In 2018, Hannah Salomons began a research journey that would span five years, several cities and more than 100 puppies training to be service animals.
A project that began in her first year as a Ph.D. student evolved into one of the most detailed longitudinal studies ever conducted on puppy cognition.
The goal? To understand how puppies develop thinking skills such as memory, impulse control, and the ability to interpret human gestures. She also is looking to uncover clues about how these skills evolved, and whether early cognitive traits can predict future behavior.
"I've always been fascinated by how animals think and learn," Salomons said. "When I arrived at Duke, I joined Brian Hare's Canine Cognition Lab because he was doing exactly the kind of research I was passionate about - especially around social communication and cooperation in animals."
"It was an incredible opportunity to be part of a long-term project from the ground up," she says.
The study's findings were recently published in Animal Behaviour. The team partnered with Canine Companions , a national service dog organization, along with several other groups, including Ears, Eyes, Nose and Paws and Guiding Eyes for the Blind .
The study's scope was ambitious: The pups (all labs and goldens or mixes of the breeds) were tested every two weeks from eight to 20 weeks of age. Researchers designed a battery of cognitive tasks to assess skills such as finding kibble in hidden locations.
One key question was whether these abilities develop together as part of a general intelligence factor, or whether they emerge independently.
"There hasn't really been a study of this size at this fine scale of detail done on puppy cognitive development before. It was a big undertaking," said Salomons.
The study was funded by the Office of Naval Research, the National Institutes of Health and the Canine Health Foundation. Salomons said each funder was interested in understanding various aspects of cognitive development.
Three Key Discoveries
The first major finding is that while most cognitive skills in puppies develop surprisingly early, they develop independently from one another, emerging at different times across this window of rapid development from eight to 20 weeks.
By 16 weeks, nine out of the 10 cognitive skills tested had already developed, Salomons said. "That tracks with what we see in neuroscience - puppies' brains are rapidly growing during this same period." Yet, the skills emerge at markedly different time points, indicating that they are separate forms of intelligence, rather than just one. This suggests that "there's no such thing as a dog who is simply 'smart' or 'dumb' - dogs, like humans, can have strengths and weaknesses in different areas," she said.
"What's fascinating is that the skills to communicate with humans show up in dog puppies but not in wolf puppies at this young age."
Hannah Salomons
Second, puppies appear biologically primed for cooperative communication. Skills such as understanding simple human gestures emerged early, alongside basic skills like working memory.
"What's fascinating is that the skills to communicate with humans show up in dog puppies but not in wolf puppies at this young age," Salomons said.
This suggests that domesticated dogs evolved specific cognitive traits that support communication with humans.
Third, the study revealed that extreme levels of socialization don't necessarily enhance cognitive development. Puppies raised on Duke's campus were exposed to hundreds of people and events - far more than typical family dogs. Yet their cognitive development was like that of puppies raised in home environments. This suggests there's a biological blueprint guiding how and when these skills emerge.
Evolutionary Insights and Practical Applications
From an evolutionary biology perspective, the study sheds light on how cognition may have evolved in both dogs and humans.
"There's a hypothesis that humans and dogs share some similar selections for friendly temperaments and against aggression, which led to similar changes in their brains that made us both good at cooperative communication," said Salomons. "This study supports that idea, showing that dog cognition is developing in a similar way to human cognition."
In humans, understanding gestures and cooperation emerges early - even before language. Infants grasp concepts such as pointing very early. Finding that dogs show similar early development strengthens the idea that we share evolutionary pressures that shaped our cognition.
Beyond the theoretical, the future work has practical implications for service dog organizations. Many of the puppies are being retested as adults, and Salomons is now analyzing which early behaviors predict success in service roles.
"Right now, only about 50 percent of service dogs pass their final evaluations," Salomons said. "Training each dog costs tens of thousands of dollars. If we can identify early predictors of success, organizations can invest more efficiently and help each dog find the right path."
