Wednesday, May 17, 2006

Dolphins have discovered "names" of the sort we use.

It has been known since the 1960s that dolphins develop individually distinctive signature whistles that they use to maintain group cohesion. Now Janik et al have shown that dolphins extract identity information from signature whistles even after all voice features have been removed from the signal. The synthesized whistles retained the distinct variation in frequency over time of an individual's signal, but removed other characteristics like harmonics, dynamics, and extraneous noises such as the clicking sounds that dolphins can also make. When exposed to the artificial whistle modeled after that of a related group member, other dolphins turned towards the sound. Excerpts from Henry Fountain's comments on this work in the New York Times: "To draw an analogy to humans, the frequency modulation pattern is the "language," and the dolphins could identify it regardless of the whistle's "voice." And a quote from Janik: "Most other animals appear to rely on the sound of the voice, rather than any coded information, for recognition. But parrots may have similar "signature" calls, which shows that you can do this if you have a huge brain, but you can also do this if you have a small one."

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