Quick Take
- What vets and trainers have long believed about spaying or neutering your dog turns out to be more complicated than previously thought, and the data from 47,000 dogs tells a different story. See the sterilization findings →
- Small dogs get a bad reputation, but the study reveals something specific about their behavior that most owners misread entirely. Discover small dog behavior →
- Mixed-breed dogs were expected to be the calmer, more balanced choice, but a 47,000-dog study disagrees. See mixed-breed results →
- Something shifted in how dogs behaved in the years 2021 to 2023, and researchers think the cause has less to do with the dogs than with us. Explore post-pandemic shifts →
Can a dog’s breed or size reveal hidden clues about its personality, health, or how it might behave as it grows older? A new study, tracking more than 47,000 pet dogs in the United States, offers the most comprehensive look yet at how biology and background combine to shape canine behavior and what it might mean for owners and animals alike.
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A Nationwide Project Lifts the Lid on Canine Character
The Dog Aging Project (DAP), a long-term research effort following tens of thousands of American pets, provided the foundation for this unprecedented study. Between 2020 and 2023, over 47,000 dog owners completed detailed surveys designed to capture their pets’ daily habits and moods. These responses fed into a shorter version of the well-regarded Canine Behavioral Assessment and Research Questionnaire, or C-BARQ, probing for patterns in fear, excitement, aggression, and trainability.
How long a dog takes to ask you for help says a lot about its intelligence
©iStock.com/SolStock
Researchers from Virginia Tech and the University of Washington led the effort, treating each dog’s profile not as an isolated story but as part of a much larger puzzle. “Most importantly, with these data, we’re excited to now have a starting point from which we can continue to follow changes in the behaviors of tens of thousands of dogs as they age, which will ultimately help us understand how behavior and health are linked,” explained Courtney Sexton, PhD, a postdoctoral researcher and the study’s co-lead.
Patterns Emerge: Breed, Size, and Changing Times
Once sorted and analyzed by principal component analysis, a way to find the most important threads among many different behaviors, four broad themes emerged: fear, attention and excitability, aggression, and trainability. These pillars provided a new map for exploring what makes dogs tick.
According to Sexton, the sheer size of the data set gives real-world weight to the statistical patterns. “When you have a data set this big, you really do have power in numbers. While we can’t understand all the factors, when we find statistical significance, there is likely something there worth thinking about in its real-world context.”
The study revealed differences not just by breed, sex, or size but even by year of enrollment. For example, dogs recruited during 2021–2023 showed a dip in trainability compared to those joining the project in 2020. Attention and excitability peaked slightly in 2022, while a notable decrease in reported aggression occurred only in 2023. These shifts weren’t massive or consistent year to year, suggesting other forces, such as post-pandemic life, may be at play.
Common family dog breeds can appear frequently in bite reports, but breed alone does not determine whether an individual dog will bite.
©Bigandt_Photography/ via Canva.com
What the Traits Reveal: Surprises in Small Packages
Mixed-breed dogs logged higher scores for fear, attention-seeking, and aggression than their purebred counterparts, but they didn’t differ in trainability. Size told its own story: smaller dogs (under 20 pounds) tended to be described as more fearful, more aggressive, and more demanding of attention, and rated lower in trainability than larger dogs.
The age of the dog mattered, too. Puppies, perhaps expectedly, called for more attention, and, while less fearful or aggressive than adults, were generally less trainable. Senior dogs, however, proved even more stubborn when it came to training.
Sex and reproductive status showed distinct outcomes. Female dogs were rated as more trainable than males. Interestingly, those that were spayed or neutered were generally assessed as more fearful and aggressive, and as less trainable, challenging the conventional notion that sterilizing a dog softens its temperament. Service and therapy dogs confirmed expectations by being less aggressive and more obedient than typical pets.
Geography had its influence, too. Dogs living in the Midwest appeared more attention-seeking than those from other regions. Yet, amidst the upheaval of the COVID-19 pandemic, behavioral profiles across all dogs stayed surprisingly stable.
What Owners Report, And What That Means
The researchers stressed caution when interpreting these findings. The study was built from owner-reported surveys, opening the door to bias and differing perceptions; factors such as training style, household stress, and owner experience went unmeasured. Notably, there were few intact (unspayed or unneutered) dogs in the pool, potentially skewing certain results. Above all, the findings suggest patterns and associations, not definitive proof that, say, a dog’s breed causes certain behaviors.
Five beautiful brindle dog breeds, each displaying their unique striped coats, sit together in a sunny outdoor setting.
©A-Z Animals
Despite these limitations, the breadth of the study marks a pivotal starting line for future research. Subtle shifts in behavior, like a dog growing more fearful or aggressive, could serve as early warning signs of declining health or cognitive change, enabling earlier interventions by owners and veterinarians. Differences by breed, age, size or sex could help tailor better training and welfare practices for a wide spectrum of dogs.
As Sexton observed, the smallest changes in averages, such as the slight rebound in trainability after the pandemic, hint that dogs, and maybe their people, are adapting. The story of dog behavior is far from finished, and studies like this one show just how much we all still have to learn from our closest animal companions.
