There's a new twist on the perennial argument of who's smarter, cats or dogs. It has to do with their brains, specifically the number of neurons in their cerebral cortex:the "little gray cells" associated with thinking, planning, and complex behavior — all considered hallmarks of intelligence. The first study to actually count the number of cortical neurons in the brains of a number of carnivores, including cats and dogs, found that dogs have significantly more of them than cats. As for dogs and cats, the study found that dogs have about 530 million cortical neurons, while cats have about 250 million. (That's 16 billion in the human brain.)
The researchers analyzed the brains of one or two specimens of each of eight carnivoran species:ferret, mongoose, raccoon, cat, dog, hyena, lion and brown bear. They expected their measurements to confirm the intuitive hypothesis that the brains of carnivores should have more cortical neurons than the herbivores they prey on. However, that turned out not to be the case. The researchers determined that the ratio of neurons to brain size in small- and medium-sized carnivores was about the same as that of herbivores, suggesting that there is as much evolutionary pressure on the herbivores to develop the brain capacity to escape predators as there is on carnivores to to catch them.
For the largest carnivores, the ratio of neurons to brain regions is even lower. They found that a golden retriever's brain has more neurons than a hyena, lion or brown bear, although the larger predators have brains up to three times the size. The bear is an extreme example. The brain is 10 times larger than a cat's, but has about the same number of neurons.
