From the time they pop out as squirming little nuggets to months later when they're wreaking havoc on your baseboards, puppies are undeniably adorable. But as much as we like to believe that our adoration knows no age limit, a researcher has pinpointed the exact age we acknowledge optimal puppy cuteness.

Clive Wynne, professor of psychology and director of Arizona State University’s Canine Science Collaboratory, says it's about the time puppies are weaned. Canine attractiveness to humans peaks at roughly 8 weeks, the same time their mother stops feeding them and leaves them to fend for themselves.

Wynne was inspired in his research after spending time in the Bahamas and observing the many street dogs that live there. He says of the billion or so dogs in the world, 80 percent are feral, and those stray dogs rely on humans for their survival. Wynne was curious if there was some sort of link between a pup's weaning age — when they are the most vulnerable — and their level of attractiveness to humans.

Testing 'cute'

Images of a cane corso, Jack Russell terrier and a white shepherd were used in the study. Images of a cane corso, Jack Russell terrier and a white shepherd were used in the study. (Photo: Clive Wynne et al.)

For the study, Wynne and his team used a series of photos of puppies of three different breeds taken at different ages. The breeds were very distinct: Jack Russell terriers, cane corsos and white shepherds. Fifty-one people were asked to rank the puppies' attractiveness in each photo.

Result suggested that the pups' attractiveness was lowest right at birth, then peaked just before 10 weeks, then gradually declined, before leveling off.

Cute perception varied a bit among breeds. Cane corsos hit maximum attractiveness at 6.3 weeks of age, Jack Russell terriers at 7.7 weeks of age, and white shepherds at 8.3 weeks of age.

“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 in a statement.

Looking into our relationship

Wynne said the study, which was published in the journal Anthrozoos, also adds insight into the human-canine relationship, the oldest and most long-lasting of human-animal relationships. Many credit the link to a dog's intelligence, but Wynne sees something else.

“I think that the intelligence of dogs is not the fundamental issue,” he said. “It’s this tremendous capacity to form intimate, strong, affectionate bonds. And that starts at maybe eight weeks of life, when they’re so compelling to us.”

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.