Today, dark eyes are more common in domestic dogs, and this may not be a coincidence! The fact is that people perceive this trait as more friendly.
Since the domestication of dogs, which occurred about 15,000 to 50,000 years ago, humans have begun to select certain traits in them.
Among these traits, it seems, were the "puppy eyes." Previously, scientists discovered that dogs developed specific facial muscles that allow them to maintain a sad expression, which triggers a desire in people to care for them.
Modern studies suggest that humans may have influenced the eye color of dogs as well. Research conducted by scientists in Japan showed that dark eyes are more common in domestic dogs than in their wild counterparts, and that people perceive dogs with dark eyes as more friendly.
What the Study Says
Researchers noted that later breeding of certain breeds may also have affected the eye color of dogs: for example, the blue merle coat color observed in breeds like Shetland Sheepdogs and Border Collies is associated with blue eyes.
However, when comparing the eyes of wolves and modern dogs, clear patterns can be seen. Scientists analyzed the iris color in 22 images of gray wolves with various coat colors, as well as photographs of 81 domestic dogs. As a result, they found that the latter generally have darker eyes with a more reddish hue.
To understand how this affects people, the authors created 12 pairs of images, where one photo depicted a domestic dog with light eyes, and the other showed the same dog with dark eyes. These pairs were shown to 76 participants, who were asked to evaluate the dogs on various personality traits and how much they would like to interact with them or keep them.
The team found that dogs with dark eyes received higher ratings for friendliness than dogs with light eyes and were considered calmer, more sociable, and more dependent on humans, as well as less aggressive, intelligent, and mature. Similar results were obtained when the survey was repeated with 66 participants.
