Elephants and other animals are thought to be in a unique position to use what they know about themselves to make inferences. Those inferences -- about other beings and about their own needs -- may give researchers clues about how intelligence is formed. "It really is a clue about the evolution of intelligence," said Diana Reiss of the Wildlife Conservation Society in New York.
In the recent elephant study, one elephant -- Happy, who is 34 -- passed the most difficult measure of self-recognition: the mark test. Researchers painted a white X on Happy's left cheek that was visible only in the mirror. Happy then stood before the reflective surface and touched the tip of her trunk to the mark repeatedly. This act confirmed her understanding that the mark is not on the mirror, but on her body.
Reiss led the new study on the endangered species with Frans de Waal and Joshua Plotnik of the Yerkes National Primate Research Center in Atlanta. The study has already been called a "very impressive piece of scientific work" by Gordon Gallup, a psychology professor at the State University of New York at Albany. Gallup developed the mirror test nearly 40 years ago.
However, some scientists took a more skeptical view of the recent elephant research. "Far too much has been made of a very trivial task in all these mirror experiments, and it has lately reached some dizzyingly bizarre heights," said Robin Dunbar of the University of Liverpool in England.
Over the years, researchers have used body-sized mirrors in front of hundreds of animals contained in zoos and other habitats. Gallup has said that "Most animals seem incapable of learning that their behavior is the source of the behavior in the mirror." Human babies, on the other hand, recognize this by the time they are two years old.
Additionally, adult chimpanzees and orangutans also learn from this mirror technique. Monkeys -- more distantly related to humans than are apes -- have never seemed to catch on, though. The only non-ape species to come close to passing the "mirror test" until now has been the bottlenose dolphin.