Mutterings - are dogs color blind?
Probably one of the most frequently asked questions about dog's
vision is whether dogs see colors. The simple answer-namely that
dogs are colorblind-has been misinterpreted by people as meaning
that dogs see no color, but only shades of gray. This is wrong.
Dogs do see colors, but the colors that they see are neither as
rich nor as many as those seen by humans.
The eyes of both people and dogs contain special light catching
cells called cones that respond to color. Dogs have fewer cones
than humans which suggests that their color vision won't be as rich
or intense as ours. However, the trick to seeing color is not just
having cones, but having several different types of cones, each
tuned to different wavelengths of light. Human beings have three
different kinds of cones and the combined activity of these gives
humans their full range of color vision.
The most common types of human colorblindness come about because
the person is missing one of the three kinds of cones. With only
two cones, the individual can still see colors, but many fewer than
someone with normal color vision. This is the situation with dogs
who also have only two kinds of cones.
Jay Neitz at the University of California, Santa Barbara, tested
the color vision of dogs. For many test trials, dogs were shown
three light panels in a row--two of the panels were the same color,
while the third was different. The dogs' task was to find the one
that was different and to press that panel. If the dog was correct,
he was rewarded with a treat that the computer delivered to the cup
below that panel.
Neitz confirmed that dogs actually do see color, but many fewer
colors than normal humans do. Instead of seeing the rainbow as
violet, blue, blue-green, green, yellow, orange and red, dogs would
see it as dark blue, light blue, gray, light yellow, darker yellow
(sort of brown), and very dark gray. In other words, dogs see the
colors of the world as basically yellow, blue and gray. They see
the colors green, yellow and orange as yellowish, and they see
violet and blue as blue. Blue-green is seen as a gray. You can see
what the spectrum looks like to people and dogs below.
Color is only one of many visual stimuli that dogs detect in
their environment. Brightness, contrast, and especially motion, are
extremely important to a dog's interpretation of what it sees.