If Seeing is Believing, We Might Need to Lower Our Faith

 Our eyes process 36,000 bits of information per hour, taking around 65 percent of our brain's capacity, the most out of any organ, in order to deliver our reality to us. In the center, where your optic nerve resides in a small blind spot, the hole in our vision, which, unless you develop certain eye diseases, you would never discover. This blind spot is filled in by the brain through the processes of perceptual filling, using contours in the space, past experiences, and the surrounding colors and lighting to make up the difference for this small region. This skill, while incredibly important to providing us a full field of vision, leaves us vulnerable to visual tricks. 

See for yourself, hold these cards out arms length, focus on the dots, and take turns closing each eye. You will notice the stars disappear. 

Traditionally, there are two theories to explain the neurology behind perceptive filling: symbolic and isomorphic. Proposed in 1988 by Kingdom and Moulden, the symbolic model states that perceptual filling is not a neural filling process; rather, it's a system that ignores the blind spot and simply fills it with the “more of the same” of its surroundings. This theory implies that there is no retinotopic representation of the filled-in surface, meaning that we are completing an object rather than piecing together a surface that unites the surrounding areas of our blind spot. As further studies in the field were published, isomorphic theory rose to prominence, where there is substantial evidence that the neural signals and the activation of the retinographic map occur. Work by Fiorani(1992), Matsumoto and Komatsu(2005), and Redies (1986) built a body of work supporting this theory(1, 2). 

Preceptual filling goes beyond these blind spots but contributes to some optical illusions you may have encountered, and also supplements for lesions that may have damaged the eye after an illness or injury. Two more popular illusions you may have encountered are Craik O’Brain-Cornsweet Effect (COCE), in which two surfaces with the same luminance appear to differ due to their neighboring areas, and the water color effect(WCE), in which a pale or luminous hue seemingly fills an enclosed area because of its presence next to a dark contrasting line. Both effects are hypothesized to occur due to the surface edge model, which deals with the initial survey of the visual field and contextualising each surface and contour in reaction to its surroundings. It often can be overcome after a longer stable survey of the area.

    WCE                                                        COCE(4)

Within the theory of isomorphism, there is an exploration of the relationship between surface contour perception and experience. This is known as the Bayesian hypothesis, which takes in the sensory surrounding input and refers to prior exposure to similar environments in order to fill in gaps of the field of vision, implying a hierarchical visual processing structure (6). Through brain monitoring of both humans and monkeys assessing visual stimuli, researchers Devinck and Knolckshow that there is feedback between N3A to V1 and lateral modulation in LO parts of the processing system (7). While these are highly technical components of our neural systems, this finding proves that perception is an adaptive process that is constantly occurring when looking into a visual field. 

But why care? Our brains have adapted to look quickly and make judgments between blinks in order to keep us safe and active within the environment. Our ancestors needed to assess danger in the wild. Quick contrast and assumption allowed us to speed up the processing time. The trade-off seems to be falling for a few silly optical illusions, but I argue it goes deeper than that. Since we have had the introduction of short-form media on cell phones, the content we consume has grown vastly. Marketing Essentials Lab notes that it takes 3 seconds for someone to scroll between posts (5). Within these three seconds, whether we choose to stick around or scroll by, we are absorbing visual stimuli, and with a quick turnover, we are engaging in perceptive filling. Quick engagement leaves us vulnerable to images that are purely crafted or missing essential elements, often edited or produced with AI. Media companies can leverage our brains against us to fill in poorly crafted adverts and even misinformation. When walking down the street, perceptive filling is an advantage; it allows us to assess danger quickly, preventing us from getting hit by cars or walking too awkwardly close to the person in front, but online, we might need to start to take a bit longer on each image. Fight these quick fill-ins to truly assess the quality of content we engage with, and possibly identify how much is poorly constructed or AI-generated. 

1-Spillmann, Lothar, et al. “Perceptual filling-in from the edge of the Blind Spot.” Vision Research, vol. 46, no. 25, Nov. 2006, pp. 4252–4257, https://doi.org/10.1016/j.visres.2006.08.033. 

2-Weil, R. S., & Rees, G. (2011). A new taxonomy for perceptual filling-in. Brain Research Reviews, 67(1–2), 40–55. https://doi.org/10.1016/j.brainresrev.2010.10.004 

4-This optical illusion will make you question your sanity. HuffPost. (2013, December 9). https://www.huffpost.com/archive/ca/entry/this-optical-illusion-will-make-you-question-your-sanity_n_4415061 

5-Team, T. P. (2023, October 3). The three second social media rule. Marketing Essentials Lab. https://marketingessentialslab.com/%E2%80%A8the-three-second-social-media-rule/ 

6-Nguyen, R. T., & Peterson, M. S. (2024). Bayesian analysis on Missing Visual Information and Object Complexity on visual search for object orientation and object identity. Attention, Perception, & Psychophysics, 86(5), 1560–1573. https://doi.org/10.3758/s13414-024-02901-x 

7-Spillmann, L., Otte, T., Hamburger, K., & Magnussen, S. (2006). Perceptual filling-in from the edge of the Blind Spot. Vision Research, 46(25), 4252–4257. https://doi.org/10.1016/j.visres.2006.08.033