New discovery in dogs points to paradox in nature

Brain size in some dog breeds does not seem to correlate with their intelligence.

We often think that brain size (compared to body size) is directly proportional to intelligence, or the level of intelligence of a species. However, a new study has found that dogs with larger brains compared to their bodies are not necessarily smarter.

Toy dog ​​breeds like Chihuahuas have larger brain size ratios than other breeds. (Photo: Getty Images).

"In other species, brain size indicates higher cognitive abilities. But here we see the opposite," said Dr Ana Balcarcel, an evolutionary biologist at the Institute of Evolutionary Sciences of Montpellier, France.

The study compared the ratio of dog brain size to body size by measuring 1,682 adult dog skulls from 172 different breeds. The data was recorded at the Natural History Museum of Bern, Switzerland.

From there, the researchers calculated the dogs ' "relative intracranial volume ," or simply the size of their brains compared to their body size.

The results showed that intelligent dog breeds, such as Siberian Huskies, which were originally bred to perform complex skills to assist humans, had the smallest brains relative to body size.

Meanwhile, dog breeds classified as "companion" dogs, such as Chihuahuas, which are kept primarily as pets, have the largest relative brain size.

Dr. Balcarcel also said that previous studies have mostly shown that large brain size correlates with longevity and survival rate, affecting decision-making ability and the ability to process information at a high level.

Viewed from this perspective, the study's findings actually point to a paradox in nature.

Working dog breeds like Huskies have small brains (Photo: Getty Images).

' The key difference here is that dogs do not live in the wild ,' explains Dr. Balcarcel. 'So they have evolved through a process of directed selection by humans.'

Research into brain shape in dogs also sheds some surprising light on their evolution.

Accordingly, the brains of domesticated dogs are about 20% smaller than those of wild gray wolves (Canis lupus) relative to body size. But compared to wild gray wolves, domesticated dogs are more specialized in complex social skills that cooperate with humans. For example, they can follow human gaze and interpret hand gestures with ease.

The study also found that dog breeds with relatively large brain sizes — mainly toy breeds such as Chihuahuas, Pomeranians, and Yorkshire Terriers — tended to exhibit higher levels of fear, aggression, separation anxiety, and attention-seeking behavior.

These breeds were bred primarily to be companions to humans, creating affectionate and attentive traits that were favorable for breeding and passing on through artificial selection.

Still, Dr. Balcarcel cautions dog owners that domestic dogs have been bred over centuries to have different cognitive abilities.

So no matter what breed your dog is, or what his brain characteristics are, he is still specialized in his own way.