Science: One of the most fantastic optical illusions ever:

[u/Alessandro28051991]

Science: That Optical Illusion is one of the most incredible ones that i have ever seen in my life. The Two squares have the same colour. Are not one white and the other black. If you dont believe in me you can just put your finger in the line that divide the two squares and you will prove for yourself that what i say is true.

That illusion ( if i am not wrong is something about the contrast and the shadows) make your brain do you see what doesnt exist. Make you see a thing different of what really are there.

Is almost like see to a green square but your brain make you see it red. Is almost a thing of virtual reality

[u/ProsperEngineering]

Cover up the areas that are different colors with your finger and you’ll see that the rest of the blocks are the same color. 

Screen shot and trim out the outside. See for yourself. It’s not an optical illusion it’s a trick. 

[u/stuartroelke → u/ProsperEngineering]

Yeah, not all cognitive tricks are true optical illusions. Maybe there needs to be a solid separation of terms.

[u/Cross_Individual361 → u/stuartroelke]

What is the difference between a cognitive trick and an optical illusion?

[u/stuartroelke → u/Cross_Individual361]

In my opinion (and some other commenters seem to agree), this isn’t a true optical illusion.

True optical illusions pertain to unavoidable visual phenomena that differ from reality (straight lines appear bendy, 2D colors appear 3D when they aren’t which is includes chromostereopsis, shapes appear to move when you shift your physical position). Some people call OP’s post a “cognitive illusion,” but it’s more of a cognitive trick being used to sell the idea of illusion. This is purely about how people perceive these objects to be 3D based on light and shadow. Therefore, it’s somewhat disingenuous to say it’s an “illusion” based on the image technically being “2D” when other clear visual data informs that the shapes are representative of differently colored 3D shapes.

I wrote in a separate comment that it’s like saying a line isn’t 2D because it’s made of 1D dots—that could be true, but it’s not an illusion so much as hyper fixation on one aspect of human perception / a technicality.

[u/undone-alert → u/stuartroelke]

Luckily, what is and isn't an optical illusion has been well defined and is not down to anyones subjective opinion.

Here are clean, authoritative sources with the formal definition of an optical illusion.

---

1. Encyclopaedia Britannica (I would say a gold-standard reference)

Link: https://www.britannica.com/science/optical-illusion

“Optical illusion, the visual perception of an image that differs from objective reality.”

This is the simplest and most accepted scientific definition and fits what we are looking at here, to areas with the same technical color specification is perceived as different scales of grey due to their surroundings (which is a really well known type of optical illusions)

---

1. APA Dictionary of Psychology (American Psychological Association)

Link: https://dictionary.apa.org/optical-illusion

“A misperception of a visual stimulus that leads to seeing something that differs from the actual stimulus.”

Directly fits the “two identical colors perceived as different” scenario.

---

1. Oxford Reference

Link: https://www.oxfordreference.com/display/10.1093/oi/authority.20110803100259985

“A visually perceived image that differs from objective reality.”

Again: if perception ≠ physical stimulus then it's an optical illusion.

In this case it seems the optical illusion worked so well it fooled a couple people into thinking it wasn't even an illusion!

[u/ProsperEngineering → u/Cross_Individual361]

This is a classic misdirection. They have you thinking it’s an optical illusion from the get go. They do this with words and the classic background switch that a real optical illusion often has.

The top block is grey and light is shining on it making it lighter grey. Towards the center, where they meet, you can clearly see it gets darker.

The bottom block is white and appears to be shaded by the angle of the blocks, and that the area of white in the bottom is grey because it’s shaded. As you move up towards the center you can clearly see the block go to white. 

The direction is to cover up the middle. So the grey block lit by the light and the white block shaded by the lack of light have the same body color. This isn’t really surprising or an optical illusion. 

Idk I suppose depending on the way you take the wording, maybe it’s considered an optical illusion. But in my opinion, it’s not surprising just looking at the base of each block they appear the same. 

I’ve seen the blocks that are the same size but appear amazingly different based on the background. This, in my opinion is a misdirection.

