Correlation between brain size and intelligence isn’t straightforward. Humans are the most intelligent lifeform on the planet, yet our brain is smaller than that of an elephant or whale. Relative to body weight, humans still don’t have the largest brains, we have a similar relative brain size to mice!
Even comparing sizes of human brains to one another, intelligence and size don’t directly correlate. Albert Einstein had an ‘average’ sized brain for example.
A recent study looked at the cognitive data of over 7,000 dogs across 74 breeds with a range of brain weights and body sizes, to investigate this correlation.
What Makes a Brain ‘Smarter’?
If absolute size and relative size don’t equate to more intelligence, what makes humans special? What makes one person or one dog smarter than the next?
A more definitive measure of intelligence can be determined by the number of neurons in the brain and how dense they are packed. These factors make up an individual’s information processing capacity (IPC), of which humans come out on top 1.
As the brain size of a dog increases, the number of neurons also increases. One comparison found that a golden retriever (body weight of 32 kg) contained 627 million neurons, while an unknown breed (body weight of 7.45 kg) contained 429 million neurons 2.
How Can You Testing a Dog’s Intelligence?
The study in Animal Cognition collected data from Dognition, a website that gives users games to play with their dogs to determine how smart they are.
Dognition hosts 20 games that were created by scientists, trainers, and behavioral specialists. These games help determine the empathy, communication, cunning, memory and reasoning of your dog.
The results from these games are saved on the Dognition website and go towards creating an overall profile for your dog.
Games included tasks such as a pointing to food with an arm and then a foot and seeing how your dog responds. Or another example, which larger-brained dogs did particularly well in, was to forbid food and time how long it took for the dog to eat the food without any further interaction.
Did Large-Brained Dogs do Better in Tests?
The study hypothesised that dog’s with larger brains (and more neurons) would have greater intelligence.
By estimating average brain size using breed information and comparing this to the test results stored on the Dognition website, the study demonstrated correlation between brain size and performance for certain games 3.
Larger-brained breeds performed better in tests of short-term memory and self-control. However, the same correlation was not seen in all other tests of cognitive function.Larger-brained dog breeds perform better in tests of short-term memory and self-control. Click To Tweet
For example, larger-brained breeds exhibited greater self-control by waiting significantly longer to eat food that was forbidden by their owner, in the ‘cunning’ test.
In conclusion, a larger brain didn’t result in an all-round improvement of intelligence, but did demonstrate an improvement in certain areas.
How Big is Your Dog’s Brain?
Below is data from a 1979 study that compared the brain weights of dogs, cats and horses to their body weights. Below are the average weights for each of the dog breeds listed in that study.
|Breed||Avg. Brain Weight (g)||Avg. Body Weight (kg)|
|Toy Fox Terrier||52.3||3.4|
|Old English sheepdog||104.4||38.6|
Values from Bronson Study, 1979 4.
Does Your Dog Follow the Trend?
Do you consider your dog to be intelligent? Are they big or small, let us know in the comments below.
If you want to determine your dog’s intelligence using Dognition, they have plans starting at $29, see their website for more details.
Summary: The Effect of Breed Size on Intelligence
- Larger brain size means more neurons, which correlate to intelligence.
- Large dog breeds have on average a larger brain (by weight).
- Larger-brained dogs performed better in tests of memory and self-control.
- Not all areas of cognitive intelligence were improved by having a larger brain.
Graphics Provided by www.Vecteezy.com
- Dicke U, Roth G. Neuronal factors determining high intelligence. Philos Trans R Soc Lond, B, Biol Sci. 2016;371(1685):20150180. ↩
- Jardim-Messeder D, Lambert K, Noctor S, Pestana FM, de Castro Leal ME, Bertelsen MF, Herculano-Houzel S (2017) Dogs have the most neurons, though not the largest brain: trade-off between body mass and number of neurons in the cerebral cortex of large carnivoran species. Front Neuroanat 11:1–18 ↩
- Horschler DJ, Hare B, Call J, Kaminski J, Miklósi Á, Maclean EL. Absolute brain size predicts dog breed differences in executive function. Anim Cogn. 2019;22(2):187-198. ↩
- Bronson RT. Brain weight-body weight scaling in breeds of dogs and cats. Brain Behav Evol. 1979;16(3):227-36. ↩