The Color You See When You Close Your Eyes Is Not Black: Eigengrau

Have you ever wondered if the color you see when you close your eyes and stay in the dark is not actually true black? Most of us think that when we close our eyes, we see a complete "absolute black" as if a screen has been turned off. However, the visual perception mechanism of the human eye and brain works in a much more complex and different way than a digital camera. According to scientists, even in complete darkness, our mind never acts like a completely blank screen. In reality, when we close our eyes, our brain makes us perceive a non-existent color as if it were a natural one.

This interesting and unique perceptual state is called "Eigengrau" in the scientific world. The famous physicist and psychologist Gustav Theodor Fechner, who lived in the 19th century, defined this tone seen when the eyes are closed in this way. Eigengrau, a word of German origin, means "intrinsic gray" or "internal gray". This color we cognitively see is a dark gray with a slightly bluish tone, and it may even sometimes have a dynamic texture covered with small points of light or glows. In digital color codes, this special tone is represented closely by the value #16161D.

As can be understood from the code #000000, which is the digital equivalent of absolute black, Eigengrau is actually a lighter tone than pure black. The main reason for this is that the human brain cannot physiologically perfectly replicate absolute black, and it somehow adapts itself to this situation. Various scientific studies prove that even if no light stimulus comes from the outside, the brain does not completely stop its functions. Therefore, Eigengrau is actually a color that does not exist physically, but which we experience as if it were real, resulting from the constant functioning of the human brain's visual system.

The fundamental biological mechanism underlying this situation is that the photoreceptors in the retina, namely the rod and cone cells, never completely shut down. Even in complete darkness, these cells continue to produce electrical signals called "dark noise". According to research published in the Nature journal in the 1990s, this situation is mainly caused by the rhodopsin molecule reacting to heat. In other words, the human body's own heat can stimulate the eye cells into action without any external light. These misleading stimuli cause a visual tone, which has no connection with real-world images, to be continuously transmitted to our brain.

On the other hand, the neurological responses of the visual cortex in our brain to black and white surfaces are also quite different from each other. A study conducted by experts from New York University and Pekin University on monkeys and published in the Proceedings of the National Academy of Sciences (PNAS) journal in 2014 illuminates the details on this subject. While the relevant nerve cells in the brain remain active when looking at a black surface, inhibitory mechanisms come into play when looking at white, and the activity of the neurons decreases significantly. In the light of all these scientific facts, the next time you close your eyes to rest them, instead of saying that everything is black, it will be quite pleasant to notice this mysterious Eigengrau experience created by your brain.