Understanding Illusions

Are these images different?


Optical illusions have always fascinated me. The way our eyes and brain work together and often trick us into seeing things that aren’t really there or that are different than they really are is hard to understand, or is it?

In April of 2018 Buzzfeed employee, Crystal Ro, wrote an article about this image that she found on Reddit. She wanted to try and see if the rest of the world was experiencing the same headache-inducing confusion that she was when staring at this image. After using photoshop to copy the image at 50% opacity, she laid the right image directly on top of the left. This is when she realized that these images were in fact perfectly identical, pixel by pixel. With knowing this, why is it still so difficult to look at them as if they are the same image? Why does the image on the right look like it is taken at a different angle than the one on the left?


The article mentions that one Reddit user, All-Cal, says this illusion is, “because the two streets come together at the bottom of the pictures. Your brain tries to perceive this as one image with a fork in the road and therefore the street in the picture on the left must be at a different angle than the picture on the right.” So, is this Reddit user making a correct assumption?

According to an article from Science Daily about how our brains see the world, this illusion could be due to the interaction of the visual system, through parallel processing, with the brain. This article mostly discusses a study about our perception of motion; however, it also mentions key information about how the visual system works. For example, the key finding from this research explains parallel processing as, “[how] the brain’s two visual pathways interact with each other instead of being separate.” This means that we resolve the vagueness that we see by making inferences through the application of our visual system and our brain.

It also turns out that our brains like to interpret things in the simplest ways possible. Sometimes this simplicity leads to errors in our perceptions of visual stimuli. In an article about unconscious inference, this phenomenon is discussed to explain how the perception of our vision is often problematic or even incorrect. For instance, we look at this image and try to understand it in a simple way based on the spacial cues. The depth of this image, perceived by the distance of the van in the background, the lighting and shadows, and the angle of the street that seems to meet at a point in the bottom left corner, cause us to perceive the image as one street. These features of the image that indicate position are called binocular cues. Our eyes are seeing it correctly, but because we are trying to make inferences based on these binocular cues, we interpret it in a way that makes the most sense to us. Therefore, we perceive the image as a simple fork in the road, just as All-Cal said. In short, this illusion can be described as a misinterpretation of visual stimuli.

When I first saw this image, I was skeptical that it was the same picture. Even so, using research articles, I was able to further understand the way our brain interprets the things that we see. I find it very interesting that we can look at an image like this and our eyes take in the correct view of it, but our brains change it slightly based on unconscious inferences and binocular cues. Just as the Reddit user All-Cal pointed out, we see roads that come together at a point almost daily, so using the shadow and movement of the picture, we interpret a simple fork in the road even when that isn’t the case. This makes me wonder, how much can we really rely on our brain when it comes to inferring our visual intake?

10 thoughts on “Understanding Illusions

  1. mocooper

    When I first looked at the pictures I started from the top and then worked my way down so it looked like the same picture to me all the way until the streets converge at the bottom of the pictures. It’s weird to look at but also interesting that our brain just kinda fills in that gap for us, even if it’s an unnecessary gap to fill.

  2. tanjina

    This is very very interesting to me and that is a very good question, how much can we rely on our brain? When I first looked at the images they looked like they were taken from different angles. It is so strange how the brain can change or fill things in for us without any conscious thought behind it. I was especially surprised that because of the way the pictures were put it made it seem like a fork in the road to our brains. That really explains how things are simplified by the brain to make things make sense. It is probably helpful to simplify things down for some situations but it really does make me wonder how often this occurs and how often it goes unnoticed.

  3. afinegan

    I found this to be an extremely interesting article because when I first looked at the pictures it was more of a broad overview without looking at in detail and I was first confused because I believed the pictures were the exact same and was confused that some people did not think that. But once I began to read the article I chose to look more in detail at the picture and noticed how the angles look different when you are focused on different areas of the pictures. Now every time I look at the picture I now see that they appear to be at different angles. This is a good example of top down processing which we learned this year because now that my brain has been trained to see a certain thing, it cannot revert to the original. This really confirmed the notion made in the article that you eyes can properly see an image but you brain can then mix things up and convince you that you are seeing something different. I find illusions to be a very interesting subject and the processes through which we process them to be very intriguing. It was interesting to learn about binocular cues which cause the confusion of the translation between what our eyes were taking in and what our brain was processing.

