Professor of IPB University: What Our Eyes See Is Not Actual Reality, Only Brain Perception

Many people think that what they see is the objective reality of the world around them. However, according to IPB University Professor of Theoretical Physics, Prof Husin Alatas, human visual perception is actually the result of a complex construction of the brain that is predictive, not a direct reflection of physical reality.

In his explanation, Prof Husin said that what is seen by the human eye is the result of the interaction between visible light and photoreceptor cells in the retina.

“Light entering the eye is focused by the lens, then activates photoreceptor cells that produce electrical signals in the form of action potentials. This signal is relayed to the visual cortex in the hindbrain through the optic nerve system, producing an inverted image,” he explains.

The image is then processed through complex coordination involving many parts of the brain, before finally being perceived predictively by the prefrontal cortex structure in the forebrain. “One of the results of this process is the color perception of objects,” added the lecturer of Optics & Photonics and Biophysics & Complexity at the Department of Physics, IPB University.

Prof Husin explained that visible light itself is only a small part of the electromagnetic wave spectrum. In physics, the light is characterized by wavelength. Interestingly, light with certain wavelengths actually has no color.

“Color is the perception of the brain. Three types of cone photoreceptor cells in the retina of the human eye respond to three wavelength ranges and produce the perception of red, green, and blue colors,” he adds.

He adds that if one wavelength activates two types of cones at once, the brain combines them into a new color. For example, if a wavelength triggers both red and green cells, it will be perceived as yellow. Meanwhile, if all three types of cones are activated together, the brain perceives the color as white.

However, in low lighting conditions, cone cells are inactive because they require high light intensity. This is where the role of rod cells takes over, which are only able to provide the perception of graded gray to white colors. “This is why the eyes in dim lighting cannot see colors,” he added.

Prof Husin explained that some people who are blessed with the privilege of not having certain types of cone cells will certainly see a different color reality from those who do not have them.

“Some animals or insects have different numbers of photoreceptor cell types and sensitivity ranges, so practically they also have different realities,” he said.

For example, bee insects have sensitivity in the ultraviolet wavelength, so bee eyes can provide color perception at that wavelength.

Prof Husin explained that the perception generated by the brain is predictive, reinforcing the statement that what is seen by the eye is not the actual reality.

This can be proven through the phenomenon of optical illusions, such as the length of two straight lines that are actually the same but look different if at both ends of the first line an arrow is given in the opposite direction to the arrow at both ends of the second line. (dr) (IAAS/ASY)