In each of the dogs' brains, despite varying in size, researchers found about 500 million neurons, more than double the 250 million found in the cat's brain.ĭogs Change Facial Expression When Humans Pay Attentionīased on the number of neurons found, they speculated that dogs have roughly the same intelligence as raccoons and lions, while domestic cats have comparable intelligence to bears.įor comparison, humans have by far the highest number of neurons in our cerebral cortexes-as many as 16 billion per person. Two brains were used to study dogs because the canines vary so greatly in size. To get an idea of how many neurons dogs and cats might typically have, the team used three brains-one from a cat, one from a golden retriever, and one from a mixed-breed small dog.
"The cortex is the part of the brain that gives complexity and flexibility," said Herculano-Houzel. While different parts of the brain process outside stimuli like sight and touch, the cerebral cortex puts these stimuli together to drive decision-making and problem-solving, among other functions. To make her results-yielding "brain soup," as she calls it, the research team used only a part of the brain called the cerebral cortex, the crinkly outer layer that sits on top of the brain's other pieces. "The more units you find in the brain, the more cognitively capable the animal is."
"Neurons are the basic information processing units," said Herculano-Houzel.
From there, she said, you end up with a number of suspended nuclei from neuron cells that allow the researchers to estimate the number of neurons present. "You take the brain and turn it into a soup," she said, matter-of-factly, as the first step to finding these neurons. To get as precise a measurement as possible, she starts by counting neurons, a special type of nerve cell found in the brain that transmits messages. For the past decade, the now Vanderbilt professor has been studying cognitive function in humans and animals. One of the study's authors is noted neurologist Suzana Herculano-Houzel.
A team of researchers from six different universities in the U.S., Brazil, Denmark, and South Africa contributed to the research. This finding was provisionally accepted for publication and will soon publish in the journal Frontiers in Neuroanatomy. One of our most contentious debates may now have an answer.ĭogs, it turns out, have about twice the number of neurons in their cerebral cortexes than what cats have, which suggests they could be about twice as intelligent.
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