Purple has no dedicated wavelength of light like red or green. Our brains create the perception of purple when our eyes simultaneously detect red and blue light wavelengths. This makes purple a "non-spectral" color, a product of our visual system's interpretation rather than a distinct physical property of light itself. Essentially, purple is a neurological construct, a color our brains invent to bridge the gap between red and blue in the visible spectrum.
The intriguing proposition that the color purple exists solely as a construct of our minds, rather than a tangible property of the external world, forms the central thesis of the article "Purple Exists Only in Our Brains." The article elucidates this concept by delving into the physiological and neurological processes underlying our perception of color. It commences by explaining the nature of electromagnetic radiation and the visible light spectrum, a narrow band within this expansive spectrum to which our eyes are sensitive. Different wavelengths within this visible spectrum are interpreted by our brains as different colors. The article meticulously details how specialized photoreceptor cells in our retinas, known as cones, are responsible for color vision. Specifically, it focuses on the three types of cones – S, M, and L – each sensitive to short, medium, and long wavelengths of light, respectively.
The crux of the argument regarding purple's cerebral existence lies in its spectral composition, or rather, its lack thereof. Unlike colors like red, green, or blue, which correspond to specific single wavelengths of light stimulating individual cone types, purple arises from the simultaneous stimulation of both short and long wavelength cones (S and L), with minimal or no stimulation of medium wavelength (M) cones. This co-activation of non-adjacent cone types, with a gap in the middle of the stimulated spectrum, is unique to purple and is what sets it apart from other spectral colors. No single wavelength of light can elicit this specific pattern of cone activation. Therefore, the article argues, purple is a manufactured perception, a color our brains create in response to a particular combination of light wavelengths, rather than a color that exists independently in the external world as a single wavelength. The article further emphasizes this point by drawing an analogy to the perception of "magenta" or "pink," often used interchangeably with purple, which similarly results from a combination of spectral components.
The article proceeds to explore the evolutionary rationale behind this neurological construction of color. It suggests that the ability to perceive purple, even though it lacks a corresponding single wavelength, might have conferred an evolutionary advantage by enriching our visual experience and enhancing our ability to discriminate between different objects and surfaces in our environment. Furthermore, the article touches upon the subjective nature of color perception, acknowledging that the experience of "purple" might vary slightly between individuals due to subtle differences in their neural wiring and cone sensitivities. In conclusion, the article posits that while the physical stimuli that trigger the perception of purple are real and measurable, the color itself is a product of our brain's interpretation of these stimuli, a testament to the complex and fascinating interplay between the external world and our internal perception of it.
Summary of Comments ( 23 )
https://news.ycombinator.com/item?id=43583283
Hacker News users discuss the philosophical implications of purple not being a spectral color, meaning it doesn't have its own wavelength of light. Several commenters point out that all color exists only in our brains, as it's our perception of different wavelengths, not an inherent property of light itself. The discussion touches on the nature of qualia and how our subjective experience of color differs, even if we agree on labels. Some debate the technicalities of color perception, explaining how our brains create purple by interpreting the simultaneous stimulation of red and blue cone cells. A few comments also mention the arbitrary nature of color categorization across languages and cultures.
The Hacker News post titled "Purple exists only in our brains" (linking to an article on Snexplores) sparked a lively discussion with several interesting comments.
Many commenters focused on the philosophical implications of color perception being a construct of the brain. One commenter pointed out the distinction between the physical phenomena of wavelengths and the subjective experience of color, arguing that while wavelengths exist "out there," the experience of purple arises from our brains interpreting the simultaneous stimulation of red and blue cone cells. This doesn't mean purple "isn't real," but rather that its reality is different from the reality of electromagnetic radiation. Another commenter extended this idea to all sensory perception, suggesting that the "real world" is fundamentally different from our experience of it, as our brains create a model based on sensory input.
Several commenters delved into the specifics of color vision. One explained how purple is unique because it's not represented by a single wavelength of light, unlike other spectral colors. Instead, it's perceived when both red and blue cones are stimulated, a phenomenon referred to as "extra-spectral" color. Another commenter discussed the evolutionary reasons why we might have developed this particular system of color perception, suggesting it could be related to the importance of distinguishing ripe fruit against green foliage.
A couple of comments offered alternative perspectives on the article's central claim. One commenter argued that the title is somewhat misleading, as all colors, not just purple, exist only in our brains. They emphasized that the sensation of color is always a product of neural processing, regardless of whether it corresponds to a single wavelength or a combination. Another comment pointed out the inherent limitations of language when discussing subjective experience, noting that while we can use the word "purple" to communicate a shared perception, the actual subjective quality of that experience remains private and inaccessible to others.
Finally, a few comments took a more humorous approach. One commenter jokingly asked if this meant they could stop feeling bad about their fashion choices involving purple. Another playfully suggested that purple is "the gaslighting color." These lighter comments added a touch of levity to the otherwise philosophical and scientific discussion.
In summary, the comments on the Hacker News post ranged from in-depth explorations of color perception and the nature of reality to humorous reflections on the implications of the article's premise. The discussion highlights the fascinating intersection of physics, biology, and philosophy raised by the question of how we perceive color.