By Rick Weiss
Elephants can recognize themselves in a mirror and use their reflections to explore hidden parts of themselves, a measure of subjective self-awareness that until now has been shown definitively only in humans and apes, researchers reported yesterday.
The findings confirm a long-standing suspicion among scientists that elephants, with their big brains, complex societies and reputation for helping ill herdmates, have a sufficiently developed sense of identity to pass the challenging "mirror self-recognition test."
The test, which in this case required construction of a huge, "elephant-proof" mirror at the Bronx Zoo, where the experiments were conducted, provides an index of an animal's ability to conceive of itself. It is a quality of self-consciousness that some scientists believe is a prerequisite for the emergence of empathy and altruism.
Such animals, the thinking goes, are in a position to use what they know about themselves to make inferences about other beings and their needs.
"It really is a clue about the evolution of intelligence," said Diana Reiss of the Wildlife Conservation Society in New York, who led the new study on the endangered species with Frans de Waal and Joshua Plotnik of the Yerkes National Primate Research Center in Atlanta.
"It tells us you can come to this same endpoint with very different creatures and with very different brains," said Reiss, who has seen similar but less certain signs of self-recognition among dolphins.
Gordon G. Gallup Jr., a psychology professor at the State University of New York at Albany who developed the mirror test nearly 40 years ago, praised the elephant study as a "very solid, very impressive piece of scientific work."
Some scientists took a more skeptical view, reflecting the controversy that has long engulfed the field of animal intelligence generally and the meaning of the mirror recognition test in particular.
"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. Dunbar criticized the Proceedings of the National Academy of Sciences, the journal that published the new results in its early online edition yesterday, for what he called "poor editorial standards."
Researchers over the years have provided body-size mirrors to hundreds of animals in zoos and other habitats. Almost always, the animals act as though the image they see is of another.
"Most animals seem incapable of learning that their behavior is the source of the behavior in the mirror," Gallup said. "They are incapable of deciphering that dualism."
By contrast, human babies get it by age 2, as do adult chimpanzees, bonobos and orangutans.
Monkeys, which are more distantly related to humans than are apes, never catch on. Indeed, the only non-ape species to come close to passing until now has been the bottlenose dolphin; it lacks the limbs to touch itself (a key part of the mirror test's final challenge) but can use mirrors to examine hidden parts of its body.
The new study involved three female Asian elephants at the zoo, in New York City. Workers built a 64-square-foot acrylic mirror, cemented it to plywood, framed it in steel and bolted it to a stone wall of the elephant enclosure.
"Our primary concern was the safety of the elephants," said Plotnik, a graduate student at Emory University, home to the Yerkes lab. "Our second concern was making sure they don't destroy the mirror. They are very curious animals."
In a series of experiments, the elephants first explored the mirror -- reaching behind it with their trunks, kneeling before it and even trying to climb it -- gathering clues that the mirror image was just that, an image.
That was followed by an eerie sequence in which the animals made slow, rhythmic movements while tracking their reflections. Then, like teenagers, they got hooked.
All three conducted oral self-exams. Maxine, a 35-year-old female, even used the tip of her trunk to get a better look inside her mouth. She also used her trunk to slowly pull her ear in front of the mirror so she could examine it -- "self-directed" behaviors the zookeepers had never seen before.
Moreover, one elephant, Happy, 34, passed the most difficult measure of self-recognition: the mark test. The researchers painted a white X on her left cheek, visible only in the mirror. Later, after moving in and out of view of the mirror, Happy stood directly before the reflective surface and touched the tip of her trunk to the mark repeatedly -- an act that, among other insights, requires an understanding that the mark is not on the mirror but on her body.
The researchers also placed a transparent, "sham" mark that could not be seen in the mirror on Happy's right cheek, to see if the feel of that mark on the skin alone might cause her to touch that spot. It did not.
DeWaal acknowledged that the precise meaning of the test is debatable. In particular, he said, "people who work on animals that don't pass the test get upset" and tend to belittle its meaning.
But he and many others strongly suspect that the rarity of mirror self-recognition -- along with it being more common among animals reported to help other animals in need -- makes the test a good marker for a certain level of consciousness.
"I believe that all animals have some level of self-awareness, but those that pass the mirror test have more of it," de Waal said.
Marc Hauser, a Harvard biologist who has studied self-recognition in cotton-top tamarins, said that the mirror test is valuable but that other tests can also shed light on "what kinds of thoughts animals have about themselves and others."
Monkeys do well on other tests of self-awareness, for example, including some that measure their awareness of gaps in their knowledge. "They're good at knowing what they don't know," Hauser said.
Some birds are especially good at knowing what other animals know about them: Jays will move hidden food if they realize another bird has been watching them hide it.
Whatever the mirror test's real meaning, the fact that few beyond humans can pass it speaks to the need to protect Asian elephants -- which are endangered due to hunting and habitat destruction -- and to continue the search for similarly endowed critters, Reiss said.
Among the leading candidates: orca, or "killer," whales, which are fearsome hunters but are also highly social and intelligent.
Shamu, is that you?