SAN DIEGO—Are dolphins as smart as people? And if so, shouldn't we be treating them a bit better than we do now? Those were the topics of discussion at a session on the ethical and policy implications of dolphin intelligence here today at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW).

First up, just how smart are dolphins? Researchers have been exploring the question for 3 decades, and the answer, it turns out, is pretty darn smart. In fact, according to panelist Lori Marino, an expert on cetacean neuroanatomy at Emory University in Atlanta, they may be Earth's second smartest creature (next to humans, of course).

Marino bases her argument on studies of the dolphin brain. Bottlenose dolphins have bigger brains than humans (1600 grams versus 1300 grams), and they have a brain-to-body-weight ratio greater than great apes do (but lower than humans). "They are the second most encephalized beings on the planet," says Marino.

But it's not just size that matters. Dolphins also have a very complex neocortex, the part of the brain responsible for problem-solving, self-awareness, and variety of other traits we associate with human intelligence. And researchers have found gangly neurons called Von Economo neurons, which in humans and apes have been linked to emotions, social cognition, and even theory of mind—the ability to sense what others are thinking. Overall, said Marino, "dolphin brains stack up quite well to human brains."

What dolphins do with their brains is also impressive. Cognitive psychologist Diana Reiss of Hunter College of the City University of New York brought the audience up to speed on the latest on dolphin behavior. Reiss has been working with dolphins in aquariums for most of her life, and she says their social intelligence rivals that of the great apes. They can recognize themselves in a mirror (a feat most animals fail at—and a sign of self-awareness). They can understand complex gesture "sentences" from humans. And they can learn to poke an underwater keyboard to request toys to play with. "Much of their learning is similar to what we see with young children," says Reiss.

So if dolphins are so similar to people, shouldn't we be treating them more like people? For example, should we really being keeping them captive in zoos and aquariums? "The very traits that make dolphins interesting to study," says Marino, "make confining them in captivity unethical." She notes, for example, that in the wild, dolphins have a home range of about 100 square kilometers. In captivity, they roam one-ten-thousandth of 1% of this.

Reiss is more concerned with the massive dolphin culling seen in some parts of the world. She showed graphic video of dolphins being drowned and stabbed as the waters turned red with blood in places such as the Japanese town of Taiji. Now that scientists know so much about how dolphins think and feel, she said, they should use that data to build a bridge to the public—a big theme of this year's meeting. "Our scientific knowledge needs to be used to influence international policy and ethical considerations," she said. "Scientific facts should transcend geographic boundaries."

Up last, Thomas White, a philosopher at Loyola Marymount University in Redondo Beach, California, made the argument that dolphins aren't merely like people—they may actually be people, or at least, "nonhuman persons," as he described them. Defining exactly what it means to be a person is difficult, White said, but dolphins seem to fit the checklist many philosophers agree on: They're alive, aware of their environment, and have emotions—those ones are easy. But they also seem to have personalities, exhibit self-controlled behavior, and treat others appropriately, even ethically. That combination of traits is harder to come by in the animal world. When it comes to what defines a person, said White, "dolphins fit the bill."

But before the researchers take their findings too far, experts caution that the scientific case for dolphin intelligence is based on relatively little data. "It's a pretty story, but it's very speculative," says Jacopo Annese, a neuroanatomist at the University of California, San Diego. Despite a long history of research, scientists still don't agree on the roots of intelligence in the human brain, he says. "We don't know, even in humans, what is the relationship between brain structure and function, let alone intelligence." Far less is known about dolphins, Annese says.

And who wants to be like humans anyway? As one audience member noted, our conflicts kill and displace millions of our own species. "When we try to think about how we treat these creatures," he said, "we should also think about how we treat ourselves."