GC: n
S: MEDNT – https://www.medicalnewstoday.com/articles/daltonism-color-blindness (last access: 6 September 2025); SDir – https://www.sciencedirect.com/science/article/abs/pii/S104160800400041X (last access: 6 September 2025).
N: 1. Daltonism: red-green color blindness occurring as a recessive sex-linked genetic trait; broadly: any form of color blindness.
- Eponym from family name Dalton. 1920 in reference to a plan or system of school education designed by Helen Parkhurst, from Dalton, Massachusetts, U.S., where it was first adopted. For Daltonism (a reference to English chemist John Dalton), see color-blindness. Daltonian, in reference to Dalton’s work, is attested by 1813.
- color-blindness, also colour-blindness, “incapacity for perceiving certain colors due to an absence or weakness of the sensation upon which the power of distinguishing them depends,” 1844, the native word, used in England instead of French daltonisme (by 1828), after English chemist John Dalton (1766-1844), who published a description of it in 1794. From “color” (n.) + “blindness”.
2. colour blindness, also known as color blindness. Inability to distinguish one or more of the three colours red, green, and blue. Most people with colour vision problems have a weak colour-sensing system rather than a frank loss of colour sensation. In the retina (the light-sensitive layer of tissue that lines the back and sides of the eyeball), humans have three types of cones (the visual cells that function in the perception of colour). One type absorbs light best in wavelengths of blue-violet and another in the wavelengths of green. The third type is most sensitive to longer wavelengths—more sensitive to red. Normal colour vision, when all three cone types are functioning correctly, is known as trichromacy (or trichromatism).
3. Visual Disorders: color blindness, daltonism.
- A term colloquially and incorrectly applied to any deviation from normal perception of hues.
4. Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to “blindsight” for color or an instance of “covert” processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to chromatic contrast and motion in equiluminant displays. Moreover, visually evoked cortical potentials can still be elicited in response to chromatic stimuli. We suggest that these demonstrations reveal intact residual processes rather than the operation of covert processes, where proficient performance is accompanied by a denial of phenomenal awareness. We sought evidence for such covert processes by conducting appropriate tests on achromatopsic subject M.S. An “indirect” test entailing measurement of reaction times for letter identification failed to reveal covert color processes. In contrast, in a forced choice oddity task for color, M.S. was unable to verbally indicate the position of the different color, but was surprisingly adept at making an appropriate eye movement to its location. This “direct” test thus revealed the possible covert use of chromatic differences.
S: 1. MW (last access: 6 September 2025); Etymonline (last access: 6 September 2025). 2. EncBrit (last access: 6 September 2025). 3. TERMIUM PLUS (last access: 6 September 2025). 4. SDir (last access: 6 September 2025).
SYN: color blindness, color-blindness, colour blindness.
S: Etymonline (last access: 6 September 2025); TERMIUM PLUS (last access: 6 September 2025); EncBrit (last access: 6 September 2025).
CR: achromatopsia
