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.
Puppies require human care, and it’s no surprise that we find them adorable and want to take care of them. After all, they have the same characteristics that prompt us to care for and protect members of our own species when they are young and vulnerable. A recent study by scientists at Arizona State University explores the benefits to young dogs of being cute by addressing the question, “At what age are puppies the most adorable to people?”
In the study, 51 participants were asked to rate the attractiveness of pictures of puppies ranging from newborn up to 7 months. Three breeds (Jack Russell Terrier, Cane Corso and White Shepherd) were studied using 13 pictures of each breed. All pictures showed the dogs’ heads close up and in the same basic posture. The Jack Russell Terrier was considered most attractive at 7.7 weeks old, the Cane Corso at 6.3 weeks and the White Shepherd at 8.3 weeks. Having optimal cuteness around the age that puppies are weaned and their mothers lessen parental care matches the hypothesis that puppies being their most adorable from the human perspective has an adaptive function. That function is to encourage adoption and care by humans just when the mother dogs are winding down their care of the puppies.
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This finding may help explain how it is that puppies evolved to receive human care so extensively. Unlike their wolf cousins who are cared for by parents for about two years, dogs stop receiving parental care about the time they are weaned at around 2 months of age. After this brief period with their mom, they are on their own unless people assume the care. Without additional help from people, over 80 percent of puppies do not survive their first year.
As puppies need us to take care of them, there is strong selection pressure for them to induce us to care for them. One way to maximize the chance of human care is to look their very cutest at just the age when they transition from being cared for by their mother to being cared for by people. The authors of the study write, “This attraction of humans to dog pups at that phase of life may have given early dogs, and may continue to give today’s free-living dogs, a competitive advantage by being adopted and cared for by humans as conspecific care decreases.”
Interestingly, in previous studies with other species such as chimpanzees, humans, rabbits, cats and dogs, only dogs showed a peak age of cuteness. With the other species, there were no age-related trends associated with ratings of how adorable the young were.
This research explores more than just the reactions by humans to the look of puppies at different ages. Our responses to puppies shed light on the evolution of domestic dogs and our relationship with them. As the researchers write, “Any possible adaptive explanation of this cross-species attraction must remain highly speculative, but the possibility that dogs and humans may have co-evolved so that dogs are most attractive to people just at the point where human intervention would have the most positive impact on pup survival may contribute to developing an understanding of the mechanisms of domestication.”