All dog owners know the look, that sweetly urging expression capable of convincing even the hungriest human to break down and share a bit of their sandwich. But as uncontrived as those "puppy-dog eyes" appear, new research suggests that face may have been honed over thousands of years as way of winning us over - and it still works like a charm.
In a study from the University of Portsmouth, researchers found potent power in pooches' upturned brow, giving them the appearance of bigger, innocent-seeming eyes - likening the endearing look to that of a human child.
After examining the eye movement of 27 shelter dogs in need of a new home, it was discovered that the frequency with which they made these "childlike expressions" correlated with a higher rate of adoption. Humans, it seems, are more drawn to pets that make this look, thus improving their chances of survival historically.
Researchers believe that in the early days of canine domestication, "wolves which produced childlike expressions may have been more tolerated by humans, and so modern dogs have inherited these features," says Dr. Bridget Waller.
"Our study suggests that dogs' facial movements have evolved in response to a human preference for childlike characteristics. In other words, we might have automatically opted for dogs which produced facial movements that enchanted their baby-like faces."