You probably thought what a silly question that is in the header image. “That’s Coca-Cola, obviously!” But check again, read the letters on that can out loud, very carefully, one by one… Did you notice? It says Coca-Co, not Coca-Cola. One-fourth of the letters is missing. But chances are your brain literally saw Coca-Cola, including the two letters that are not on the can… That’s a very curious finding from MRI studies of the brain: our visual neurons can be activated even when some visual information isn’t present. I was amazed when I read that in ‘A Trick of the Mind – How the brain Invents Your Reality’, by Daniel Yon.
CONTENTS: Kanizsa’s triangle | Seeing what is really there | Why is this important?
Originally published: 20/06/2026 – Last update: 23/06/2026
If you are a regular reader of my blog, you may know I sometimes read books that seemingly have no relation to print. Thinking, Fast and Slow by Daniel Kahneman, which is an introduction to behavioral economics and the difference between System 1 and System 2, is one of them. And last year I read ‘Everything Is Predictable – How Bayes’ Remarkable Theorem Explains the World’ by Tom Chivers, which shows the basics behind ‘predictive processing’.
Kanizsa’s triangle
At this moment, I’m reading a book on neuroscience and psychology. The author is Daniel Yon, the director of The Uncertainty Lab. He researches how our brain works. Which is a fascinating topic… And it does relate to print quality. It relates to everything.
In the first chapter, he mentions a well-known experiment, Kanizsa’s triangle. Check out the image below. What do you see?
I guess you will say it shows three black circles, a black triangle, and a white triangle on top of them. Most – if not all – people see this. But look very closely, is that really what you see, what is shown on your screen? (and this is the part where your brain might start to crack, where thinking might start to be painful)
Did you notice? There is no white triangle in the image. That’s just something our mind sees. And those black circles? These aren’t full circles: these are missing a slice. Just as the black triangle is incomplete, there is only a collection of lines that are not always connected.
And this is the part where it gets very interesting: this image has been shown to people while they were in an MRI scanner. That’s the tunnel-like device that can make ‘sliced’ photographs of e.g. your brain, to show the activity in your gray matter. It can literally show which neurons in your brain are active. And guess what: that MRI scan showed that the visual neurons in the brains of the participants did ‘see’ lines delineating a white triangle… Even though these lines are not in the image.
And if I had taken an MRI scan of your head when you looked at the picture in the header, I could probably have seen that the visual neurons in your brain also saw those last two letters, the l and a. Your neurons probably did see Coca-Cola in full. Even though the can only says Coca-Co…
Here’s an excerpt from the book, on the test with Kanizsa’s triangle. (bold is mine)
“But if we record activity from these visual neurons in your brain, they don’t just reflect what the instrument is measuring, faithfully creating the patterns of light that are landing on the eye. The activity of these visual neurons is edited, adjusted, and reshaped – so that your brain sees what it thinks it sees, rather than the raw signals. If we look inside your visual cortex while you see configurations like the Kanizsa triangle, the neurons tuned along the edge of the imaginary shape still fire, even though there’s nothing in this region of visual space, nothing that these visual neurons could really be seeing. It’s as if the neurons know an edge should be there, even though it wasn’t in the measurements.
This kind of behaviour in single neurons tells us something quite profound. Because neurons like these can’t actually be ‘seeing’ anything in their input, their firing must be driven by knowledge of the world that is held somewhere else in the brain. Put another way, what results like these tell us is that your brain as a whole is generating hypotheses about what the world is like. These hypotheses get projected into the parts of the brain that are supposed to be doing the measuring. Rather than just taking a snapshot of the information landing at the senses, the ‘camera’ of your visual system is projecting its own interpretations back into the image that it’s recording – editing your visual perception so that it resembles your prior expectations.
Other studies show that this projection goes well beyond just adding a couple of imaginary edges. Your brain can edit a whole range of complex features into its own measurements, based on what it expects to be seeing.”
Wow.
The big question is, of course, why we see that triangle, why we see Coca-Cola (including the l and a) in the top image. Our brain, which uses an enormous amount of energy compared to the rest of our body, is using tricks to be more energy-efficient. So it does not require a high-resolution image, which is then evaluated in detail. It does something different…
From the book: “In follow-up experiments, it looks like what happens is that higher regions of the brain project predicted inputs back into these regions – a bit like a rough line drawing, sketching out a guess of what ought to be there. (…) These top-down projections are always running, even when your eyes really are being presented with an image. This means that what you perceive is always suffused with your hypotheses and shaped by your expectations.”
It’s because you know the brand is Coca-Cola that you see Coca-Cola. Your expectations – the full name, and also the iconic red – shaped the image in your brain: ‘predictive processing’.
BTW: that conclusion that our brain sees what it expects to see, also explains why about 1 out of 3 print professionals claimed to see a color difference between identical flat copies… They were asked if they noticed a color difference, so their brain showed one.
