New research delves into the cornerstones of human-dog bonding.

Image credits Dae Jeung Kim.

Scientific pursuit can often feel remote, involving too many things leptons or quasars for us to truly connect. Every now and again, however, members of academia ask and then try to answer questions that speak to our core — for example, exactly when in their lifetimes do dogs reach maximum cuteness? Clive Wynne, professor of psychology and director of Arizona State University’s Canine Science Collaboratory, says it’s around the time they get weaned.

Someone else’s problem now

Wynne and his colleagues write that about 80% of the world’s billion-strong population of dogs comprises of feral animals. Wynne himself has had ample opportunity to observe these feral dogs and how they interact with humans — for example, by watching street dogs in the Bahamas. Despite the apparent independence, human intervention is crucial for the survival of feral or street dogs, the team writes.

The next question is, of course, what would motivate people to intervene on behalf of these animals. One of the factors that seemed promising to the team was ‘cuteness’. So they set out to see if there is indeed a connection between pups’ weaning age (the most vulnerable period during a dog’s life) and their attractiveness to humans.

The study involved pictures of puppies of three races (Jack Russell terriers, Cane Corsos, and white shepherds) taken at different ages. Fifty-one participants were asked to rank the photographs based on their attractiveness levels. The results suggest that pups’ attractiveness was lowest at birth, reached peak-cuteness at roughly 10 weeks of age, then gradually declined and leveled off. Per-race rankings found that Cane Corso hit maximum cuteness at 6.3 weeks of age, Jack Russell terriers at 7.7 weeks of age, and white shepherds at 8.3 weeks of age. Caution to the wise, though: fifty-one participants is quite a limited sample size.

“Around seven or eight weeks of age, just as their mother is getting sick of them and is going to kick them out of the den and they’re going to have to make their own way in life, at that age, that is exactly when they are most attractive to human beings,” Wynne said.

He adds that the findings offer some nuance to the origin and relationships between humans and dogs. Being the oldest human-animal relationship we’ve formed, this relationship is often touted on its practical merits: we’ve befriended dogs because they’re smart and they help around the cave. But Wynne says the results suggest dogs’ usefulness and intelligence isn’t the only — or, even, the main — chip they base their survival on.

“I think that the intelligence of dogs is not the fundamental issue,” he explains. “It does seem to me that the dog has something rather special, […] a very open-ended social program. That they are ready and willing to make friends with anybody.”

Wynne explains that while other animals, most notably cats and birds, have shown the ability to form especially strong bonds with humans, dogs take this to the extreme. He adds that the eight-week maximum cuteness point has biological and evolutional significance. The fact that pups are the most attractive to us during weaning — when they’re at their most vulnerable — suggests that dogs have evolved specifically to rely on human care, the team adds.

The findings are also reinforced by previous research into human-dog dynamics and human-wolf relationships. Such research revealed that even hand-reared wolves are less willing and comfortable engaging humans compared to domestic dogs. In other words, man’s best friend likely evolved their gregarious nature specifically to cozy up to us humans. Not that I’m complaining.

“For them, it’s the absolute bedrock of their existence. […] being able to connect with us, to find an emotional hook with us is what actually makes their lives possible,” Wynne says.

The eight-week point is just the point where the hook is biggest, the ability of the animal to grab our interest is strongest. But, having grabbed our interest, we continue to love them all their lives.”

The team plans to follow up on their research using videos of puppies at different ages instead of still photographs to determine if there are other factors to pups’ behavior (such as movement) that attracts people. Another area they want to further explore is how mother dogs perceive their pups’ cuteness over time — although they admit that last one will be difficult to perform.

The paper “Dog Pups’ Attractiveness to Humans Peaks at Weaning Age” has been published in the journal Anthrozoös.