Large brain size does not necessarily mean that an animal is especially intelligent. A. Bottlenose dolphins have a high EQ, a measure of the ratio of brain mass to body mass that correlates with various cognitive abilities and possibly with life-history patterns in animals. B. The need to process high-frequency sounds for echolocation has been offered as an explanation for bottlenose dolphins' unusually large brains, but not all good echolocators have high EQs. C. The brain size of bottlenose dolphins is strongly correlated with the amount of cooperation and competition in relationships outside the mother-offspring relationship. D. Scientists are now using findings from their studies of bottlenose dolphins to determine the connection between the presence of a large brain and the potential for intelligence in other species. E. Bottlenose dolphins, like certain other large-brained animals, have complex social relationships, so their large, metabolically expensive brains may have evolved partly to permit complex social functioning. F. Biologists disagree about whether the larger-than-usual brain of the bottlenose dolphin makes it more intelligent or more metabolically efficient than other mammals with less brain mass.