I remember not really "getting" these illusions when I was a kid. I just didn't find them interesting, it looked too straightforward.

The idea of a "2D screen inside our head" is not our natural intuition. Before learning about these things, I just felt that I simply percieve the environment around me. I don't see a flat pixel grid in front of me when I walk around, I rather have a model of the environment that I continuously update and I percieve the objects "from where they are", just like I feel leg pain as if it were "in my leg", despite the fact that pain actually happens in the brain. I see objects where they are in the 3D model, not where they are on a virtual screen.

The screen and pixels analogy may be so prevalent in modern times because of the TV, photos or even earlier realistic paintings. But early art was not really realistic, which I think either shows they were

  • not skilled enough to draw realistic art with perspective distortions and shading, or
  • they didn't think of vision the way we do today, they were more focusing on the objects and their prototypical shapes, rather than their position in the visual field and the "actual colors".

The second explanation seems more plausible to me.

These illusions are only illusions if you take the "2D screen and pixels" view of vision. Now that view is also important for technological applications, and it's also biologically relevant (retina cells are sort-of pixels), I'm just saying it's not really an illusion against builtin intuition.

I don't see a flat pixel grid when I walk around, either; I see a 3D scene (generally only where I'm currently looking; I mean, I can recall where things are when I'm not looking at them, but they're not in my current visual model, that memory has to be stored elsewhere).

And yet, a lot of optical illusions work for me; because (as in the case of the illusion in this article) the drawing is close enough to what the reality looks like to fool my "scene reconstruction" module in my brain, and I reconstuct the relevant 3D scene when I look at it. Som... (read more)

Bizarre Illusions

by MrHen 1 min read27th Jan 2010310 comments


grey square illusion
Illusions are cool. They make me think something is happening when it isn't. When offered the classic illusion pictured to the right, I wonder at the color of A and B. How weird, bizarre, and incredible.

Today I looked at the above illusion and thought, "Why do I keep thinking A and B are different colors? Obviously, something is wrong with how I am thinking about colors." I am being stupid when my I look at this illusion and I interpret the data in such a way to determine distinct colors. My expectations of reality and the information being transmitted and received are not lining up. If they were, the illusion wouldn't be an illusion.

The number 2 is prime; the number 6 is not. What about the number 1? Prime is defined as a natural number with exactly two divisors. 1 is an illusionary prime if you use a poor definition such as, "Prime is a number that is only divisible by itself and 1." Building on these bad assumptions could result in all sorts of weird results much like dividing by 0 can make it look like 2 = 1. What a tricky illusion!

An optical illusion is only bizarre if you are making a bad assumption about how your visual system is supposed to be working. It is a flaw in the Map, not the Territory. I should stop thinking that the visual system is reporting RGB style colors. It isn't. And, now that I know this, I am suddenly curious about what it is reporting. I have dropped a bad belief and am looking for a replacement. In this case, my visual system is distinguishing between something else entirely. Now that I have the right answer, this optical illusion should become as uninteresting as questioning whether 1 is prime. It should stop being weird, bizarre, and incredible. It merely highlights an obvious reality.

Addendum: This post was edited to fix a few problems and errors. If you are at all interested in more details behind the illusion presented here, there are a handful of excellent comments below.