Let's do a fun little experiment:
Place the middle finger of one hand crossover on your index finger
Then use crossed fingertips to gently glide over the tip of your nose
Feel the sensation from your fingers
How's it going, do you feel like you have two noses?
图一图源:IASP2024
Touching the corner of your phone in the same way, or touching a small round object, such as a soybean, will also make you feel as if you have touched two objects.
In fact, this feeling is an illusion. It was discovered more than 2,000 years ago by the ancient Greek "encyclopedic" scientist Aristotle, so it is also known as the Aristotleillusion.
Figure 2: Aristotle mentions in Metaphysics (Τὰμετὰ τὰ φυσικά):
"When we cross our fingers, touch says there are two objects, while vision says there is one object. ”
(Vol. 4, Chapter 6) Source: Internet
How does the illusion come about?
The Aristotelian illusion is what is known as "perceptual separation". When we cross the index finger and middle finger, it is the outside of the two fingers that touches the nose, and the sense of touch is transmitted to the brain from these two sides.
Since the inside of the two fingers is normally touched, and the outside of the two fingers almost never touches the same object at the same time, the brain "takes it for granted" that it touches both noses.
Figure 3 touches the tip of the nose on the outside of two fingers Source: Lhecht
The answer to this phenomenon can also rise to the philosophical level. Merleau-Ponty, a French philosopher and master of phenomenology, believes that the "Aristotelian illusion" is related to the body schema: the body schema can be simply understood as the body's movement habits and perceptual possibilities. Movement habits and perceptual possibilities refer to the actions that the subject usually performs and is capable of performing, while crossing the fingers is a "human action" that goes beyond the possibility of natural finger movement.
For this reason, body schemas are unable to point crossed fingers as an organ to the same movement item or intention. Thus, the two fingers that cross act separately and produce a separate sensation that cannot be unified in one perception.
Why is the brain so prone to delusions?
Nobel laureate and cognitive psychologist Daniel Kahneman argues that evolution has made the brain very stingy with the allocation and use of cognitive resources. And in order to cope with the rapidly changing world, the brain often chooses to sacrifice part of the "correctness" in exchange for "speed". How does this work? And that is through experience.
"Experience" is a computational shortcut built by the brain in pursuit of speed. With certain pre-established pre-assumptions, the brain can save a lot of resources. For example, the brain presets the near, big, and far of things;
Figure 4 Do you feel that the monster in the back is bigger than in the front?
In fact, they are the same size Source: Internet
The brain presupposes that the color of the object itself usually does not change arbitrarily, and if it does, it is because of the brightness or color of the light source.
Picture 5 Classic old picture: Is the dress you see blue-black or white-gold?
Source: Internet
These experiences are experiences because these qualities (e.g., near and far) are constant in most cases, and they help us to quickly recognize and understand the world. So in the process of evolution, they became the brain's intrinsic way of extracting information.
However, there are always exceptions, such as these artificially constructed "unnatural things" and "unnatural actions" mentioned above, if the brain still understands them in an inherent way at this time, it will produce illusions and make us "deceived". This can also be understood as a bug due to the imperfect evolution of the brain.
Figure 6 Source: Network
Illusion also contributes
Despite being seen as a bug in the brain, delusion has a non-negligible contribution in many areas. For example, scientific research can provide scientists with a unique perspective on how the brain processes information, constructs perceptions, and makes decisions, which is important for advancing fields such as cognitive science, psychology, and neuroscience.
Figure 7: Aristotelian delusion contributes to Parkinson's disease research Source: Brain
In interior design or architectural planning, illusion is also often used by designers to alter the perception of space. For example, by using mirrors or color combinations, small spaces can look more spacious and comfortable. For those who live in big houses, this one can skip the bushi.
Figure 8: Glass doors increase the sense of transparency Image source network
And in film and animation production, the illusion is also an "old actor". The famous Hitchcock zoom is essentially an application of optical illusions. By zooming in or out of the camera lens, the background appears to be squeezed or stretched while keeping the foreground in the same position. So that we get a wonderful feeling when watching the movie.
Figure 9 Hitchcock Zoom Source: See watermark
The Aristotelian illusion is just one of many delusional phenomena that reveal the limitations of our brain's perception of the world. However, it is precisely these limitations that push us to constantly explore, research, and improve our cognitive system. At the same time, let us realize that science is not an unreachable and mysterious realm, it is actually hidden in our daily lives.
Bibliography:
- 《Judgementunder uncertainty: Heuristics and bias》
- Aristotle’sillusion and the enactive embodied situated approach to perception
- Aristotle’sIllusion in Parkinson’s Disease: Evidence for Normal InterdigitTactile Perception | Brain | Oxford Academic
- HTTPS://Psychologists.Blog.Gustaves.seven/2020/04/09/a-hands-down-simple-illusion-the-aristotelle-illusion/
Author: Cheng Xin, Master of Social Psychology with a major in sociology, Beijing Normal University
Review: Li Xiran, Psychological Counselor, Master of Psychoanalytic Theoretical Studies, University College London
Editor-in-charge: Dong Xiaoxian