Researchers at the New York Aquarium installed mirrors so that they could be seen by two bottlenose dolphins and then tested to see if the animals were self-aware enough to look at the reflected image of markings on their bodies. Diana Reiss of Columbia University and Lori Marino of Emory University report today in the Proceedings of the National Academy of Sciences that both animals responded by looking long and hard at temporary ink marks placed on their face and sides. Mirror self-recognition in chimpanzees had been demonstrated in earlier studies when it was shown that the animals responded to body marks.
Humans learn to relate a mirrored image to themselves at an early age.
The ability suggests a self-awareness that some experts believe is reserved only for the higher primates. Attempts to demonstrate this ability have failed for other animals, including monkeys, lesser apes and elephants, the researchers report. But Reiss and Marino said that their experiment showed that chimpanzees and dolphins react in similar ways when investigating body marks that could be viewed only by a mirror. In the study, mirrors were placed in the dolphins' pools at the aquarium. The animals were then marked with a non-toxic ink and allowed to swim to the mirrors.