One of the most persistent errors about dogs is the claim that they are colorblind. It has been known for decades that dogs can see colors, but research into the details of how they use their color vision can still reveal new information. In a recent study called “Colour cues proved to be more informative for dogs than brightness”, researchers asked the simple question, “Do dogs attend to color or brightness when learning the cues that indicate the presence of food?
In the experiment, researchers trained dogs to make a choice between boxes concealing food. The boxes were each marked with a colored paper, and the dog had to learn which one indicated a piece of meat was inside. Dogs were trained to discriminate between either light yellow and dark blue or between dark yellow and light blue. Then the dogs were tested to see if the cue they used to make correct choices was the color of the paper or the brightness of the paper.
For example, a dog who had learned to choose the box marked by a dark yellow piece of paper was tested with a choice between a box marked by light yellow or a box marked by dark blue. The experimenters were asking whether the dog had learned that “dark” indicates the presence of meat or whether “yellow” does. They found that dogs were making choices based on color, not brightness, in the majority of cases. It was a small sample size of only 8 dogs, but it suggests that dogs not only see color, which has long been known, but that they pay attention to it more than to the depth of color.
It is not surprising that if dogs have the ability to see color that they would use that color functionally in various situations. Asking whether dogs distinguish dark from light when the opportunity to distinguish by color is also present may be an important preliminary step in understanding what dogs attend to. However, I would be even more interested to know whether dogs favor color over shape, color over size or even color over various sounds to make their choices, as all of these seem more biologically relevant to dogs seeking food than brightness does.