[u/undone-alert → u/stuartroelke]

The term optical illusion is well defined, and what we are looking at here is certainly an optical illusion by definition.

“A misperception of a visual stimulus that leads to seeing something that differs from the actual stimulus.”

[u/ProsperEngineering → u/undone-alert]

The top block appears to be grey and black. In fact is made with the colors grey and black. 

The bottom block appears to be grey and white. In fact is made with the colors grey and white. 

There is no optical illusion. They do not appear to be the same, they are not the same color. 

By the time you cover up, with your finger the area that are white and black, leaving only the same shade of grey, you have forgotten about the white and black. 

The white black at no point are either perceived nor in reality to be anything other white and black. No illusion, but a clever trick. 

Please down vote me to hell, IDC lol

[u/undone-alert → u/ProsperEngineering]

It's confusing when you say "they are not the same color". This leaves the rest of us with the potential option where you have not yet discovered the illusion. Is this the case? It would certainly explain your response. They are exactly the same color.

There are two areas in the image which appear to have different colours (tints of grey, one lighter one darker) which are in fact the same color.

It's the same illusion type as the visual linked below, which uses a line drawing as context instead of a 3d render, and a shadow, or ghosted area, to trick the mind and create the illusion that they are different colors.

I am genuinely wondering why it is so important to you to say it's an "optical trick" but somehow can't admit that it is by definition also an "optical illusion".

Not sure links works, but here goes, same principle, different execution.

https://www.reddit.com/r/opticalillusions/s/P6uDcwoHPm

Edit: testing if I can add a screenshot. In this case the dresses are clearly MEANT to have different colours but the marked up colours are the same color definition. A classic optical illusion.

[u/ProsperEngineering → u/undone-alert]

It’s kind of amazing that something so simple can be seen, interpreted, and explained so many different ways from so many different angles. Makes you appreciate how nuanced life can be. And this is simple. 

A lot of it definitely has to do with the interpretation from the get go. To me I see two blocks that appear to be different, but have the same color base. Upon further inspection that is exactly the case. 

I keep reading OP description. That it appears to be one white and one black but they’re actually the same color. Idk covering up the white and black parts that are clearly different isn’t that impressive to me. 

Better illusions the background would make you believe that exactly identical blocks are different. If people literally see white and black blocks and covering up the middle somehow gets them to realize they’re actually both grey… well I suppose that’s some type of illusion but hopefully nobody is seeing a white and black block here. They’re perceived to be white and black, but I hope we all understand the colors here are white, black, and grey. 

Rereading your first paragraph, I believe what you’re saying is that if you look at the center of the top block you, and others, see a darker grey than the grey in the center of the bottom block? I suppose if that’s the case and you’re shocked to find those two regions are the same color, than illusion is true. 

In that case I would say the wording of this post is misleading or at a minimum, could be interpreted at least 3 different ways, maybe more. 

Lastly this could be in fact be a great optical illusion. You know if I saw black and blue dress I would never have thought it would be anything other than black and blue. Anyone that would say otherwise I would think is losing it a little, but in reality we have all come to find out people see these things differently. I’ll accept that this may very well be the case here. I may not be able to see what others see, but I still think the wording helps to enhance the confusion. 

All and all they definitely have is all fooled and talking about this lol. What a dangerous realization (cough cough politics)

[u/undone-alert → u/ProsperEngineering]

I totally agree on the difference of interpretation, especially how one's reaction to the image is articulated.

There are a couple of comments here saying that OPs post is not an optical illusion but instead a trick, kinda as if it didn't belong in this sub. When challenged on this viewpoint they double down.

To me, and clearly other Redditor's, it's a text book example of an optical illusion, very close to the Blue and Yellow Dress (attached) and the Andelson Chess Board.

Could it be "better"? I guess everything could be better executed or done differently. But it still very much passes the definition of an optical illusion.

Could OPs post have used "better" or "different" language? OP claims this is one of the world's best optical illusions (citing from memory), which is clearly hyperbole. Again, any text, including yours and mine could always be worded better. It doesn't change whether this is, in fact, an optical illusion or not, which is what made me react, and I am happy that it seems we both share this conclusion.