Marine biologists at the University of St. Andrews studied a group of bottlenose dolphins in Sarasota Bay, Fla. and found that not only do the animals appear to convey information about themselves by their whistles, but they also seem to recognize each others' unique whistle. To make sure that the dolphins weren't simply identifying one another by the tone of the sounds, researchers played synthetic versions of the signature whistles of other dolphins through underwater loudspeakers. Many of the dolphins turned around more frequently when they heard the synthesized whistle of a relative than when they heard the call of an unrelated companion. They also tended to ignore the synthesized whistles of dolphins they did not know. Scientists believe this ability occurs in other species of dolphin as well, and names are assigned shortly after birth. What is perhaps most remarkable about this study, published in the May 12, 2006 issue of the Proceedings of the National Academy of Sciences, is it shows humans and dolphins share the characteristic of recognizing themselves as individuals with separate identities.