Cat and dog owners can’t stop arguing over whose pet is smarter – is it cat or dog? But the study published in Frontiers in Neuroanatomy claims that it has an answer (1).
It found dogs to be “smarter” than cats. Or this is how the mainstream media reported it (2,3). If you are a cat lover you are probably annoyed by this claim – and rightly so.
· More neurons = smarter?
Researchers investigated the brains of the carnivore species: raccoon, cat, dog, raccoon, hyena, lion, brown bear, mongoose, and ferret. A cat and two dogs, one mixed breed and another golden retriever, they used in the study, died of natural causes.
Scientists counted how many neurons each species have in the cerebral cortex.
For those who do not know, the cerebral cortex is the outer portion of the brain, consisting of layers of nerve cells and the pathways that connect them. Neurons are nerve cells that transmit information through an electrochemical process.
Researchers found that a dog has 530 million but a cat has only 250 million. To put it into perspective, the average human has impressive 16 billion cortical neurons.
Although the brown bear has a large brain, its neuron count turned out similar to that of the cat.
Lions and hyenas also have fewer neurons for their size, not so different from their prey species, such as the blesbok and kudu. This is because having a large body size and maintaining a large number of neurons would require a lot of energy: these predators would be put at a disadvantage from the evolutionary point of view (4).
The brains of six carnivore species compared. Courtesy: Suzana Herculano-Houzel.
Measuring an animal intelligence is difficult. But Suzana Herculano-Houzel, a leading author of this study, believes that neuron count is the most effective to date way to measure animal intelligence (3).
Herculano-Houzel, who describes herself as “100 percent a dog person” was delighted to find that dogs have twice as many neurons as cats:
“Dogs have the biological capability of doing much more complex and flexible things with their lives than cats can. At the least, we now have some biology that people can factor into their discussions about who’s smarter, cats or dogs (4).”
Photo credit: Fedotov Anatoly
“This is complete nonsense”
Although mainstream media accepted the conclusions of the study uncritically (the headlines appeared even before the study was published!), some biologists and geneticists were not so impressed.
Jessica Perry Hekman, a veterinary geneticist at MIT and Harvard’s Broad Institute, said that we do not have enough evidence to claim that neuron number is strongly tied to the intelligence (5). After all, each species of animals have evolved different abilities and ways to adapt to their environments. If they are able to survive and thrive with a smaller number of neurons, these animals are obviously intelligent enough.
Evolutionary biologist Prof. Jerry Coyne did not see a reason to take this study seriously: “Sorry, but this is complete nonsense […]. The real way to see which animal is smarter is to devise some test that comports with your definition of animal intelligence, and then apply it to the species in which you’re interested. You also have to be sure that the animal can be trained to take a test—and we know about the training of cats versus dog (6).”
Herculano-Houzel had to admit to Huffington Post that she did not study the behavior therefore she cannot and did not make any claims about how intelligent these animals are (7).
Compared to dogs, raccoons have exceptional problem-solving skills yet their neuron count is the same as dogs (1). What’s more, the number of neurons also cannot explain why dogs perform worse than wolves in behavioral experiments.
Despite of having similar to dogs number of neurons, raccoons are better at problem-solving. Photo credit: Linda Davidson.
Besides, the size of the dog matters when comes to the number of neurons. The small breeds of dogs like Chihuahuas are expected to have significantly fewer neurons.
Veterinary geneticist Hekman suggests that an animal’s number of synapses, connections between neurons, might be a more accurate measure of intelligence (5). The experience in early life has profound effects on animal’s brain anatomy. Hekman says that rats raised in small cages developed more synapses when they were given toys and conditions that allowed those rats to play and explore, compared to other rats raised in empty cages.
To summarize all above, it seems like counting neurons may not be the best way to study animal intelligence.
But we are still left with a question: are dogs smarter than cats?
Coyle provides us with evidence to the contrary. He posted a video of the dog that can’t figure out how to turn the stick sideways. What would a cat do?
“A cat wouldn’t even pick up a damn stick to please somebody else.
Now, who’s smarter?”
Alvarenga, D. J. M., Lambert, K., Noctor, S. C., Pestana, F., Bertelsen, M. F., Manger, P., & 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. Frontiers in Neuroanatomy, 11, 118.
2. Mcrae M. (2017, 30 Kasım). When It Comes to Dog vs Cat Brains, It Looks Like We Have a Clear Winner. Science Alert.
3. Gibbens S. (2017, 30 Kasım). Are Dogs Smarter Than Cats? Science Has an Answer. National Geographic.
4. Salisbury D. (2017, 29 Kasım). Sorry, Grumpy Cat—Study finds dogs are brainier than cats. Vanderbilt University.
5. Bittel J. (2017, December 4). Which animals are smartest: Dogs, cats, or … raccoons?The Washington Post
6. Coyne J. (2017, 9 Aralık). Are dogs smarter than cats? Why Evolution is True
7. Hanson. H. (2017, 30 Kasım). Did A Viral Study ‘Prove’ Dogs Are Smarter Than Cats? Not Quite. Huffington Post