Nobody (that I know) would ever argue with the statement that puppies are incredibly adorable, because that is obvious. The sight of babies and puppies (and young members of other species, too) causes a reaction in people. Infantile characteristics seen in many young mammals—a proportionally large head, big and wide-spaced eyes, chubby cheeks, and small mouth and nose—make us feel caring and protective.
The young of species who require a lot of care are often perceived to be cute. That’s not just serendipity—that’s evolution. Individuals who are cute trigger caregiving behavior by altering the physiology of potential caregivers. In many mammals, including humans, the sight of attractive young results in the release of oxytocin, a hormone that has many effects, including feelings of love for and the inclination to tend to others.
via Whisker Therapy