Seeing what is really there
It is very hard NOT to see the white triangle, just like it’s very hard to read ‘Coca-Co’ instead of Coca-Cola. It’s only when you consciously want a very detailed evaluation of the visual information – like when I asked you to check the name on that can in the top image, letter by letter – that your brain will be able to go beyond those hypotheses or mental images and evaluate more visual information. It’s only then that you notice that two letters are missing. You need to flip a switch in your brain: you need to activate ‘System 2’, the slow but accurate part of your brain, as I explained in this article.
And it’s just the same when looking at brand colors: it’s very hard not to identify a multitude of reds as Coca-Cola red. It’s very hard to see the shadows, gradients in cans, and shifted boxes in a real-life setting, as I showed in my previous article: your brain corrects for these influences. You really need to flip that switch and activate that supercritical but slow part of your brain. And that’s what happens in press checks, where you take a lot of time examining what you see. But not when shopping, then System 1 and predictive processing make the decisions…
Back to the image in the header. I took a few more pictures. And, e.g., in the next one, you can see that also in other types of cans, even when the full name is printed on the can, it isn’t fully visible… I admit: I hadn’t noticed that before… I had always read Coca-Cola in full…
But let’s put some more cans in the picture. And indeed, in most cases, the name Coca-Cola is not fully visible…
And also, the color is not exactly the same. These cans in the image above will NEVER have the same visual impression: the two on the left are printed with transparent ink, the two on the right with opaque ink. In the first two, the color will have a metallic look, the other two not. A very different visual impression, if you ask me.
Although it’s not as visible in the picture as in real life, the two cans on the right have a different color (when looking at it with the print part of my brain activated). The one on the right is more towards orange… But still, your brain will ‘see’ it as Coca-Cola red, unless you really force your brain to look more closely and challenge everything. What a brand owner and print buyer are doing during a press check (and let’s not forget: under perfect viewing conditions). But no consumer will ever do this. Even I have to (consciously) turn on the ‘critical color’ part of my brain. And when I don’t, embarrassing stuff happens…
Check out this little experiment that I did with my girlfriend. She only noticed a color difference between these two packages when I pointed it out… When I first asked what she saw, the answer was: two packages. When I asked if she saw a difference between the packages, she only mentioned that one of them was damaged. She only noticed the color difference in the background behind ‘Golden Syrup’ when I pointed it out to her. She was not trained to see these kinds of color differences, however, people in the printing industry, like you probably are, are accustomed to looking very closely at this kind of print and color, activating that System 2 that I already mentioned.
Back to Coca-Cola! From time to time, there are also these special Coca-Cola editions, like the two on the left in the image below. With again another shape. But nothing our mind wouldn’t accept as conforming to that mental image, that hypotheses what a Coca-Cola can should look like. If you are a Coca-Cola buyer, you would put these in your shopping basket.
In case you were going to argue that, yes there are indeed differences between different editions and batches, but you will never see two different ones out in the wild, check the image below, of a vending machine…
BTW: would the owner of that vending machine allow this kind of difference if it would actually hurt his income? Think about that.
In case you didn’t know: even though we can see millions of different colors, our color memory is very limited, as several studies have shown… E.g., our color memory tends to shift towards the center of a limited amount of color categories, as shown in this study. Even in an ‘undelayed’ setting, where at the center of a screen a square with the reference color was shown and participants had to pick the same color from a circle surrounding that square (with a neutral color between the square and the circle), there was already a shift towards the middle of that color category visible…
Why is this important?
Our brain works in wonderful ways. Viewing the world is nothing like taking a photograph: it’s more like a quick check if the world conforms to hypotheses in our mind, like what a can of Coca-Cola looks like. And while doing that, our brain literally sees things that aren’t there. Everybody sees three black circles, a black triangle, and a white triangle. But that’s not what the pixels on your screen are showing, where there is ink or toner on paper, in case you printed it out. And still, our visual neurons ‘see’ e.g. a full white triangle.
Also, when shopping, your brain might see things that are not there, based on the mental image of, e.g., that Coca-Cola can. Only a part of the name is visible? No problem! Your brain sees the full name. A darker color due to shadows? No problem! Your brain sees what it knows as the original color. A color gradient, due to the curvature of the surface of the can? No problem! Your brain sees the same color all around. (personal note: it is VERY hard to see the gradient, as if my brain doesn’t allow me to see it, but it definitely is there)
To be able to detect tiny color differences, you have to force your brain to take a very critical look at the light that touches your retina, you have to deliberately and consciously decide to evaluate every single pixel of that image on your retina. It’s not the default setting of our brains, it takes too much energy to do. You need to flip a switch in your brain and activate that energy-consuming part.
And with all of this in mind, check the pictures from my previous article. All those shadows, shifted boxes, different substrates, … our brain sees just ‘Coca-Cola’ cans and bottles. Only when you look consciously at that, you might notice. Or, first take a picture, then check it.
As usual, a very interesting article.
Thx Henk!