Tetrachromacy

Tetrachromacy is a condition of possessing four independent channels for conveying color information, or possessing four types of cone cells in the eye. Organisms with tetrachromacy are called tetrachromats.

Overview

In tetrachromats, the sensory color space is four-dimensional, meaning that matching the sensory effect of arbitrarily chosen spectra of light within their visible spectrum requires mixtures of at least four primary colors.

Tetrachromacy is demonstrated among several species of birds, fish, amphibians, reptiles and insects. It was also the normal condition of most mammals in the past; a genetic change made the majority of species of this class lose two of their four cones to become dichromats. However, it is believed that some female humans may be tetrachromats.

Human tetrachromacy

The possibility of tetrachromacy in humans is made possible by genetic variation at the L-cone and M-cone pigments. It appears that some 12% of women may have an extra type of color receptor because they have two different forms of the gene for the L-cone or the M-cone (which lies on the X chromosome). This would provide the necessary genetic mechanism for tetrachromacy.

See also

• Color vision
• Trichromacy
• Dichromacy
• Monochromacy

External links

• BBC - Future - The women with superhuman vision

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  Bird visual pigment sensitivity
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  Cones in the human eye
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  Tetrachromacy