Researchers at Vanderbilt University decided to find out how intelligent various animals are. To rightly compare brain power in species, it isn't enough to weigh brain tissue. You must take into account the brain relative to the organism's size. But this may fall short of evaluating actual intelligence. Neuroscientist Suzana Herculano-Houzel said, "I believe the absolute number of neurons an animal has determined the richness of their internal mental state and their ability to predict what is about to happen in their environment based on past experience." She and her colleagues found that meat eaters have about the same number of neurons as plant eaters. That means plant eaters need as much brain power to escape from predators as meat eaters need to catch them. How do cats and dogs measure up? Previous findings had cats ahead at 300 million neurons to dogs roughly 160 million. In this latest study, however, dogs were on top, with 530 million neurons to cats 250 million. Just for comparison, humans have around 16 billion such neurons. Even so, dogs were way above other meat eaters in the brain power department. Having a bigger brain has a downside, researchers have found. "Meat eating is largely considered a problem-solver in terms of energy," Herculano-Houzel said, "but in retrospect, it is clear that meat eating animals must impose a delicate balance between how much brain and body a species can afford." This may be why you often see large predators like lions and bears dozing.