Here is another visual / brain image-processing test that I was completely skeptical about until I tried it, and was quite shocked in fact to observe it. It involves standing directly in front of a wall mounted mirror, say at distance of 18" from it, in a room that has very, very, low light—light that *just* suffices for you to see your face, and only when your eyes are fully dilated. To do this right, it's essential that you initially be able to see absolutely nothing of your face because it's too dark. The hardest thing about trying this experiment is that it requires light so low that it requires a wait as least as long as 10-15 minutes for your eyes to dilate enough so that you're able to see your face in the mirror. But be patient and try it. What happens at the time when your bored brain can just barely begin to see your face is that your face will present itself to you as a variety of incredibly grotesque images. And this period goes on for as long as several minutes. The first time I tried it I was shocked and immediately went for the light switch. This one definitely *is* like returning the great substance eras (eg the 1960s). But it is much cheaper and safer. On Fri, May 26, 2017 at 3:29 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Maybe I should mention that the effect seemed either very diminished or absent entirely when I kept my head still and just shifted my gaze around the aforementioned circle.
—Dan
On May 26, 2017, at 12:37 PM, Allan Wechsler <acwacw@gmail.com> wrote:
I can see what Dan is talking about. That image is complicated, though. It's very hard to say what aspect is eliciting the effect. For me the effect is pronounced at first, and then diminishes. It would be good to come up with more abstract images that also elicit the effect.
On Fri, May 26, 2017 at 3:19 PM, Adam P. Goucher <apgoucher@gmx.com> wrote:
Can reproduce Dan's illusion; unfortunately, cannot remember the sixties ... APG
Sent: Friday, May 26, 2017 at 5:21 PM From: "Fred Lunnon" <fred.lunnon@gmail.com> To: math-fun <math-fun@mailman.xmission.com> Subject: Re: [math-fun] Koosh illusion
Couldn't reproduce Dan's illusion. But I _can_ remember the sixties ... WFL
On 5/26/17, Dan Asimov <dasimov@earthlink.net> wrote:
I was looking at this photo of a Koosh ball:
https://en.wikipedia.org/wiki/Koosh_ball#/media/File:KOOSH.png <https://en.wikipedia.org/wiki/Koosh_ball#/media/File:KOOSH.png>
from about a foot away from my 27" computer screen.
Closing one eye, I moved my head in a very small circle while remaining a foot away: just a little to the right, then above, then to the left, then below (rinse, lather, repeat) of dead center on the Koosh ball — and while doing so, have my gaze cycle around a circle on the screen centered at the center of the ball's image. (The screen circle is roughly the nearest screen point to my head at a given moment.)
The result: a persuasive illusion that the image is changing slightly due to parallax, that is, depending on the varying positions of the eye as it moves in a circle.
Question: Is this a known illusion? Does it generalize beyond Koosh balls?
—Dan _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
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-- Thane Plambeck tplambeck@gmail.com http://counterwave.com/