For many decades, scientists believed dogs could only see in monochrome and that they used brightness levels - whether something looked lighter or darker next to another object - to identify outlines of items and to use brightness levels to see the outlines of items.

But now Russian scientists have not only proved that dogs do have a limited color range, but that they also use this color spectrum to distinguish between objects and to select certain items.

Originally scientist Jay Neitz from the University of Washington, carried out experiments last year on dogs to test this theory. Neitz knew that the human eye has three 'cones' that can detect color and can identify red, blue, green and yellow wavelengths created by light entering the eye. He discovered that dogs only have two cones which means they can distinguish blue and yellow, but not red and green. This is the same spectrum seen in humans when they have colorblindness.

Then a team of researchers from the Laboratory of Sensory Processing at the Russian Academy of Sciences tested the sight of eight dogs of varying sizes and breeds. They wanted to expand on the work of Neitz from the University of Washington last year.

The Russian scientists therefore printed four pieces of paper in different colors; dark yellow, dark blue, light yellow and light blue. They used the dark and light hues to test the theory that dogs use brightness levels to distinguish between items.

In the first test, researchers took a dark yellow and light blue sheet of paper, as well as a dark blue and light yellow combination and put them in front of food bowls placed inside locked boxes. Then they unlocked one of the boxes and put the dark yellow piece of paper in front of the box containing a piece of raw meat in each trial. Each test involved the dogs being allowed to try to open one box before being taken away.

Only three trials were needed for the dogs to learn which color paper was put in front of the box containing the raw meat. Once the dogs could identify that a piece of dark yellow paper meant meat was nearby, the scientists wanted to check whether the animals were choosing this paper because of its brightness or its color.

To test this they put the dark blue paper in front of one box and light yellow in front of another. If the dogs chose the dark blue paper, the scientists could rule that the animals were making choices based on brightness. The dogs had been trained that dark yellow paper was always put in front of bowls containing meat. But even when light yellow paper was used, the dogs still found the meat meaning they used color rather than brightness when making their decisions.

Each dog chose the light yellow paper which meant that they were making choices based on color more than 70 per cent of the time. Six out of the eight dogs made the color choice between 90 and 100 per cent of the time.

The Russian researchers concluded that: 'We show that for eight previously untrained dogs color proved to be more informative than brightness when choosing between visual stimuli differing both in brightness and chromaticity. Although brightness could have been used by the dogs in our experiments, it was not. Our results demonstrate that under natural photopic lighting conditions color information may be predominant even for animals that possess only two spectral types of cone photo-receptors.'

Be sure to watch the video below on this. 
VIDEO Dogs Can See in Color

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