By Veda Sanghi
In the image above, what do you see at first glance? A vase? Or two inward-looking faces? Whichever of the two figures you saw first, you’ll notice the other pretty quickly as well. This optical illusion, called Rubin’s vase, provides the brain with two interpretations that are easy to alternate between. However, just as many other optical illusions do, Rubin’s vase still requires extensive cognitive processing. Without having prior experiences, or in this case, knowledge about vases and faces, the brain would be unable to switch between the interpretations. With optical illusions like these, there is always more than meets the eye.
Optical illusions are defined as “the dissociation between the physical reality and the subjective perception of an object or event.” In certain images, the arrangement of colour, patterns, and light can deceive your brain into seeing things that are not as they truly appear. Our perceptions are shaped by the brain’s interpretation of what we see, but these observations may not always be interpreted correctly. The conflicts arise when the brain is unable to process information received from the eyes, so optical illusions are created in an attempt to interpret that information. As a result, our perception is skewed from reality.
There are three different types of optical illusions: literal illusions, physiological illusions and cognitive illusions. Literal optical illusions cause the eyes to perceive things that don’t actually exist. The brain creates an image that is different from what is truly there, trying to make sense of the visual stimuli by associating it with simple, familiar things. This is done by what is known as the “filling-in phenomena.” An example of this illusion is pareidolia- a phenomenon in which you see faces in everyday objects. By identifying something familiar, perhaps a face, the brain is able to understand what is being perceived.
In physiological illusions, an excessive amount of stimuli (light, colour, movement, brightness, size) disorients the brain’s senses. The repeating patterns of the images cause the visual system to become overloaded. For example, visualize what happens after one looks at an image with bright colours for a minute; when one looks away, one can see the afterimage. Even when the eyes no longer see the original stimulus, the afterimage is still shown due to the retinal photoreceptors in the eyes continuing to send neural impulses to the brain.
Cognitive illusions occur due to “unconscious inferences” and preconceived assumptions we have made about the world. These illusions are the most complex of all illusions and are typically divided into three categories: ambiguous illusions, paradox illusions, and distorting illusions. Ambiguous illusions are images that can cause the viewer’s perception to “switch” to a different interpretation. The viewer typically sees one of these interpretations at first but then visualizes the other after some thought. Paradox illusions involve objects that are impossible and paradoxical, such as the Impossible triangle, which can be depicted as a drawing, but never actually exist as a solid object. Distorting illusions are illusions in which the size, length, or position of two objects appear to be distorted; when in reality, the objects are the exact same. For example, the Café Wall illusion depicts straight horizontal lines, but the lines seem to be bent at first glance. Generally, cognitive illusions tend to blur the line between what you’re seeing and what you’re used to seeing, sparking the subconscious mind.
Although optical illusions are used to distort reality, scientists have been able to take advantage of that feature, making significant impacts in the real world. For example, video animation uses the “phi phenomenon”, an illusion in which a rapid series of still images appears as one continuous motion. In addition, during both world wars, warships were painted with bold stripes and patterns in an attempt to confuse the enemy. This paint scheme, known as “dazzle camouflage”, alters the brain’s perception of the range, speed, and direction of the ship, making it difficult for enemies to attack. Illusions also play a role in making Disney’s Sleeping Beauty Castle, which is only twenty-three meters high, look much taller. This is due to “forced perspective”, which makes an object look larger, smaller, farther away, or closer than it actually is.
For centuries, optical illusions have been the subject of fascination among philosophers, scientists, and psychologists. Although these illusions can be mystifying, they have revealed much about the inner workings of the brain, as well as how closely the brain and eyes work together to create perceptions about the world around us. But as we continue to experience the world with our senses, the brain will do its best to make sense of everything we encounter, no matter how confusing.
Educational Content:
Q: What are the three types of optical illusions?
A: Optical illusions typically fall under the categories of literal, physiological, and cognitive. When experiencing a literal optical illusion, the brain will attempt to fill in any gaps (filling-in phenomena) and make a guess about what is being seen.
Physiological illusions involve repeating patterns that overstimulate the photoreceptors in the eyes, affecting the brain and creating “afterimages”. Lastly, cognitive illusions are those that involve the higher-reasoning areas of the brain and are caused by unconscious inferences.
Q: What type of illusion is Rubin’s vase?
A: Rubin’s vase is a cognitive illusion, specifically an ambiguous illusion. Ambiguous illusions present the brain with multiple interpretations, which are usually easy to see and switch between. Rubin’s vase illusion depicts a black vase and two inward-looking faces; the visual system interprets and alternates between these figures by distinguishing the object (vase) from the background (faces).
Website Citations:
● https://www.wonderopolis.org/wonder/what-is-an-optical-illusion
● https://askabiologist.asu.edu/questions/what-causes-optical-illusions
● https://www.aao.org/museum-eye-openers/what-are-optical-illusions
● https://www.verywellmind.com/optical-illusions-4020333
● https://www.insidescience.org/video/how-do-optical-illusions-work
● https://psychology.wikia.org/wiki/Rubin_vase
● https://medicalxpress.com/news/2008-11-optical-illusions-eye-brain.html
Image Source:
● https://pixabay.com/vectors/cranium-head-optical-illusion-human-2858764/
● https://pixabay.com/vectors/optical-illusion-triangle-puzzle-311130/