A new study by Oxford University shows that canines have larger brains than felines because they are a highly social species. While researchers were mapping the evolutionary history of the brain across more than 500 different mammals, they found that there is a link between the sociality of animals and the size of their brains relative to body size.
The brains of monkeys grew the most over time, followed by horses, dolphins, and dogs. The brains of solitary animals, like cats, grew much more slowly during the same period. The study suggests that social animals may have developed larger brains because group living is challenging--now I can see why humans have such large brains!