When I was a child there was a lot of excitement about dolphin brains and dolphin language. It didn't seem to go anywhere, but the cognitive sciences have been moving onwards.
In an era where almost every aspect of thought that seemed purely human has been found to be commonplace, it's time to reexamine the cetacean brain.
Scientific American features a brief review of the science. In short, there's no obvious neuro-anatomic reason to suppose that cetaceans should be less "clever" than humans. Indeed, sperm whales ought to be prodigies of thought.
So why do they need such massive brains? Those calorie sucking engines require an immense amount of food; sperm whale brains ought to be doing something to justify their costly upkeep.