It’s not unusual to hear a dog owner praise their pet for being a clever boy.
But if you want a well-adjusted canine that will follow your instructions, you may want to consider getting one with a small brain.
In general, animals with more impressive cognitive abilities tend to have brains that are relatively large compared with their bodies.
A new study suggests that dogs may break this rule. It found that working breeds such as rottweilers and dobermans scored highest for “trainability” and for short-term memory, features the researchers argue are “suggestive of enhanced cognition”. These breeds led the pack despite having the smallest brains in proportion to overall size.
Border collies are regarded as one of the cleverest breeds, but have only medium-sized brains
ALAMY
Those with the largest brains were the toy breeds. Bred to be compact companions rather than for completing complex tasks, they include pomeranians and chihuahuas. While there was no sign of a link between big brains and higher cognitive ability, the dogs were more likely to exhibit fear and aggression, attention-seeking behaviours and separation anxiety.
The study measured the “relative endocranial volume” (REV) — size of brain in relation to overall size of dog — of 172 breeds. In general, the smaller the dog, the higher its REV.
Herding breeds such as collies are often over-represented when researchers look for very clever dogs that can remember the names of dozens of toys. However, their REV scores were only slightly higher than the working breeds, and scored far below the toy breeds. The same was true for labradors, German shepherds and golden retrievers.
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“Just because a collie has a medium, middle-of-the-line brain size, it does not mean that they are not capable,” said Dr Ana Balcarcel of Montpellier University, who led the research.
She said the results highlight how selective breeding by humans has made the dog an oddity in the animal kingdom. Among mammals, for instance, proportionately large brains are often associated with social species.
Humans, for example, have very large brains that are “expensive” to maintain, in terms of requiring lots of energy. The so-called “social brain” hypothesis argues that we need them to build and navigate our complex societies.
Dogs are also a social species. However, the research found that there was no link between REV and how well a breed tended to co-operate with humans, which was used as a marker of “social cognition”.
Domestication of dogs is known to have led to their brains shrinking
MICA RINGO/GETTY IMAGES
Balcarcel said: “This would have been evidence to support the idea that social cognition increases brain size, but we don’t see it. It is because dogs are not representative of nature. This is my biggest takeaway from the study: they are anomalous because they have been so strongly, artificially selected for these weird proportions and different body sizes.”
Domestication of dogs, thought to have begun between 14,000 and 29,000 years ago, is known to have led to their brains shrinking — on average they are 20 per cent smaller than those of wolves from which they descended, after accounting for body size differences.
For dog owners, Balcarcel said the findings should underscore the role of breeding. “To understand your pet, it’s helpful to understand the selection that has been applied to its lineage,” she said. “We tested trainability, aggressive behaviour and separation anxiety — and the smaller your dog, the higher problematic behaviours. So your dog might be aggressive and have separation anxiety not because it’s a terrible, terrible pet, but because it’s been bred this way.”
The results have been published in Biology Letters, a journal published by the Royal Society.
