Popular wisdom has it that cats are smarter than dogs.
If you’re a cat person.
The primary evidence cat people present is feline independence. It’s not that they can’t be trained, it’s that they don’t want to be trained is the prevailing logic. They’re so smart, in fact, they domesticated us, not the other way around, or so goes the old joke.
Dog people, on the other hand, believe trainability is the actual measure of intelligence. Cats are not smart because they’re aloof, they’re aloof because they’re not smart.
Late last year, however, science may have finally come up with a compelling objective measure in the great cats versus dog’s debate. In a study led by Suzana Herculano-Houzel, a neuroscientist at Vanderbilt University, researchers counted the number of neurons in the cerebral cortex of lions, brown bears, cats, dogs, ferrets, raccoons, hyenas, and mongooses. The cortex is the area of the brain responsible for cognition, memory, planning, thinking ahead and reasoning.
"Neurons are the basic information processing units of brains, so the more the neurons that a species has in its brain the larger the capabilities that species should have," Herculano-Houzel explained.
Empirically speaking, dogs average approximately 500 million neurons while cats have only 250 million. Conclusion: Dogs are twice as smart as cats.
Of course, as with most human endeavours, a lot depends on how you define intelligence and people tend to believe what they want to believe despite either the presence or absence of evidence, so perhaps the debate is not yet settled.
Nevertheless, another interesting outcome of the study was that brain size does not seem to matter. For example, racoons, with a brain size approximately the same as cats have about the same number of neurons as dogs, while bears with a brain the size of a dog’s has the same number of neurons as a cat.
The conclusion that dogs are smarter than cats is no huge revelation, the opinion of cat people notwithstanding. In fact, it is more of a confirmation of relative intelligence. We have long known through cognitive tests that among the super smart in the animal kingdom are primates (chimpanzees, orangutans, gorillas), cetaceans (dolphins, whales), corvids (ravens, crows), parrots and elephants. In the medium group, we’ve got pigs, dogs, octopi, rats, racoons, and possibly certain species of spiders and ants.
Sorry cat people, your feline friends just don’t make the grade. That does not make them unworthy of our love, however.
Cerebral cortex neuron counts back up the above ranking. While only mammals have a cerebral cortex, birds have an equivalent forebrain structure that in corvids and parrots are packed with primate-like numbers of neurons (around 6 billion) despite being tiny. Think about that the next time you want to denigrate somebody’s intelligence by calling them a birdbrain. This makes a lot of evolutionary sense. Birds need to minimize weight in order to fly, which is why their bones are hollow and presumably why their brains are small.
Cerebral cortex neuron counts also confirm our own special place in the animal kingdom. When it comes to neuronal density, the human cortex is far and away the most packed at around 16 billion.
That is 32,000 times as many as a dog. While it is impossible to make a direct mathematical comparison—i.e., humans are 32,000 times smarter than dogs—the difference is mind-boggling.
Before we get too proud of ourselves, however, we may end up being too smart for our own good.