In the animal kingdom, having a big brain is usually linked with being smarter.
But a new study by scientists in France shows this is not actually true when it comes to domestic dogs.
Researchers from the University of Montpellier analysed the brains of more than 170 dog breeds, comparing brain size with body size to measure how ‘big’ or ‘small’ each breed’s brain is.
They found that breeds with smaller brains respond best to training and have good short-term memory – two traits considered ‘clever’ in dogs.
Meanwhile, breeds with bigger brains scored higher for fear, aggression, attention-seeking behaviours and separation anxiety – traits linked with dimwittedness.
So, if you’ve got a big dog such as a Retriever, Rottweiler or Siberian Husky, they’re likely to have a smaller brain (when the brain:body ratio is applied but higher brainpower.
But if you have a smaller ‘fashionable’ dog that you can fit in your bag, they’re likely to have a larger brain but lower brainpower.
While the new findings may seem counterintuitive, the scientists explain that excessive breeding by humans has distorted the natural layout of canine brains.
if you’ve got a big dog such as a Retriever, Rottweiler (pictured) or Siberian Husky, they’re likely to have a smaller brain but higher brainpower.
Generally in the animal kingdom, large brains are seen as a sign of more advanced cognitive ability, but dogs seem to break this rule
The new study was led by Ana Balcarcel, a biologist and paleontologist at University of Montpellier, and published in Biology Letters.
‘Dogs exhibit multiple personalities, functions, and cognitive abilities that can surpass those of non-human primates,’ Balcarcel and colleagues say in their paper.
‘Our results show that complex skills and cooperative behaviour – a hallmark of social cognition – do not predict larger [brain size] in dogs.’
Toy dogs have larger brains (relative to body size), while working dogs have smaller brains relative to body size
Smaller ‘toy’ breeds, like Pomeranians and Chihuahuas (pictured), had the largest relative brain size, the team say. This is linked with more dim-witted traits – namely, fear, aggression, attention-seeking and separation anxiety
The researchers measured the braincases of 1,682 adult dog skulls – 172 different breeds in all.
They compiled data for ‘relative endocranial volume’ (REV), which is simply the size of the brain in relation to the overall body size.
The researchers explain: ‘REV increases with fear and aggression, attention-seeking and separation anxiety and decreases with trainability.’
It’s possible that the brains of bigger ‘working’ dogs have been reorganised into a more compact space, leading to their reported enhanced cognition, according to the researchers.
Generally in the animal kingdom, large brains are seen as a sign of more advanced cognitive ability.
Bigger ‘working’ breeds – such as retrievers (pictured) – had the smallest relative brain size, making them one of the most intelligent dog breeds
However, the findings show that dogs seem to break this rule.
The researchers say: ‘This hypothesis is contradicted by domesticated populations, which despite having smaller brains relative to their wild counterparts can demonstrate enhanced cognitive capabilities.’
Dogs are an outlier in this regard, likely because they’ve been intensively bred by humans over centuries, dramatically distorting their physical attributes.
The concept of ‘breed’ is not a natural one – rather, it was created by humans when we started to intensively breed canines in about the late 1800s.
Since then, dogs have been selectively bred to accentuate harmful features to create these so-called breeds to distinguish them from each other and fuel the dog-buying industry.
Overall, domestic dogs possess brain sizes that are, on average, 20 per cent smaller than those of their closest living wild relative, the grey wolf (Canis lupus).
Whether it’s foraging for food, avoiding predators or finding mates, domestic dogs have to deal with fewer cognitive demands compared with wild dogs.
Due to this reduction in the need for brain power, domestic dogs’ brains have gradually shrunk, the theory goes.
The researchers admit that personalities, skills and cognitive abilities can ‘vary within breeds and between individuals’.
