Intelligence in Nature - Jeremy Narby [88]
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P. 111: BUTTERFLIES SEE IN COLOR
Kinoshita et al. (1999) write: âThe butterflies were trained to feed on sucrose solution placed on a disk of a particular color in a cage set in the laboratory. After a few such training runs, a butterfly was presented with the training color randomly positioned within an array of disks of other colors, but with no sucrose solution. The results indicate that the butterflies learn rapidly to select the training color reliably among different colors. The training color was also correctly selected when it was covered with neutral density filters to reduce its brightness, or even when the color was presented together with disks of a variety of shades of gray. These results demonstrate convincingly, for the first time, that a butterfly has true color visionâ (p. 95).
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P. 111: BUTTERFLIES HAVE COLOR CONSTANCY
Kinoshita and Arikawa (2000) write: âColor vision is the ability to discriminate visual stimuli on the basis of their chromatic content regardless of their brightness. The reliability of color vision is reinforced by the phenomenon of color constancy, which enables animals to recognize an objectâs color irrespective of the spectral content of the illuminating light. For example, to a human observer, a red apple appears red both in sunshine and in fluorescent light, although the irradiation spectra are distinctly different. This phenomenon is the color constancy of human visionâ (p. 3521). They add: âWe trained newly emerged Papilio xuthus to feed on sucrose solution on a paper patch of a certain color under white illumination. The butterflies were then tested under both white and colored illumination. Under white illumination, yellow-and red-trained butterflies selected the correctly colored patch from a four-color pattern and from a color Mondrian collage. Under four different colors of illumination, we obtained results that were fundamentally similar to those under white illumination. Moreover, we performed critical tests using sets of two similar colors, which were also correctly discriminated by trained butterflies under colored illumination. Taken together, we conclude that the butterfly Papilio xuthus exhibits some degree of color constancy when searching for foodâ (p. 3521).
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P. 112: RICHLY ENDOWED VISUAL SYSTEM OF BUTTERFLIES
The quote in the main text is from Arikawa et al. (2004) which examines color vision and retinal organization in butterflies.
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P. 112: BUTTERFLIES SEE IN ULTRAVIOLET, HUMANS DO NOT
Arikawa (1999) writes: âThe human color vision system is so-called trichromatic, which is based on three types of cone photoreceptors, peaking in the blue, green, and red wavelength regionâ¦A striking difference exists in the color vision systems of arthropods and humans, namely in the sensitivity to UV light. The absence of UV sensitivity in the human eye makes it difficult to imagine the visual world of arthropods, for the human observer is virtually blind to the many patterns in natural scenes produced by UV reflection and absorptionâ (p. 23).
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P. 113: HUMAN VISION AND COLOR-BLINDNESS
Ensminger (2001) writes: âThe colors we see depend on the wavelength sensitivities of the visual receptors within our eyes as well as the wavelengths of light that enter our eyes. In color vision light excites different classes of photoreceptor cells, containing different visual pigments, and the brain compares their differential light absorption. Thus in bright light humans see a colorful world because the cone cells in our retinas have three visual pigments, with maximal sensitivities in the blue (±425nm), green (±530nm), and red (±560nm) regions of the spectrum, and the differential responses of these cells enables color visionâ¦The importance of our visual pigments in determining the perception of color is perhaps best illustrated by âcolor-blindness.â This genetic disorder, which occurs in about one of twelve males and one of one hundred females, is caused by