The size of the brain in some dog breeds does not seem to correlate with their intelligence level.
We often believe that brain size (relative to body size) is directly proportional to the intelligence of a species. However, a new study has found that dogs with larger brains relative to their bodies are not necessarily smarter.
Breeds like the Chihuahua have a larger brain size ratio compared to other breeds. (Photo: Getty Images).
Dr. Ana Balcarcel, an evolutionary biologist at the Montpellier Institute of Evolutionary Science in France, stated: “In other species, brain size indicates higher cognitive ability. But here, we see the opposite.”
The study compared the brain-to-body size ratio of dogs by measuring 1,682 skulls of adult dogs from 172 different breeds. The data were recorded at the Natural History Museum in Bern, Switzerland.
From this, researchers calculated the “relative cranial volume” of dogs, simply understood as their brain size compared to their body size.
The results showed that intelligent breeds, such as the Siberian Husky, which were bred to perform complex skills to assist humans, have the smallest brains relative to their body size.
In contrast, breeds classified as “companions,” like the Chihuahua, which are primarily kept as pets, have the relatively largest brain sizes.
Dr. Balcarcel also noted that previous studies mostly indicate that larger brain sizes correlate with longevity and survival rates, influencing decision-making and high-level information processing abilities.
Considering this perspective, the findings of the study reveal a true paradox in nature.
Working breeds like Huskies have smaller brain ratios. (Photo: Getty Images).
“The main difference here is that dogs do not live in a natural environment“, Dr. Balcarcel explained. “As a result, they have evolved through a selective process guided by humans.”
The study of brain shape in dogs also brings many surprises about their evolutionary process.
It was found that domesticated dogs have brains that are about 20% smaller than those of wild gray wolves (Canis lupus) relative to body size. However, compared to wild gray wolves, domesticated dogs are specialized in more complex social skills that facilitate cooperation with humans. For instance, they can easily follow human gaze and interpret hand gestures.
The study also discovered that breeds with relatively larger brain sizes—primarily companion breeds like the Chihuahua, Pomeranian, or Yorkshire Terrier—tend to exhibit higher levels of fear, aggression, separation anxiety, and attention-seeking behavior.
These breeds are primarily bred to be companions for humans, resulting in emotional traits and attentiveness that are favorable for breeding and passed down through artificial selection.
Nevertheless, Dr. Balcarcel cautioned dog owners that domestic dogs have been bred over centuries to exhibit different cognitive abilities.
Therefore, regardless of the breed of dog you have or the characteristics of its brain, they remain specialized in their own unique way.
