The genetics of superhuman vision

Most humans are trichromats, perceiving color through three types of retinal cone cells. These cones—S, M, and L—are sensitive to short (blue), medium (green), and long (red) wavelengths of light, respectively. The brain combines signals from these three channels to distinguish approximately one million different colors. Tetrachromacy is the presence of a fourth type of cone cell, forming a fourth channel for color information and expanding the number of perceivable colors to an estimated 100 million.

The biological potential for tetrachromacy is linked to the X chromosome. The genes that code for the M- and L-cone photopigments, OPN1MW and OPN1LW, are located on this chromosome. Because women have two X chromosomes, they can inherit different versions (alleles) of these genes. If one X chromosome carries the genes for the standard M and L cones, and the other carries a mutated version that produces a photopigment with a different spectral sensitivity, the woman's retina can end up with four distinct cone types. This genetic possibility is more likely in women who are carriers for color blindness, which is why researchers often seek out mothers of colorblind sons for their studies.

The search for a functional tetrachromat

For decades, the existence of functional human tetrachromacy was only a theory. At Newcastle University, neuroscientist Dr. Gabriele Jordan led a search that spanned more than 20 years to find a woman who possessed the four cone types but whose brain could also process the extra visual information. The team screened women who were carriers of anomalous trichromacy (a mild form of color blindness).

In 2010, the team identified the first person proven to have functional tetrachromacy, a physician in northern England identified in studies only as cDa29. To test her abilities, researchers used a specially designed device that presented three colored circles of light. To a standard trichromat, the circles appeared identical. Subject cDa29, however, could consistently distinguish them, demonstrating her superior color discrimination abilities. The discovery showed that the human brain can process information from a fourth cone type. Another confirmed tetrachromat, the artist Concetta Antico, reports perceiving thousands of variations in a single color, like green, and uses this ability to create paintings with bright color palettes.

Practical Information

Opening Hours

The Institute of Neuroscience is a university research facility and is not open for general public tours. The university campus itself is open to walk through.

Admission

Not applicable for public visits. Self-guided tours of the Newcastle University campus are free.

Accessibility

The University campus is located in the city center and consists of paved walkways, accessible to wheelchairs.

Website

Visit website →

A Fourth Cone for 100 Million Colors

The genetics of superhuman vision

The search for a functional tetrachromat

💡Fun Facts

References

There's more in the app

Practical Information

A Fourth Cone for 100 Million Colors

The genetics of superhuman vision

The search for a functional tetrachromat

💡Fun Facts

References

There's more in the app

Practical Information

Nearby curiosities

Nearby curiosities