Interesting optical illusion
http://www.patmedia.net/marklevinson/cool/cool_illusion.html
Interesting!
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3 Comments:
It's funny that you posted this. I just saw this the other day. Then I come to your blog and you have a link to it, too.
That's really cool. Why does the mind work that way. I'm color blind and didn't think I would see the difference in color, yet alone see all the colors disappear except for the circulating green one.
Thanks to my lecturer in London Metropolitan University - Tom Walsh, we can all understand this phenomenon. Below is the explanation he provided:
The illusion arises from
(a) colour afterefects: when the red colour mechanism (technically the
+R -G chromatically opponent ganglion cell)suddenly ceases to be
stimulated (i.e. a sufdden offset), a signal arises in its opponent cell
(+G -R) and we have a sensation of "green". I have often noticed this
effect myself when waiting in a queue of traffic. If the red brake
lights of the car in front go off, I get a brief sensation of "green".
(b) the disappearance of the spots is an effect of a pseudo-stabilized
retinal image. You know that even when we steadily fixate something,
the eye is always making very small movements. Without these movements
and with every retinal receptor receiving constant, unchanging
stimulation, the visual system would rapidly habituate and we would be
functionally blind. Years ago a man named Ditchburn at the University
of Reading managed to devise a technique to nullify the effects of these
small eye movements. He attached a very small mirror to a contact
lens so that the participant only saw the world through the mirror.
naturally, because the mirror was attahed to the contact lens and the
contact lens was attached to the eyeball, every time that the eye made a
slight movement, the image on the retina moved with it, so that the
image was stabilized ( stationary) on the retina. Participants reported
that after about 10 seconds everything disappeared into a sort of grey
fog. Vision only returned if they blinked or moved the contact lens.
(it also made them feel sick!) Now in the illusion that you sent to me,
we obviously don't have a true stabilized image, since we are not
wearing the Ditchburn device. However, the edges of the spots are fuzzy
and blurred, so the even though our eyes may be making small movements,
the intensity of light falling on our retinal receptors from the spots
is changing very little and not enough to maintain vision. It is
effectively a stabilized image! Hence, with reasonably steady fixation,
the dots disappear.
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