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Orange you glad? Fido sees the blues.

Orange you glad? Fido sees the blues

Gerald Jacobs was more than a little surprision science program casually television science program casually stated that dogs lack color vision. An experimental psychologist at the University of California, Santa Barbara, Jacobs had spent a good part of his career seeking color vision in animals, and to his knowledge the question remained far from settled for canines.

A literature search confirmed that the most recent investigation -- a 1969 study finding some evidence of color discrimination in dogs -- was less than complete and that previous findings were split about fifty-fifty. So, with colleagues Jay Neitz and Timothy Geist, Jacobs embarked upon the most definitive study to date.

Armed with a sophisticated, computer-controlled apparatus that measures spectral thresholds, analyzes wavelength discrimination and delivers beef-and-cheese-flavored food pellets, the researchers enlisted a couple of greyhounds and a poodle in a series of behavioral experiments. Now they report their results: The faithful companion fetching your daily newspaper can indeed see some beauty in those Sunday comics.

"These experiments lead to the straightforward conclusion that dogs have color vision," the team writes in the September VISUAL NEUROSCIENCE. But unlike people, whose color-sensitive retinal cells detect blue, green and red, man's best friend paints the world with a two-tone palette. Indeed, the researchers find, canine color vision resembles that of humans with deuteranopia, or red-green colorblindness. One in 100 U.S. males inherits this syndrome, which leaves them unable to discriminate among green, yellow, orange and red. Blue stands out well from these other colors. "What it does effectively is divide the spectrum in half," Jacobs says. In comparison, normal humans and most primates construct their visual world from three basic colors; recent research suggests some birds use four.

Jacobs cautions that the experiments reveal little about how the world actually appears through a dog's eyes. For example, a dog may literally see red (that is, what humans would call red) when looking at Garfield the cat, who seems orange to normal humans and who often looks yellow to deuteranopes.

"What these experiments measure is the animal's ability to make discriminations. But we have no way of knowing what the experiences are associated with those discriminations," Jacobs says. Colors, he notes, "come with a lot of semantic baggage."
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Title Annotation:color vision in animals
Author:Weiss, R.
Publication:Science News
Date:Sep 30, 1989
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