Contrary to what we once thought, dogs aren't limited to a world of blacks, whites, and greys; in fact, they can recognize the color of an object better than the brightness of it. In a study published Wednesday in the Proceedings of the Royal Society B, a team of Russian researchers reported that dogs have the ability to see color.
Researchers began the experiment by placing four boxes in front of each dog. Each box contained a small piece of meat and was labeled either light blue, dark blue, light yellow, or dark yellow. However, only one of the boxes was unlocked and labeled the same color for each trial, allowing dogs to recognize which one contained the meat. The dogs quickly learned which color coordinated with the unlocked box of meat, and repeated training 10 times a day for nine days.
After researchers realized the dogs could clearly learn which color associated with the accessible food source, they changed the box's label. The dog that had learned a dark yellow paper meant accessible meat was given only the choices of dark blue or light yellow. If the dog chose the dark blue labeled box, it indicated to researchers that the dog based its decision on brightness and shade. But it turns out that the dog didn't choose the dark blue box and chose the light yellow box instead. The team thus concluded that the dog's meat association was based off of color and not brightness.
After all of 90 trials, the researchers found more than 70 percent of all dogs based their decision off of color and not brightness of the label. Six out of the eight tested dogs used color to identify the meat-accessible box, 90 to 100 percent of the time. Although it was a small sample size of mixed breeds, the overwhelming majority of dogs used color to determine which box would lead them to the meat.
Researchers were satisfied with their conclusive results. And, if they could expand their findings on a larger scale in the future, professional dog trainers and eye dog trainers could potentially gain valuable information. Currently, such trainers avoid using colors as cues or reward-based systems, relying solely on brightness and shade.
The common misconception of dogs' color capacity stems from the animal's short supply of color receptors, commonly known as cones. Humans have three cones while dogs only have two, giving us a wider variety of color to choose from. Each cone is sensitive to a different wavelength of light, each of which is combined into different amounts and creates all the hues of the color wheel. This works the same way as taking the three primary colors — red, green, and blue — that are used when projecting light through the retina (eyes lens) and mixing them together to create a wide-range palate of shades and hues. But because dogs only have two cones, their ability to see color is limited and comparable to a human with a red-green colorblindness, which is a result of being born with only two cones as well. Nevertheless, while the matter of two cones rather than three is true for dogs, it's obvious that they're better perceivers of color than we thought.
Source: Badridze J, Kasparson A, Maximov V. Colour cues proved to be more informative for dogs than brightness. Proceedings of the Royal Society B. 2013.