Dog Breeds and Cognitive Traits: How Much Do Genes Explain?
Researchers show aspects of dog cognition are heritable.
Posted August 20, 2020 | Reviewed by Matt Huston
Thousands of years of selective breeding by humans has resulted in an extraordinary degree of diversity in domestic dogs. Currently, more than 400 dog breeds are recognized internationally, running the gamut from 150-pound guard dogs to 5-pound "toy" companions.
Recently, genomic sequencing studies have begun to elucidate the genes behind dogs’ varied sizes and shapes. But much less is known about genetic differences in the ways dogs think and behave. Now, in a pair of new studies, researchers combine citizen science and big genomic data to examine whether there are genetically based breed differences in cognitive and behavioral traits.
Sit. Stay. Think.
The researchers collected cognitive data through Dognition.com, a citizen science website developed by Duke University dog researcher Brian Hare. The site guides owners through a series of experiments reflecting different aspects of cognition that they can complete at home with their dogs.
For instance, in a task that assesses inhibitory control, the dog owner puts a treat on the floor in front of the dog and then tells the dog not to take it, measuring how long the dog waits before giving in and eating the treat. Another task, which measures communication skills, involves the owner placing two treats on the ground and gesturing towards one of them. The owner then records if their pet approaches the indicated treat.
The result, according to Gitanjali Gnanadesikan, a graduate student at the University of Arizona and lead author of the new studies, is a massive database of thousands of pet dogs from around the world that have all done the exact same tasks.
“If I were trying to individually collect all that data myself, it would take years, probably decades,” she says.
In the first study, Gnanadesikan and colleagues integrated data from Dognition.com with publicly available information on the genomes of dog breeds, producing a dataset with 1,508 dogs across 36 breeds.
The researchers were interested in the extent to which a dog’s breed was predictive of cognitive or behavioral traits; in other words, the heritability of those traits. Heritability is the proportion of the total variation that you observe that can be attributed to genetic factors.
They identified genetic contributions in four cognitive domains. At the top was inhibitory control, which was estimated to be 70% heritable, and then communication, 50% heritable. They also found memory and physical reasoning to each be about 20% heritable.
What makes this especially interesting is that the two most highly heritable traits, inhibitory control and communication, are hypothesized to have been altered by domestication.
One theory about dog domestication is that dogs may have been selected for their ability to inhibit certain responses and behaviors. Early in domestication, those animals that were less reactive and aggressive and more accepting of human touch may have had an advantage.
When it comes to communication, it seems plausible that, whether intentionally or not, dogs may have been selected for the ability to pay more attention to human communication. Many studies show that dogs can communicate cooperatively and flexibly with humans in ways that wolves cannot.
The Story in the Genes
Next, Gnanadesikan and her colleagues conducted a genome-wide association study to identify specific genetic variations associated with breed differences in the traits found to be heritable in the first study (inhibitory control, communication, memory, and physical reasoning). Once again combining data from Dognition.com with published genome data, this time their dataset consisted of 1,654 dogs representing 49 breeds.
Overall, the researchers found that there were many genes, each with a small effect, that contribute to dogs’ cognitive traits. The researchers identified 188 genes implicated in breed differences in cognition. The genes tended to be highly expressed in brain tissue and involved in the functioning of the nervous system.
While this study shows that many genes contribute to cognitive traits, other features in dogs have been found to be more genetically straightforward. Gnanadesikan says that much of the diversity in dog shape and size has come about through intentional selective breeding, with efforts over the last hundred years especially focused on looks.
“We see that features like body weight and height are mostly governed by a single gene that has different versions in small and large dogs,” says Gnanadesikan. “That single gene explains a huge percentage of the variation in size between breeds.”
The story for behavior and cognition is more complicated.
“On the one hand, selection for these traits probably started much sooner than selection for morphological traits, likely hundreds to thousands of years ago, when dogs might have been selected for traits like herding or guarding behavior,” she continues. “But these traits are harder to quantify and probably more polygenic.”
It’s also the case that cognitive traits are influenced by environment and training. Gnanadesikan emphasizes that environmental and experiential factors should not be overlooked and cautions against assumptions or stereotypes about different breeds.
“These studies absolutely do not show that genetics is all that matters and a given breed is going to behave in a certain way and there is nothing you can do about it,” she says. “Even the most heritable traits in our studies still have a significant portion of the variation that is not explained by genetics.”
What Makes a Good Boy (or Girl)?
One limitation of these studies is that the cognitive and genetic information did not come from the same dogs. Gnanadesikan says these initial studies provide a roadmap for places in the dog genome that researchers could look at in more detail in the future.
Additionally, Gnanadesikan is working with a service dog organization, Canine Companions for Independence (CCI), on similar questions of cognition and heritability. She is hoping that such research can help programs like CCI breed and train successful service dogs.
“With all these organizations, the list of people in need outnumbers the available dogs. At most, 50% of the dogs in the program end up graduating as assistance dogs,” Gnanadesikan says.
“The hope is that by understanding more about what makes a good service dog, both genetically and cognitively, we might be able to improve success rates. Perhaps we could better identify what behaviors are needed for a good service dog and how training and breeding could both play into that.”
As much as Gnanadesikan is interested in the genetic contributions to cognitive traits, she also emphasizes the contributions of environment and experience and how all these factors interact.
“We’ve finally come to the understanding that both nature and nurture matter, but it’s still not really clear for any given trait how these factors combine,” she says. “I want to understand how a genetic predisposition interacts with environmental variables and experiences to influence a trait, in other animals and ourselves.”
Gnanadesikan, G.E., Hare, B., Snyder-Mackler, N., and MacLean, E. L. (2020). Estimating the heritability of cognitive traits across dog breeds reveals highly heritable inhibitory control and communication factors. Animal Cognition 23: 953–964. Doi: 10.1007/s10071-020-01400-4.
Gnanadesikan, G.E., Hare, B., Snyder-Mackler, N., Call, J., Kaminski, J., Miklósi, A., and MacLean, E. L. (2020). Breed differences in dog cognition associated with brain-expressed genes and neurological functions. Integrative and Comparative Biology icaa112. Doi: 10.1093/icb/icaa112.