Abstract
Cetaceans, including whales, dolphins, and porpoises, are mammals that live in aquatic environments far different from those of our terrestrial world. Recent studies have revealed that cetaceans have complex societies and cognitive abilities, comparable to those of “rational” terrestrial animals such as apes and humans. The positive correlation between relative brain sizes and group sizes in odontocetes apparently supports the social-brain hypothesis. In this paper, some recent cognitive studies, including those on tool use, object play, self-recognition, theory of mind (including false-belief task and joint attention), and complex social systems (which require higher cognitive ability), are reviewed to compare the cognitive abilities of cetaceans to those of other members of the “cognitive triangle,” including primates and corvids.
