Color Perception: The Brain's Interpretation and the Boundaries of Illusion

We humans perceive the world in a rich tapestry of colors. However, these "colors" do not have a physical existence. They are the brain's interpretation of electrical signals generated when light reflects off objects and its wavelengths stimulate the photoreceptor cells in the retina. In this article, we will explore how humans perceive color and whether it can be considered an illusion, from the perspectives of neuroscience, psychology, and philosophy.

The Mechanism of Color Vision

Color vision is mediated by photoreceptor cells called cone cells in the retina. There are three types of cone cells (short-wavelength, medium-wavelength, and long-wavelength), each sensitive to different wavelengths of light. The combination of their responses allows us to discriminate a wide variety of colors.

Signals from the cone cells are transmitted through the optic nerve to the visual cortex in the brain. In the visual cortex, the signals are processed and ultimately perceived as "color." This process is not merely a passive transmission of signals but an active interpretation by the brain.

The Brain's Interpretation and Color Constancy

The brain has the ability to adjust our perception of color in response to changes in the surrounding environment and lighting conditions. For example, a white sheet of paper appears white both under sunlight and under electric light. This phenomenon, known as color constancy, occurs because the brain compensates for the color temperature of the light source.

Color constancy is an essential function that allows us to maintain a stable perception of color. However, this function also suggests that the colors we see do not necessarily reflect physical reality.

Color as an Illusion

An illusion is a phenomenon in which there is a discrepancy between sensory stimuli and perceptual experience. Phenomena such as color constancy and the appearance of colors changing depending on surrounding colors can be considered a type of illusion.

For instance, the same shade of gray may appear greenish when surrounded by red and reddish when surrounded by green. This is an illusion called the color contrast effect. Additionally, when colors of the same hue but with different brightness or saturation are arranged together, the difference in color may be perceived as greater than it actually is. This is an illusion called the color assimilation effect.

Philosophical Considerations: What is Color?

The existence of color constancy and illusions leads to the fundamental question: What is color? Color is not a physical entity but a subjective sensory experience created by the brain.

The philosopher John Locke (1632-1704) called color a secondary quality, defining it as a quality that exists only in the mind of the observer, not a property inherent in the object itself. On the other hand, the philosopher George Berkeley (1685-1753) argued that everything that exists is perceived, and color is perception itself.

Conclusion

The "colors" that humans see are the result of the brain's interpretation of light information and are subjective sensory experiences that do not necessarily correspond to physical reality. Color constancy and illusions demonstrate how active a role the brain plays in color perception.

The question of what color is requires not only scientific inquiry but also philosophical consideration. It is a complex issue. However, the pursuit of this question will provide us with important clues to understanding how we perceive the world and what we ourselves are.