How canines capture your heart: scientists explain puppy dog eyes

Study finds animals developed a facial muscle to wield emotional power over humans

In a project that has all the makings of a Roald Dahl classic, scientists have hit on an answer to the mystery of how man's best friend got its puppy dog eyes.

The sad, imploring expression held such power over humans during 33,000 years of canine domestication that the preference for dogs that could pull off the look steered the evolution of their facial muscles, researchers have said.