The researchers wanted to find out if there was a connection between pups' weaning age -- when they are at their most vulnerable -- and their level of attractiveness to humans.
"There is indeed an optimal age of maximum cuteness, and that age does line up pretty closely with the age at which mothers wean their pups," said lead researcher Clive Wynne, Professor at Arizona State University in the US.
The researchers believe that the findings, published in Anthrozoos: A Multidisciplinary Journal of the Interactions of People and Animals, could provide insight into the depth and origin of the relationship between humans and dogs.
The study was carried out using a series of photographs of puppies at different ages, from the first weeks of life through young adulthood.
The participants were asked to rank the puppies' level of attractiveness in each photo. Three distinctive looking breeds were ranked -- Jack Russell terriers, cane corsos and white shepherds.
The results showed that the pups' attractiveness was lowest at birth and increased to a maximum before 10 weeks of age before declining and then levelling off.
"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.
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