Dog or cat: with equal affection, who wins in intelligence? To the eternal debate is added, now, one more study: this time, on the actual number of neurons in the cortex, the largest and most external structure of the brain, assigned to the most complex cognitive functions.

Suzana Herculano-Houzel, psychologist and biologist at Vanderbilt University (Tennessee) has developed a method to quantify the number of cortical neurons in the brains of 8 species of domestic and wild carnivores, including dogs and cats. He thus discovered that Fido wins hands-on, indeed, legs-low this challenge with 530 million neurons in the cortex, against the 250 million of the cats (so to speak: a human brain boasts about 16 billion cortical neurons).

Image The brains of six carnivores of the eight considered in the study, in an illustration. | Suzana Herculano-Houzel / Vanderbilt

In other animals. A significant difference, the one found, also because when the analyzes were passed to the other carnivores, the number of nerve cells in the cortex did not appear to be proportionate to the size of the brain. For example, a golden retriever's brain contains far more cortical neurons than a brown bear's, although the latter is three times larger.

Energy saving. In large carnivores, the ratio of cortical neurons to brain size is actually lower: hunting requires a lot of energy, and supply rates are never certain. The brain requires continuous energy, and asks for it in relation to the number of neurons it has to feed: this is why the rhythms of hunting and the resources it gives limit the total number of neurons available.

The only exception to this rule is curiously represented by the raccoon, which has a brain similar in size to that of the cat, but with a number of neurons comparable to that of dogs.

The intelligence of dogs. Although all masters swear by the high intelligence of their four-legged, as a species the dog (Canis lupus) cannot compete with chimpanzees, crows, or dolphins. But, unlike these animals, it has a very deep empathy with the human being, so much so that he can understand in advance what the owner's intentions are.

His intelligence sometimes has characteristics that seem almost human; for example it is able to recognize faces after having seen their fixed image, or to classify in complex categories (landscapes or dogs) complex color photographs.

Even among dogs, however, there is a "ranking" of intelligence, made by psychologist Stanley Coren in the 1994 book The Intelligence of Dogs.

Top ten. Relying on the responses of the dog trainers associated with the American and the Canadian Kennel Club, Coren has compiled a list of the most intelligent breeds. Among the first were some shepherd dogs, such as the border collie or the German shepherd, as well as companion dogs, such as the tramp or the dwarf epainul. Not surprisingly, the ranking has been challenged by fans of other dog breeds.

The intelligence of cats. Unlike experiments done to test dogs, those with cats have given contradictory results. On the other hand, as Stephen Budiansky denounces in the book The character of the cat (Raffaello Cortina Editore), judging a solitary predator as the cat is rather complex: «It makes no sense to consider it more stupid than a dog for the simple fact that cats are not able to learn to report an object, "says Budiansky.

But a cat is ready to learn if it is given a reward: the more immediate it is, the better. It has been shown that they are excellent judges of the time, and are able to generalize the "discrimination of objects", for example one white and one black. "The true intelligence of the cat", concludes Stefano Moriggi, historian and philosopher of science, "is that of remembering, in its nature, independence and wild life", which makes it return to being a predator as soon as man disappears .