  4. blogmatt21

    I definitely find this interesting and this post clears some confusion about illusions for me. I am also fascinated that the brain prefers to operate in a manner that is simplistic. I wonder if maybe this if illusions are not only errors but maybe a way for the brain to compensate for the complexity of stimulus since it is geared towards keeping interpretation more simple. Thanks for posting about this subject matter.
    -Matthew Crawford

  5. sarahkrzywicki

    At first when looking at the pictures, I could not find what the difference was, once I started reading more of the post I saw it said something about the road so I then looked at the road and I saw exactly what the author was talking about. The visual fork in the road idea makes a lot of sense as to why we would interpret that, but I just find it crazy that we can see something one way, but then when it comes time for our brain to analyze the stimulus, it can change it.

  6. mhook

    When I first saw the two pictures, I saw them as the same and didn’t understand why people were viewing them as different. Then as I continued to analyze the photos, I started to second guess myself and see them as different, even though I was viewing them more closely. This kind of reminds me of the whole “Yanny vs. Laurel” phenomenon and how many people would hear it only as “Laurel” but then heard it as “Yanny” and couldn’t go back to hearing it as “Laurel”.

  7. krb8

    I think the last question you pose it a very eye opening one and one that people probably think about all the time since these kinds of pictures and things do confuse us so much, it seems so complicated to understand and I still don’t get it. Because even with the proof there, it is still so hard to see these two images as the same no matter how hard you try but, we get proven wrong all the time with these, so it does seem very hard to trust anything about our visual when it deceives us so much in this way.

  8. kourt21

    I find illusions to be very interesting because I feel like I am constantly being tricked by my brain. Although illusions can be headache inducing, I believe this one not to be the most engaging illusion. Of course, I was still duped by these images and the illusion created by them. I can tell that the images are the same, but my brain keeps trying to convince me that they are different. Illusions are very compelling to study but like most people, I was not overly curious about what caused our brains to trick us. It’s intriguing that our eyes see the images correctly but our mind is trying to interpret it in a way that was simple and made the most sense to us. Even with the knowledge that we are perceiving it completely wrong, we cannot unsee (while sometimes we can) the illusion our minds created.
    – kchiles

  9. alee9

    Illusions are usually based on manipulating the brain with an edited image that takes advantage of some natural process the mind uses to interpret its environment. I remember that some of the optical illusions from the chapter used perspective tricks with gradients or positioning to make us perceive false depth, but I haven’t seen anything like this before where a picture side-by-side with a copy of itself re-contextualizes the direction the road itself seems to be pointing. With the understanding that most optical illusions work precisely because they couldn’t be replicated in ‘real life’, it’s still fascinating that the brain can make an image more complex than it actually is in the process of simplifying it.

  10. lhannah

    Optical illusions have always intrigued me as well. It’s hard to understand how our eyes and brains deceive us when it seems that something is so straightforward and obvious. The way that things are laid out for us visually impacts how we experience them and when they are not what they seem, it is hard for us to understand how it works. The gif you included of the Photoshop screen comparing the two identical pictures really helped me put this concept into perspective. There is no way I’d be able to believe or see that the two pictures side by side were identical without the Photoshop visual. The part where you mentioned our “unconscious inferences” is particularly interesting because it makes me think about how many things I think I interpret correctly when in fact my interpretation is way off. This also makes me wonder if this illusion only applies to pictures or if it applies to real life visual stimuli. If so, I will look at the world and things around me in a completely different way! I appreciate how you linked the articles that you talked about directly in your post. That helped me to have nice easy access to the concepts you were discussing. Overall, I really enjoyed reading this post and I think you described the concept in a very understandable, informational way.

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