There's a Reason People Love Puppy-Dog Eyes

An anatomic feature shared by humans and dogs has helped domesticated canines develop an ability to mimic and respond to human emotions, according to a study from the Rangos School of Health Sciences at Duquesne University in Pittsburgh.

What to know:

• Dogs are unique among mammals because of their ability to have a reciprocal bond with humans through mutual gaze, something not observed between humans and other domesticated mammals, such as horses or cats.

• Like humans, dogs have facial muscles that form facial expressions. The muscles are dominated by "fast-twitch" myosin fibers known as mimetic muscles.

• These muscles contract quickly but also fatigue quickly, which is why humans can form facial expressions rapidly but not hold them for long.

• Humans contributed to dogs' ability to form facial expressions by selectively breeding dogs on the basis of expressions that were similar to their own. Over hundreds of years, dog muscles appear to have evolved to become faster at mimicking.

• Dogs are closely related to wolves, but dogs have an additional mimetic muscle that is absent in wolves and that contributes to the "puppy-dog eye" expression.

This is a summary of the article, "Study Reveals the Science Behind Those Irresistible Puppy-Dog Eyes," published by Experimental Biology on April 5, 2022. The full article can be found on psych.org.