English setter puppies sit next to a young Scottish girl.
For National Puppy Day, we created an adorable photo gallery that shows puppies playing with each other, posing for the camera, and interacting with people around them. But what is it that makes them seem so cute as they melt our hearts?
The leading theory, known as the "baby schema" effect, says a release of the chemicals dopamine and oxytocin is triggered in the brain when humans look at puppies. The same chemicals are released when we look at babies, and similar chemicals are released when we fall in love.
This chemical release is triggered by visual cues in baby mammals, including a large head relative to body size, big eyes, rounded body shape, and soft body surfaces. Since human babies are helpless for many months, our biological response to them makes us want to care for and protect them, so it's an evolutionary advantage for our species.
But it also means we feel happy when we see puppies, whether in real life or in a photo gallery celebrating the furry, wiggly bundles of cuteness.
National Puppy Day, created by author Colleen Paige in 2006, aims to highlight the abuse of puppy mills and promote the adoption of puppies. So if you're thinking of bringing one into your home for your own dose of regular happiness, consider this gallery to be a gentle nudge in that direction.