Humans haven’t just changed what dogs look like – we’ve altered the very structure of their brains

According to a study of 33 breeds of dogs, the role for which a dog was bred is reflected in their brain structure.

There are hundreds of dog breeds around the world due to centuries of selective breeding by humans from the teensy chihuahua to the massive Saint Bernard. With such an extensive range of canine sizes and temperaments, it’s not surprising that, in due course, humans have reshaped their brains as well as their bodies.

The new study performed MRI scans on 33 breeds and revealed how a dog was bred is reflected in their brain structure. For example, dogs bred to be small like the Lhasa apso have round heads with correspondingly round brains that occupy most of their skull. Larger breeds like a golden retriever with its long, narrow head have a more elongated brain that doesn’t fill all of the skull space.

Study leader Erin E. Hecht, an evolutionary neuroscientist at Harvard University, said, “The biggest wow moment for me was just looking at the scans. It’s really cool in science where you have a result where you don’t have to do any fancy statistics to be able to tell there’s something going on.”

This new look inside the mind of dogs offers a deeper understanding of how breeds are hardwired, which in line helps potential dog owners choose the right breed for their home, adds Hecht, whose study was published this week in the journal Neurosci.

Dogs On The Brain

For their study, Hecht and her colleagues recruited 62 individual pet dogs in American homes, covering breeds such as beagles, Yorkshire terriers, Doberman pinschers, boxers, and more. After observing the differences in brain size and shape, the team then further studied differences within the brain, observing how certain regions varied across breeds with certain behavioral traits.

For example, bulldogs which were originally bred to fight captive bulls but later raised to be loving family pets put them in both the “sport fighting” and “explicit companionship” categories. The study team referred to the American Kennel Club website for data on the breeds’ original roles.

The scientists subsequently mapped out six brain networks that could be distinguished by a dog’s behavior such as scent hunting or companionship. For instance, the prefrontal cortex part of the brain has one area associated with group size and social interaction which was found to have the same variation among dogs bred for herding, police, military, war work, vermin control, bird flushing and retrieving, and sport fighting.

This makes sense because all these breeds serve roles that are “cognitively complex and demanding, so they might require greater support from the prefrontal cortex,” according to Hecht.

Daniel Horschler, a PhD student in at the University of Arizona who studies brain anatomy in dogs and wasn’t involved in the research, praised the study’s approach by saying, “They didn’t try to divide the brain into regions themselves, which is I think a really good approach because we don’t yet know a lot about how dogs’ brains are organised”.

It was smart, he observed, that the team noted areas in which dogs’ brains tended to change in the same ways and then related those changes to breed-specific traits.

He adds, “It’s really exciting. Dogs are such a great model for this sort of thing and no one has really explored this before.”

Science’s Best Friend

Horschler remarks that though domestic dogs were once dissed by scientists as “a fake animal,” that were not worthy of scientific inquiry, they’ve now emerged as a more common study subject especially as part of the study of emotion and cognition. For example, 20,000 years of cohabitation has made pet dogs finetuned interpreters of human emotion, possibly more so than any other species.

Study author Hecht and colleagues also carried out a statistical analysis that demonstrated that the brain variations occurred more recently in the dog family tree, rather than deep in the past, signifying that “dog brain evolution has happened quickly,” Hecht says.

She notes, “It brings home how humans alter the world around them. It’s kind of profound that our brains are changing other brains on the planet.”

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