ATLANTA -- Elephants have joined a small, elite group of species-including humans, great apes and dolphins-that have the ability to recognize themselves in the mirror, according to a new finding by researchers at the Yerkes National Primate Research Center, Emory University, and the Wildlife Conservation Society (WCS) in New York. This newly found presence of mirror self-recognition in elephants, previously predicted due to their well-known social complexity, is thought to relate to empathetic tendencies and the ability to distinguish oneself from others, a characteristic that evolved independently in several branches of animals, including primates such as humans.
This collaborative study by Yerkes researchers Joshua Plotnik and Frans de Waal, PhD, director of Yerkes' Living Links Center, and WCS researcher Diana Reiss, PhD, published in the early online edition of the current issue of Proceedings of the National Academy of Sciences of the United States of America, was conducted as part of a wide array of cognitive and behavioral evolution research topics at Yerkes' Living Links Center.
"We see highly complex behaviors such as self awareness and self-other distinction in intelligent animals with well established social systems," said Plotnik. "The social complexity of the elephant, its well-known altruistic behavior and, of course, its huge brain, made the elephant a logical candidate species for testing in front of a mirror."
In the study, researchers exposed three female elephants housed at the Bronx Zoo in New York to a jumbo-sized mirror measuring eight feet high by eight feet wide inside the elephants' yard. During the exposure, the elephants tested their mirrored images by making repetitive body movements and using the mirror to inspect themselves, such as by moving their trunks to inspect the insides of their mouths, a part of the body they usually cannot see. Further, the animals did not react socially to their images, as many animals do, and did not seem to mistake their reflection for that of another elephant.
"Elephants have been tested in front of mirrors before, but previous studies used relatively small mirrors kept out of the elephants' reach," said Plotnik. "This study is the first to test the animals in front of a huge mirror they could touch, rub against and try to look behind."
One elephant also passed a standard test known as the mark test. Each elephant was marked with visible paint on its forehead-a place it could not see without a mirror-and also received a sham mark of colorless face paint. The sham mark controlled for tactile and odor cues to ensure touching the visible mark was due to seeing its reflection and not to the feel or smell of the paint. This test produced the same results as when great apes and human children are presented with the mark test.
"As a result of this study, the elephant now joins a cognitive elite among animals commensurate with its well-known complex social life and high level of intelligence," said de Waal. "Although elephants are far more distantly related to us than the great apes, they seem to have evolved similar social and cognitive capacities making complex social systems and intelligence part of this picture. These parallels between humans and elephants suggest a convergent cognitive evolution possibly related to complex sociality and cooperation."
Scientists have tested mirror self-recognition in a variety of animals other than humans and great apes, but invariably failed, with the exception of the bottlenose dolphin. "After the recent discovery that dolphins are capable of recognizing themselves in the mirror, elephants seemed the next logical species for testing," said Reiss. "Humans, great apes, dolphins and elephants, well known for their superior intelligence and complex social systems, are thought to possess the highest forms of empathy and altruism in the animal kingdom."
Further research on elephant cognition will be conducted by Yerkes' Living Links Center to explore topics in behavioral and cognitive evolution, specifically social complexity in Asian elephants, including cooperation and conflict resolution.
For more than seven decades, the Yerkes National Primate Research Center of Emory University has been dedicated to advancing scientific understanding of primate biology, behavior, veterinary care and conservation, and to improving human health and well-being. Today, the center, as one of only eight National Institutes of Health-funded national primate research centers, provides specialized scientific resources, expertise and training opportunities.
Recognized as a multidisciplinary research institute, the Yerkes Research Center is making landmark discoveries in the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems. Research programs are seeking ways to: develop vaccines for AIDS and malaria; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Parkinson's and Alzheimer's; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary links between biology and behavior.
Proceedings of the National Academy of Sciences