But it's not just size that matters. Dolphins also have a very complex neocortex, the part of the brain responsible for problem-solving, self-awareness, and variety of other traits we associate with human intelligence. And researchers have found gangly neurons called Von Economo neurons, which in humans and apes have been linked to emotions, social cognition, and even theory of mind—the ability to sense what others are thinking. Overall, said Marino, "dolphin brains stack up quite well to human brains."