The Bigger the Brain, the Smarter the Dog? Not Necessarily
The bigger the brain, the smarter the dog, right? Not necessarily! A new study looking at the brain size of different dog breeds relative to their skull sizes found that dogs with larger brains aren’t necessarily smarter (1).
The research examined the ratio of dogs’ brain sizes to their body sizes. Researchers measured the skull sizes of 1,682 dogs from 172 different breeds and calculated each dog’s brain size relative to their body size, which they referred to as a dog’s “relative endocranial volume.” These dogs were evaluated through various behavioral tests and scored on 14 different traits, including their trainability, aggression, and attention-seeking behaviors.
The study found that larger breeds, such as working dogs, tend to have more complex abilities, like assisting humans with tasks such as herding sheep, but their brain sizes were smaller relative to their body sizes. Smaller breeds, such as Chihuahuas, which were bred for domestic companionship, exhibited the largest relative brain sizes.
The team behind the study found these results somewhat surprising. “In the wild, the pattern of brain size evolution toward larger relative size has been associated with higher cognition,” says Ana Balcarcel, the study’s lead author and an evolutionary biologist at the Montpellier Institute of Evolutionary Sciences in France.
“Big dogs have smaller relative brain size, that is the size of the brain relative to body size (in this case mass),” Balcarcel adds. This ratio, she explains, is traditionally used to infer cognitive ability or the capacity to process information. “But in dogs, we see the opposite, that dogs with smaller relative brain size are known for certain cognitive abilities,” she explains. The scientists emphasize that brain size is just one factor contributing to our understanding of intelligence, and many other important aspects remain to be explored.
Balcarcel notes that dogs are bred for a wide range of sizes and skills, so noticing a pattern between their function — such as working dogs versus pet or companion dogs — and their relative brain sizes was somewhat surprising, given the significant variation in selective breeding.
Each dog has unique skills for which they were bred, she adds, making them special in their own way. Previous research has shown that working dogs may have better short-term memory or executive function, while other breed groups have their own specialized abilities.
Does this mean certain dog breeds are smarter than others? Not necessarily. “Smartness or intelligence is too complex a concept to explain simply through brain size, so no, we cannot say that from our results,” Balcarcel says.
Understanding a dog’s intelligence remains a complex challenge, and Balcarcel emphasizes that there is still much to learn. Next, the team plans to study the shape and structure of the canine brain, exploring whether specific brain areas differ in size among breeds and how these differences relate to their skills or specializations.
Reference
- Balcarcel, Ana M et al. “Breed function and behaviour correlate with endocranial volume in domestic dogs.” Biology letters vol. 20,11 (2024): 20240342. doi:10.1098/rsbl.2024.0342
