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  • Writer's pictureMac Ling

Illusions & Diversity

Updated: Dec 12, 2021

Can understanding the brain's visual processes teach us to accommodate a diversity of human perspectives?

“Illusion is an anodyne, bred by the gap between wish and reality."

― Herman Wouk


Visions of reality

In a famous study, climbers with heavier backpacks estimated a hill to be steeper than those without backpacks did—specifically, steeper by 5 degrees (Bhalla & Proffitt, 1999). In the same vein, studies have shown phenomena such as swimmers in flippers judging underwater targets to be closer than do barefoot swimmers (Witt, Schuck, & Taylor, 2011) and parkour practitioners estimating a wall’s height to be lower than non-practitioners do (Taylor, Witt, & Sugovic, 2011). According to the scientists who conducted these studies (studies that also have their detractors), the reasoning for this phenomenon relates to how the brain processes visual information. Without getting into too many of the neurological specifics underlying visual perception, we can characterize this as the brain “interpreting” the sensory input it receives. What the brain perceives as reality, according to such theories, is informed by experience. Rather than conveying to you what is accurate, these studies suggest, the brain has evolved to give you information that is useful (Your backpack is heavy? Your eyes are warning you not to climb that hill!). As Pascal Willisch, professor of Psychology and Data Science at New York University, writes, “Vision is a cognitive act by which an organism tries to gain information about its environment in order to improve action.” This cognitive act is far from simple. Henry Taylor writes in “Sometimes, paying attention means we see the world less clearly”: “In reality, the conscious view I have of the world is the end result of an immense level of computation. My eyes register information about light, and that information is processed in several different systems located throughout my brain, before showing up in my visual consciousness. The impression I get of the outside world (the grass, the café, the hospital) is a very distant descendent of the information that first entered my eyes.”

Given this gulf between external stimuli and individual perception, how do we all come to an agreed-upon reality-and, perhaps more importantly, when don’t we? Many scientists suggest that since we each have different sensory experiences (what our senses have been exposed to in the past), our brains “interpret” sensory input differently. Some scientists describe this as a sort of “auto-correct”—the brain takes into account what it has seen before and combines this with the new sensory input to create an impression. As with auto-corrected text, sometimes the result is exactly what you meant, and sometimes it isn’t (with hilarious to disastrous results!). Perhaps this can help us learn something about compromise; about giving another person the benefit of the doubt and breathing in their air, in their experience, for a moment. What someone “sees” perhaps tells us as much about reality as it does about their experiences—and what a useful tool this is! What we call “reality” may be a multi-faceted thing, but taking into account a diversity of perspectives, we can certainly agree to take actions together. The world upon which we act, after all, is shared. Visual illusions, which we will look at later in the newsletter, bring this issue to the forefront in a fun way. Using these, we can understand the idea of experiential bias not only intellectually, but also viscerally (metaphorically speaking). Try some of the many illusions in the compendium here.


YOUR TASK FOR THIS MONTH (...should you choose to accept it)

"Neuroscience, then, can help explain stubborn polarization in our culture and politics, and why we’re so prone to motivated reasoning... If the science tells us our brains are making up a “story” about reality, shouldn’t we be curious about, and even seek out the answers to, how that reality might be wrong? ... It’s not about doubting everything that comes through our senses. It’s about looking for our blind spots, with the goal of becoming better thinkers. It can also help with empathy. When other people misperceive reality, we may not agree with their interpretation, but we can understand where it comes from."

Take a look at the illusions and explanations in Resnick's article, and then try the exercises below!


The word "bias" is incredibly (and understandably) loaded, but we should not make the mistake of thinking of bias as entirely negative. Once we do that, we are liable to discount it entirely, distancing ourselves from this "unseemly" phenomenon... rather, what is important is to be aware that we are all biased in our own ways and to become aware of our own biases and of other people's so that we can account for them in our views and decisions. In his book The Geography of Thought: How Asians and Westerners Think Differently... And Why, Richard E. Nisbett proposes a quick experiment to check cultural biases in visual interpretation. You can try the test on yourself below: STEP 1: Click to take a look at this image. STEP 2: Write down a description of this image (your "story" of the image, in a way). STEP 3: Check here for Nisbett's explanation of how participants in his own study responded. Nisbett identifies differences in how East Asians and Americans tend to respond to these questions, and he offers explanations as to why this may be the case and how such differences manifest in business and personal situations. STEP 4: Whether you agree or disagree with Nisbett's claims, whether you are East Asian or American or both or neither, try to absorb the different perspectives (including your own!) created through this shared visual stimulus of the image. Reflect on what Nisbett's conclusions might say about the way you tend to approach situations. STEP 5: The next time you are in a real-life situation (a business meeting, a discussion with your family, in front of a podium), consider how you can incorporate the likely mix of perspectives of the group in a constructive way. Sometimes, we can be so focused on working out our own perspective that we forget to take an equal amount of time considering how what we don't see might be equally "true." Without an identical brain, identical cultures, and identical experiences, it is highly unlikely everyone is seeing the situation identically. ONE STEP FURTHER: Depending on what category of thinking/perception you fell into based on Nesbitt's image experiment above, decide to live your life for a day using the opposite line of thinking. When you encounter problems, ideas, conversations, you will of course instinctively process it in your own way automatically. After that, however, do a conscious re-processing of it in the opposite way (as outlined by Nesbitt's categories). To remind yourself to do this throughout the day, you might need a logistical trick (you could wear a bracelet to remind you, set a timer on your phone to go off before pivotal moments of your day, etc). If you do try this, I'd love to hear about your experiences, so please do send me a note! How does it feel, and how did other people respond to you? How did the situation proceed differently than it otherwise might have?



