How Smart Are Dogs Compared With Other Animals?

Measured by brain cells in the thinking part of the brain, a dog came out ahead of every other meat-eating mammal in a 2017 study, including a lion and a brown bear. And at one skill in particular, reading what a person means when they point, dogs beat chimpanzees.

Counting the cells that do the thinking

Intelligence is hard to measure across species, so some scientists look at a simpler number: how many neurons, or nerve cells, sit in the cerebral cortex, the brain’s outer layer.

In 2017, a team including neuroscientist Suzana Herculano-Houzel published the results of counting those cells in several carnivores in the journal Frontiers in Neuroanatomy. A golden retriever had the most of any animal they studied, at 627 million cortical neurons. A smaller dog of unknown breed had 429 million. A cat had 250 million.

National Geographic summed it up neatly: dogs have about twice as many cortical neurons as cats.

Bigger brains, fewer cells

The surprise was that a bigger brain did not always mean more neurons. The golden retriever beat the African lion, with 545 million, and the striped hyena, with 495 million. The brown bear had only 251 million, about the same as a cat, even though the cat’s cortex is about ten times smaller than the bear’s.

The raccoon was a standout. Its cat-sized brain held 438 million cortical neurons on average, a dog-like number. Based on the counts, the researchers suggested that dogs may be roughly as clever as raccoons and lions, and cats about as clever as bears.

For scale, National Geographic reported that humans have as many as 16 billion neurons in the cortex, and chimpanzees about six to seven billion. So a dog is not close to a chimp by this measure.

What the neuron count leaves out

The study had limits. It covered only carnivorous land mammals, and the dog and cat comparison rested on just three brains. Sarah Benson-Amram of the University of Wyoming, one of the researchers, told National Geographic that more research is needed before anyone can say how meaningful brain size is as a measure of intelligence.

A neuron count is a clue, not an IQ test. To see what dogs can actually do, scientists turn to behavior.

The border collie with more than a thousand names

One of the most famous tests involved Chaser, a border collie trained by psychologists John Pilley and Alliston Reid of Wofford College in South Carolina. Over three years, they taught her the names of 1,022 individual toys, one name at a time. Their results were published in the journal Behavioural Processes.

To check that she really knew the names, testers put random groups of 20 toys in another room and asked her to fetch them by name. In 838 separate tests, she never got fewer than 18 out of 20 right. She also learned category words such as “ball.”

Before Chaser, the top dog was Rico, a border collie studied at the Max Planck Institute in Leipzig, Germany, who knew about 200 words.

Better than chimps at one thing

Dogs really shine at reading people. Researchers in Duke University’s evolutionary anthropology department have found that dogs are better at picking up human signals such as pointing than chimpanzees and other primates. They describe dogs as unremarkable thinkers in many ways but with an unusual ability to read what humans intend to communicate.

A 2012 study from the Max Planck Institute for Evolutionary Anthropology in Germany, published in PLoS ONE, put this to the test with 20 chimpanzees and 32 dogs. Each animal had to fetch the object a person wanted, shown only by the person pointing at it. The dogs did well. The chimps failed to identify the object the person meant.

So how smart is a dog?

The honest answer is that it depends on what is being measured. Chimpanzees have far more cortical neurons than dogs. But among the carnivores in the 2017 study, a dog carried the most neurons in the cortex, and in reading human pointing, dogs beat the chimpanzees tested.

Dogs may not be the brightest animals on Earth, but when it comes to following what a person is trying to tell them, they are hard to beat.