A scientist from South Africa (Paul Manger from Johannesburg's University of the Witwatersrand) is basically saying that the Hitchhikers Guide to the Galaxy got it all wrong. Dolphins are stupid. Or more succinctly, they are as smart as a bag of hammers. In fact says he, Goldfish are smarter. It seems the size of the Dolphin's brains are due to an overabundance of glia, and well, an underabundance of neurons. The neurons do the thinking (so to speak), and the glia have the support roll, feeding, making connections, and most important in Dolphins, providing heat in cold environment. Here are a couple of links to check out. To the Dolphin's defence, one scientist says that their complex social behaviours tend to refute Manger's claim.