Do Dolphins Have a Sense of Self?
Research suggests that dolphins, like humans, chimps and orangutans, perceive themselves as individuals
02-01-2003 // Michael Tennesen
PHOENIX, a 24-year-old bottlenose dolphin, swims to the side of an outdoor tank at the University of Hawaii's Kewalo Basin Marine Mammal Laboratory, her eyes trained on a young woman standing at the edge. Perched on a wooden platform above, Lou Herman, the slim, gray-haired director of the facility, signals the student to begin the experiment. She makes a series of hand gestures instructing Phoenix to perform one of five behaviors: jump over a long foam cylinder, swim under the cylinder, touch her pectoral fin to it, touch her tail to it or mouth it. She then signals the animal to either repeat the last thing she did or repeat anything but the last thing she did. To pass the test, Phoenix must be aware of herself as a distinct entity, remember her last behavior and use that memory to select her next behavior. On this day, Herman's staff tests the dolphin 33 times. Phoenix makes a mistake just once. "She's only human," he jests.
Herman 's experiment is one of several recent studies providing evidence that dolphins are capable of self-awareness, an attribute previously attributed only to humans and great apes. In humans, it first appears around the age of 18 to 24 months, when children begin to use the personal pronouns "I," "he," "she" and "it." Though some scientists are skeptical that the new work proves dolphins are self aware, Herman, a University of Hawaii psychologist who has studied dolphin intelligence for more than 20 years, is convinced by results of his own work. In his latest study, he taught a dolphin gestural "names" for nine different body parts; she then was able display each part—by touching or shaking it, for instance. "Dolphins could not do this," maintains Herman, "unless they had a sense of their own bodies and actions."
Further evidence comes from Diana Reiss, a psychobiologist at the Wildlife Conservation Society's Osborn Laboratories for Marine Science at the New York Aquarium, who discovered that bottlenose dolphins can recognize themselves in mirrors. In her experiments, she and her colleagues marked dolphins with temporary black ink on parts of their bodies the animals could see only by using a mirror. While unmarked dolphins ignored the mirror, "marked dolphins made a bee-line to it to see where they'd been marked," says Reiss. And after they'd been marked once, animals returned to the mirror to inspect themselves even when marked only with clear water.
Mirror self-recognition tests were developed in the 1970s by Gordon Gallup, a professor of psychology at the State University of New York in Albany. In his research, Gallup marked five chimpanzees with dye on their heads. When all five subsequently looked in a mirror, they would reach up and touch the marks, then look at and smell their fingertips. "Animals that can recognize themselves in mirrors can conceive of themselves," says Gallup. Until now, only chimpanzees and orang-utans had passed the mirror test. Elephants, monkeys and African gray parrots appear to use mirrors to find hidden objects but not to examine themselves. Other species ignore their own images or react to them, often aggressively, as if they are seeing other animals.
To Reiss and other researchers, the most fascinating implication of the new work is that self-awareness seems to have evolved independently in two different kinds of creatures with different brain structures—a phenomenon known as convergent evolution. "A dolphin is not a chimp," says Reiss. "It's not even a distant cousin. Humans separated from dolphins over 90 million years ago."
But why would self-awareness have evolved in dolphins? According to Gallup, the capability may give these highly social mammals an advantage when they interact with one another, including competition for mates. "Self-awareness," he says, "provides the ability to contemplate the past, to project into the future, and to speculate on what others are thinking." Herman suspects that self-awareness also helps dolphins hunt—by being able to distinguish prey from themselves and then predict how the fish will respond.
No matter why it evolved, researchers who study dolphins agree that mounting evidence for self-awareness provides one more reason for humans to stop killing the animals. Says Ken Martin, a senior scientist at Earthtrust in Hawaii, "We should have zero tolerance for dolphin kills by tuna fishermen rather than the 5,000 deaths a year the law currently allows."
California writer Michael Tennesen visited with dolphin scientists for this article.
