Tag Archives: visual system

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?