Crossing the Line: How our Brain Keeps Vision Seamless and Why Symmetry is Key.

 Most of us have never thought about the center line of our vision or actively seek it out. You look to your left, you look to your right, and even so the world manages to keep is balance and stay in one piece. In a recent article by MIT News, “How the brain splits up vision without you even noticing”, tells us why. As something moves across your view, the brain quietly passes the information from one hemisphere to the other so there isn’t a noticeable glitch or gap. For example, if runners are running a relay race and one passes the baton to the next runner up, and they match their speed so the baton is handed off cleanly and the race will continue without a hitch. This speaks to how perception works in everyday life, such as walking down a crowded sidewalk, during a sporting event, or even while doom scrolling through reels. 

In our Neuroscience seminar, our reading “The role of vertical mirror symmetry in visual shape detection” by Machilsen et al. (2009) talk about how the left and right side of our vision matching isn’t a design for aesthetic purposes but rather helps our brain find shapes in clutter. In the experiment from the reading, participants were asked to spot outline of shapes made from tiny line fragments with slightly turned little lines that made the outline so the shape was harder to see. Through the multiple conditions, shapes that were symmetric were much easier for the participants to decipher compares to chapes that were symmetric. This shows that symmetry acts as shortcut for when scenes aren’t clear or messy for our brains to outright decipher, so our brains use the other half that is clear or more recognizable to fill in the other half. 

But how do these ideas work together? The article by MIT explains how features slide across our vertical midline and the two hemispheres of our brain work together to keep it a continuous scene. Since vertical symmetry is connected by the midline, our brains are able compute that this half should mirror the other half. Symmetry pops because our brain is designed to create one big picture even with many moving pieces. This also confirms what Dr. Baker, our guest speaker, mentioned in his talk. Our vision is built up of many little pieces that work together to create the big picture. 

References: 
https://www.luc.edu/psychology/people/facultyandstaffdirectory/profiles/bakernicholas.shtml

David Orenstein  |  The Picower Institute for Learning and Memory. (n.d.). How the brain splits up vision without you even noticing. MIT News | Massachusetts Institute of Technology. https://news.mit.edu/2025/how-brain-splits-vision-without-you-even-noticing-0926

Machilsen, B., Pauwels, M., & Wagemans, J. (2009). The role of vertical mirror symmetry in visual shape detection. Journal of Vision, 9(12):11, 1–11, http://journalofvision.org/9/12/11/, doi:10.1167/9.12.11.