Why does an apple still look red to us, even when placed in a shadow at night; why have we not agreed together that apples are the purplish color they sometimes appear? Why does the paint store offer such minute degrees of white, and how can a designer sometimes decide between 50 shades of white given that the amount of sunlight in a room—and thus the color of the paint—differs moment by moment as the sun rises and falls and a variety of hues of artificial lights come on? We all remember the internet sensation of the blue-and-black dress—or was it gold-and-white? (One explanation, put forth by Pascal Wallisch, suggests that chronotypes are the culprit: People who are night owls tend to filter in a way that causes them to see it as blue-and-black, while early risers are more likely to see it as gold-and-white.) Illusions have been classified and differentiated in several ways by scientists over the years. One classification separates these into four types: Richard Gregory proposed three specific classes of illusions relating to vision:

  • Physical (caused by the physical environment) – a change in light hitting the eye, as with a pencil bent in water.

  • Physiological (visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type) – if you move your eyes over a black and white grid, the colors may seem to blend together. Or shake your head as you look at this image—does an animal appear?

  • Cognitive (unconscious inferences) – the type discussed above in this newsletter, referring to experiences that inform our perception

The interesting thing about illusions is that it seems that they can be overcome—that is, you can believe something even if you don’t initially see it, and sometimes this information causes you to look further into the image until you are actually be able to see it. In some of the illusions below, what is interesting is the way that your eyes are able to understand or even see something differently when they are adjusted with the knowledge of the explanation. For instance, two lines may look different lengths or two colors may look vastly different due to the context, when they are in fact identical; sometimes, once the illusion is explained, we are able to believe something we could never initially have thought reasonable. The Ebbinghaus Illusion This illusion, which gained prominence in 1901 by British psychology Edward B. Titchener, was originally discovered by German psychologist Hermann Ebbinghaus.

Public domain image, via Wikimedia Commons

This is a classic size illusion. If you zoom in, you’ll notice that the orange circles are exactly the same size. Roughly speaking, due to a size comparison with the surrounding circles, we perceive the orange circle on the left as smaller than the one on the right because it is important to us that it is smaller than the circles immediately surrounding it. For a more detailed, scientific explanation, you can read the scientific paper.

The Gray Square Illusion

Edward H. Adelson, Copyrighted free use, via Wikimedia Commons

Given our expectations of the checkerboard and our experience with shadows, we expect Square A to be darker than Square B, right? If you look at these squares again without their context (you can even take a screenshot of a few pixels of each and compare them side-by-side), you’ll see that A and B are exactly the same shade. The credit for this illusion goes to Edward H. Adelson, a professor of vision science at MIT. The MIT website also provides a more detailed explanation for this illusion.

Oblique Anamorphosis

Hans Holbein the Younger, 1533 – public domain via Wikimedia Commons

Here, the idea of illusion enters artistic representation very literally. In Hans Holbein’s 1533 painting “The Ambassadors,” depicting Jean de Dinteville, French Ambassador to the court of Henry VIII of England, and Georges de Selve, Bishop of Lavaur, an image appears on the rug between that looks almost like an otherworldly flying saucer… viewed from a certain angle, however, can you see what the artist likely intended it to be? If you can manage to print this image and look at it from the side (or visit it in person in the National Gallery in London!) you will see that it is actually a human skull. What did Holbein mean by making this skull only apparent as such from a certain perspective? Read the art criticism on this in Holbein's Ambassadors-Making and Meaning, 1998, by the National Gallery.

*** Finally, it is worth noting that the relationship between visual illusions and our perceptions have been used to very concrete and sometimes life-changing psychological benefits. Mirror experiments with individuals with phantom limb syndrome, for instance, have helped to alleviate very physical symptoms of pain associated with the missing limb (the mirror reflects the existing limb, giving the impression there are two).

“Sometimes, paying attention means we see the world less clearly” by Henry Taylor [Psyche/Aeon] Taylor walks us through how the brain processes vision as well as some of the philosophical, metaphysical, and psychological ramifications of these facts. This article focuses on the idea of attention, disputing Descartes’s idea that one can learn more about something the longer one pays attention.


“Sometimes, paying attention means we see the world less clearly” by Henry Taylor [Psyche/Aeon] Taylor walks us through how the brain processes vision as well as some of the philosophical, metaphysical, and psychological ramifications of these facts. This article focuses on the idea of attention, disputing Descartes’s idea that one can learn more about something the longer one pays attention. “Visual Illusions and Optical Illusions Are Not the Same” by Pascal Wallisch [Psychology Today] With some light science, this article by Pascal Wallisch, author of The Life of the Mind, details the difference between visual and optical illusions.

This research journal article details the controversy that it terms the “paternalistic vision hypothesis,” outlining the argument supporting spatial subjectivity and then refuting many of its claims.

Some truly fascinating (and some animated) illusions!


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