Believe it or not, the brown square in the middle of the top face of the Rubik’s Cube and the orange square in the middle of the front face that is in shadow are in fact the exact same colour. Again, if you don’t believe me, cover up everything else in the image except for those two squares.

Even when you know the correct colours of the squares there is seemingly nothing you can do to see it the correct way when you look at the image in its full context.

Can you agree with yourself?

The next type of illusion I want to explore is one where it is possible to interpret it in multiple ways but never more than one way at a time. Take the famous “Brainstorm/Green Needle” audio illusion that became popular a few years back. Here is a link to it. Check it out for yourself and then come back here: https://www.youtube.com/watch?v=qXxV2C1ri2k&ab_channel=GuardianNews

Most people should be able to hear either “Brainstorm” or “Green Needle” and what you hear is entirely based on what you concentrate on prior to the sound playing. It is also very difficult or perhaps impossible to hear both phrases simultaneously. 

What does this mean?

Many people, including perhaps yourself, may claim to see the world objectively, or “you see the world as it is.” You might describe yourself as pragmatic, or rational. Before I eloquently burst your bubble, let’s come to some definition of what the “real” world really is. Defining it could be discussed at book-length, but for now I will say this:

The real world, for the purposes of this article, is the world in its raw physical form as described by the laws of physics. That is, a real image is the unique combination of photons that interact with said image. A real sound is the unique combination of air particles that vibrate in accordance to the vibrating object that stimulates them. This is to be taken as completely independent from human emotion, bias, interpretation and thought.

Every image our eyes take in is interpreted by our brains and (as far as I know) there is nothing we can do about that. It is therefore impossible for a human to see an object for how it truly is. To prove this, look no further than the illusions provided above.

Beau Lotto, who studies illusions like this and gave a TED Talk about them, describes how our visual perception evolved to interpret the world in a way that was useful in the past, not how it actually is. It turns out it isn’t useful for our survival to see the world how it actually is. To show this, take another look at the Rubik’s Cube illusion. Take note how your brain interprets colour it believes is in shadow compared to how it interprets colour it perceives to be directly illuminated. In reality, the colour reflecting off an object varies drastically compared to if it is in shadow vs in direct sunlight. 

Borrowing an example from neuroscientist Anil Seth, if you look at a blank white sheet of paper indoors it will look white to you. If you take the same sheet of paper outside under direct sunlight it will also look white to you. But if you took a picture of the paper in both situations and then held the photos next to each other you would see the papers as different colours. This concept is known as white-balancing and is something your brain does automatically. In fact, this is one solution for the dress debate that Seth describes. Different people have slightly different white-balancing mechanisms, and it is possible that the image of the dress — given its colours and background — has reached a perfect sweet spot for one group of people to white-balance the image more than the other group of people such that they actually see a completely different set of colours inside their brains.

Allow me to suggest a potential reason why white-balanacing in humans may have been useful in the past. If you are living as a hunter-gatherer in a band of 100 humans on the African savannah, it would be very important for your survival to be able to quickly recognize the members of your tribe and distinguish them against other humans from rival tribes. Imagine you are conversing with your compatriot Adim, under the shade of a tree. If you both move into the sunlight you will of course still see that the person you are conversing with is your friend Adim. In reality the appearance of the colour of his skin will have changed dramatically as you moved from the shade to the sun, so much so that if you saw colour exactly as it is, you might even begin to doubt that the person under the sunlight is not the same person you saw in the shade. Even if there was a 0.1% chance that you got alarmed at the change in appearance of Adim you might mistake him for a member of a rival tribe increasing your likelihood of lashing out at him. There is no situation where that would be useful for survival, so our evolution made it so your brain balances the light to view Adim as having the same skin colour regardless of his setting.

Another solution to the dress

Here is one study that attempted to explain the dress phenomenon: https://jov.arvojournals.org/article.aspx?articleid=2617976

One of the arguments made in this study was that your chronotype (the time you prefer to go to bed) has an influence on what colours you see in the dress image. The study found that night owls — people who prefer to stay up late — are more likely to see the dress as black and blue. Vice versa, morning larks — people who prefer to sleep and wake up early — are more likely to see the dress as white and gold. This is not a perfect correlation, there is plenty of overlap, but it is an interesting explanation. 

The reason for this, suggested by the paper, is that people see the dress one way due to assumptions they are making about the lighting conditions in the image. Night owls tend to spend more of their time indoors under artificial lighting and so they’d assume that the dress is lit artificially (that is with light bulbs as opposed to the sun). Artificial light is quite orange/yellow in colour and so if you assume the dress is artificially lit your brain will filter out those colours to attempt to see the true colours of the dress, black and blue.

Alternatively, according to the paper, morning larks will assume the dress is lit by the sun. Sunlight has a lot of blue in it, so your brain will attempt to filter out the blue in the image to attempt to see the true colours of the dress, white and gold.

This is an interesting interpretation, and I’d encourage you to read the full study yourself. The correlations are not completely convincing but perhaps are one reason to explain such a fascinating phenomenon.

You only hear what you want to hear

Have you ever been in a room filled with people with multiple conversations happening simultaneously? Parties are good examples here. Heard from a distance, multiple conversations  can sound like gibberish, but if you are at the party it is possible to listen and focus on just one conversation. It is also possible to switch your focus to a completely different conversation. It is also nearly impossible to focus on and make sense of both conversations at the same time. Our brain seems to have a built-in mechanism for selective listening. This is a great tool for situations such as parties. If we didn’t possess this mechanism we might be faced with an overwhelming wall of noise, unable to understand what anyone is saying. The Brainstorm/Green Needle audio illusion is a more controlled version of this phenomenon. 

This proves that you can literally hear what you choose to hear. But can this concept be taken further? How many times have you been in conversation with someone only to zone out part way where you only hear a portion of the words they are saying? Or how about hearing all the words someone says but interpret it differently from them? This is a fascinating concept to explore altogether which I will touch on more of below. For now, the fact that two people can be presented with not just the same image but also the same sound, and come to completely different conclusions just further emphasises that you don’t see the world for “how it is.” You begin to realize that the world is constructed in your mind.

We evolved to interpret the world in a way that was useful in the past, not how it actually is

This fact is one of the most profound aspects of being human. It is an insight that is not obvious to most people; yet it is proven by the illusions shown above. Furthermore, it has numerous implications in many other areas of life. To me, the first obvious area is politics. It is no wonder we can’t agree on simple political notions when we live in a world where people can’t even agree on the colour of a dress. Even when presented with identical information people interpret the information in different ways. Just think about, for instance,  debates on climate change, abortion, universal health care, etc. People on all sides can choose to adopt and ignore certain pieces of information. It is no wonder we can’t seem to collectively come to agreements on these and other critical issues.

We all see the world slightly differently

Some of us see black and blue, some see white and gold. Going further, people have different tolerances for temperature, conflict, cognitive capacity, levels of empathy, physical strength, and past traumas. People live in different parts of the world, have different educations, have different spiritual beliefs, and countless more dimensions of distinction. This makes every human unique and, in turn, means that every human sees the world differently.

Semantics, linguistic meaning, is the first level you need if you are conversing with someone, and you want to understand each other. Let’s take a crude example. Here are a bunch of images of chairs or things resembling chairs: