemons for the "retina"
of a computer-resident intelligence, got me to thinking of my own retina.
I am not an expert in neuro-ocular phenomena, so if you are, please bear
with me. I am wondering if there are explanations for some of the
following perceptions:
1. One day some years ago I managed to walk on a railroad
rail for about 1/2 a mile. For at least fifteen minutes
afterward, there was a vertical band in my field of vision,
crossing the center, which seemed to be moving upward.
This band corresponded to the rail I had been staring at.
I was able to repeat this effect.
2. In a quiet, distraction-free, dimly lit environment, I am
able to look at an object against a uniform background,
and somehow make it blend in enough with its background
that it seems to disappear. This requires considerable
effort, and seldom lasts longer than a few seconds. Usually,
the object reappears when I try to focus on some feature
or detail that seems "behind" the object. I am fairly sure
that this is not simply a matter of coordinating both
eyes so that both blind-spots coincide over the image of
the object. It is definitely in the center of my vision.
The image also reappears if I move my eyes at all--and
since small eye movements are involuntary, this effect
suggests that these movements play a role in keeping
retinal responses flowing, whereas the image would
decay otherwise.
3. Recently, I have been playing a video game ("Quantum", Atari)
that has an interesting feature: there is an object which
moves around the screen (itself worth only 100 points)
that leaves behind images of itself that shrink down to
a point and disappear. Capturing (before disappearance)
these images is worth 300 points. When I play to make points
by capturing these shrinking images, there is a persistant
after- effect that is most apparent when trying to read: as
my eyes skip around a page, letters and words on it seem
to shrink. This does not happen when I play and ignore the
shrinking "particles", or capture them only incidentally.
The effect seems related to searching for and focussing on
these images for several minutes of play. It is often very
pronounced and distracting.
The human visual system seems to be educable at several levels.
Perhaps there are interactions between these levels that haven't
been explored yet.
Comments appreciated.
Michael Turner
ucbvax!ucbesvax.turner