Let's try a fun little experiment: Cross the middle finger of one hand over the index finger, then gently slide the crossed fingertips over the tip of your nose. Pay close attention to the sensation in your fingers. Does it feel like you're touching what seems like two noses?
In the same way that you touch one corner of your phone, or a small circular object like a soybean, you'll feel as though you're touching two objects.
This sensation is actually an illusion, first observed over two millennia ago by the ancient Greek "encyclopedic" scientist Aristotle, hence also known as the Aristotle illusion.
In Aristotle's Metaphysics, he mentions: "When we cross our fingers, touch tells us there are two objects, but sight tells us there is one." Image Source: Internet
How are illusions created?
Aristotle describes illusions as a phenomenon of "perceptual segregation." When we cross our index and middle fingers, the sides of these two fingers touch the nose, and sensory input from these two sides is separately transmitted to the brain.
Under normal circumstances, the inner sides of these fingers touch the nose, and the outer sides of the two fingers rarely touch the same object simultaneously. Consequently, the brain "jumping to conclusions" assumes it has touched two noses.
Image 3: The two fingers touching the tip of the nose are the outer sides of two fingers. Image source: lhecht
The explanation for this phenomenon can also rise to a philosophical level. French philosopher and phenomenology master Maurice Merleau-Ponty believed that the "Aristotle illusion" is related to the body schema:
The body schema can be simply understood as the habitual movements of the body and the possibilities of perception. Habitual movements and possibilities of perception refer to the actions that a subject usually performs and can perform, while crossing fingers is a "deliberate action" that goes beyond the natural movements of the fingers.
For this reason, the body schema cannot treat crossed fingers as an organ pointing to the same movement or intention. Therefore, the two crossed fingers act separately and produce separate sensations that cannot be unified in a single perception.
Why is the brain so prone to illusions?
Nobel laureate and cognitive psychologist Daniel Kahneman believes that evolution has made the brain very stingy in allocating and using cognitive resources, "if it can avoid thinking, it will." And in order to cope with the ever-changing world, the brain often chooses to sacrifice some "accuracy" in exchange for "speed." How is this achieved? Through "experience."
"Experience" is a computational shortcut that the brain has built to pursue speed. Through certain pre-established assumptions, the brain can save a lot of resources. For example, the brain assumes that objects are larger when they are close and smaller when they are far away.
In Figure 4, do you think the monster in the back is larger than the one in the front? In fact, they are the same size. Image Source: Internet
The brain tends to perceive objects with their inherent colors unchanged. Any apparent alterations typically stem from changes in lighting or color.
Image 5 Classic Old Picture: Do you see the dress as blue-black or white-gold? Image Source: Internet
These experiences become experiences precisely because the qualities mentioned above (such as near-big far-small) are generally constant and unchanging in most situations. They help us quickly perceive and understand the world. Therefore, during the process of evolution, they have become the brain's inherent way of extracting information.
However, there are always exceptions. For example, the "unnatural things" and "unnatural actions" constructed by humans in the previous text. If the brain still tries to understand them using its inherent methods, illusions can occur, causing us to be "tricked." This can also be understood as bugs that arise due to the brain's evolution not being perfect.
Figure 6 Image Source: Internet
Illusions also contribute
Despite being considered bugs of the brain, illusions have significant contributions in many fields. For example, in the realm of scientific research, they offer scientists a unique perspective, aiding in their understanding of how the brain processes information, constructs perceptions, and makes decisions. This is crucial for advancing fields such as cognitive science, psychology, and neuroscience.
Image 7 Aristotle's Illusion contributes to Parkinson's disease research. Image source: Brain
In interior design or architectural planning, illusions are also often utilized by designers to alter spatial perception. For example, clever use of mirrors or color combinations can make a small space appear larger and more comfortable. For friends living in large houses, you can just skip this one.
Figure 8: Glass doors enhance transparency. Image source: Internet
In film and animation production, illusion plays a starring role. The famous "dolly zoom," pioneered by Alfred Hitchcock, fundamentally relies on visual illusion. By zooming the camera lens in or out while simultaneously moving the camera to keep the foreground constant, the background appears compressed or stretched. This creates a mesmerizing effect for viewers during the film.
Figure 9: Hitchcock Zoom. Image source: See watermark.
The Aristotle illusion is just one of many perceptual phenomena, revealing the limitations of our brain's perception of the world. However, it is these very limitations that drive us to continually explore, study, and refine our cognitive systems. At the same time, it makes us realize that science is not an elusive mystery but rather hidden in the everyday occurrences of our lives.
