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Where reality ends and your brain begins : Optical Illusions

→ by Danieru
I just had to re-post this as it was so popular last time. Enjoy (again)...

As I've been ranting on about reality, perception and the human mind for the past few days I thought I'd give you a glimpse into how much of reality your brain completely makes up. Today, OPTICAL ILLUSIONS... Check below for full explanations...

"[Above] you see a circle of blue-violettish (=magenta) patches, one of which briefly disappears, circling around.

Let your gaze rest on the central fixation cross, but observe with your “inner eye” the patches just when they disappear. With good fixation, you should see a strong greenish colour whenever the violet patch has disappeared.

When you are fixating well, after a few cycles you will actually see a rotating green spot! If your gaze is really steady, the magenta patches will disappear, leaving only a rotating green spot!


The temporal presentation enhances the well-known afterimage in complementary colour.

Jeremy Hinton writes: "The illusion illustrates Troxler fading, complementary colours, negative after-effects, and is capable of showing colours outside the display gamut." "
It is clear to see from this illusion that an 'after image' of colour can seem as real to your brain as 'real colour'. It begs the question, where does the real end and the after image begin? It gets a whole lot more crazy though when you see exactly how much of the world your brain completely makes up, check the blind-spot illusions below for a shock...

"For this image, close your right eye. With your left eye, look at the red circle. Slowly move your head closer to the image. At a certain distance, the blue line will not look broken!! This is because your brain is "filling in" the missing information.

This next image allows you to see another way your brain fills in the blind spot. Again, close your right eye. With your left eye, look at the +. Slowly move your head closer to the image. The space in the middle of the vertical lines will disappear."

The lines in both these images were finished off by your brain at the point where your blind spot is on the retina. It's amazing enough to see blank space become solid lines before your eyes, but how about more complex patterns?

I read a while back a trick you can do with your TV set. Stick a dot of cardboard, like the dot above, on to the right hand side of your TV set. With a bit of messing around, closing your right eye try and figure out where on the TV screen your blind spot lies. Now, stick a grey, 2 cm square of cardboard onto that spot on the TV and flick the channel over to a static fuzz image (you know, the fuzziness you get between stations). Now repeat the illusion by covering your right eye. In a few moments you should see the grey square become filled in by the static fuzz on the TV screen! Your brain is filling in complex, impossibly random patterns without hassle.

Could it be that the entire real world is in our perceptual blind-spot? The brain, it seems, is the true purveyor of reality.

Enjoy your illusions, check out the last few days posts for my pre-amble to this post...

Thanks I-Hacked, Michael Bach and Washington Ed-Faculty!
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Blogger D-Thinker said...

This is really fascinating, I know a written version of such a thing, which is very simple. That I try on people when I get bored.

June 07, 2005 4:45 PM    

Blogger Q said...

Found your blog at Blogexplosion.

That's some interesting optical illusions that I haven't seen before. Good post!

June 07, 2005 6:30 PM    

Blogger Jen said...

Ooh, fun!

June 08, 2005 1:47 AM    

Anonymous Anonymous said...

wow!!!! :O)))) the magenta totally disappeared at one point and all I saw was green

June 11, 2005 12:23 PM    

Blogger Dan tdaxp said...

Cool. Astoundingly cool.

I looked at the first one without seeing an explanation, and I actually listed the green circle as something that was "really there," when I tried to figure out what the illusion was.


-Dan tdaxp

June 18, 2005 2:15 AM    

Blogger Chyrene Pendleton said...

Interesting post - I love optical illusions.

June 21, 2005 12:56 AM    

Blogger Danieru said...

if you want some more amazing illusions then check out the 'Michael Bach' link at the bottom of the post... I love being in the knowledge that I have chosen to fool my own brain. It shows how consciousness and perception are not necessarily the same thing. Groovy stuff, enjoy

June 21, 2005 2:03 AM    

Anonymous Anonymous said...

cool, but only the first one works for me.

May 19, 2008 6:56 AM    

Blogger Kopachris said...

The blind spot thing worked similarly when I had an object on the carpet of my floor. When the object was in my blind spot, my brain filled in the carpet as if the object really wasn't there.

August 25, 2009 12:24 AM    

Blogger Faith said...

for some reason the blue line worked, but not the image below it. interesting demo of that. i knew the brain did that, but never had a clear demonstration like that. swell.

January 20, 2010 4:58 PM    

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