What's going on in there? Presuming something akin to self-awareness is gaining social traction, if not hard evidence.

Creature Comforts

Who knows what Arturo the polar bear was thinking as he paced back and forth in the dark, air-conditioned chamber behind his artificial grotto? Just down the pathway Cecilia sat quietly in her cage, contemplating whatever chimpanzees contemplate.

In recent years, both creatures, inhabitants of the Mendoza Zoological Park in Argentina, have been targets of an international campaign challenging the morality of holding animals captive as living museum exhibits. The issue is not so much physical abuse as mental abuse — the effect confinement has on the inhabitants’ minds.

Last July, a few months after I visited the zoo, Arturo, promoted by animal rights activists as “the world’s saddest polar bear,” died of what his keepers said were complications of old age. (His mantle has now been bestowed on Pizza, a polar bear on display at a Chinese shopping mall.)

But Cecilia (the “loneliest chimp,” some sympathizers have called her) has been luckier, if luck is a concept a chimpanzee can understand.

In November, Judge María Alejandra Mauricio of the Third Court of Guarantees in Mendoza decreed that Cecilia is a “nonhuman person” — one that was being denied “the fundamental right” of all sentient beings “to be born, to live, grow, and die in the proper environment for their species.”

Agreeing to a petition by animal rights lawyers in Argentina for a writ of habeas corpus — a demand that a court rule on whether a prisoner or inmate is being legally detained — the judge ordered that the chimpanzee be freed from the zoo and transferred to a great ape sanctuary in Brazil.

In an earlier case, an appeals court in Buenos Aires upheld a judge’s demand that the city zoo provide an orangutan named Sandra with a way of life consistent with her “well-being, behavioral complexity, and emotional states.”

Argentine law applies, of course, only in Argentina. But the decisions in the two cases have been taken as encouragement by activists in other countries. In the United States, the Nonhuman Rights Project has been trying for years — so far unsuccessfully — to use habeas corpus to free captive chimpanzees from labs and private zoos and have them declared nonhuman persons.

In the legal realm, a creature doesn’t necessarily have to be highly intelligent or even aware of its own existence to be recognized as a person — an entity with certain rights under the law. Corporations have been deemed “juridical persons,” and last year in New Zealand, a river revered by the Maori was declared a person, meaning that lawsuits can be filed (by people) on the river’s behalf.

But this is more than a matter of legal abstractions. No one would be fighting these battles if they didn’t believe that great apes are highly intelligent, introspective creatures experiencing some kind of inner life.

Driven by our own ability to analogize and abstract, we seek clues of conscious behavior in other species. Visual: iStock.com

Though the science is far from settled, and probably will never be, the idea that something resembling a subjective, contemplative mind exists in other animals has become mainstream — and not just for apes. Recent popular science books include “What a Fish Knows: The Inner Lives of Our Underwater Cousins,” “The Soul of an Octopus: A Surprising Exploration Into the Wonder of Consciousness” and “Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness.”

A paper published last spring in the Proceedings of the National Academy of Sciences proposed that insects have neurological structures that may allow them to experience some kind of subjective feelings — the rudiments of a first-person perspective on the world. In “The Ancient Origins of Consciousness: How the Brain Created Experience,” Todd E. Feinberg and Jon M. Mallatt attempt to trace these anatomical clues of an inner life all the way back to the Cambrian explosion, more than half a billion years ago, when multicellular creatures — ancestors to modern animals — appeared on Earth.

The vision is of a continuum of consciousness reaching back through evolutionary time, like fins evolving to form legs, arms, feet, and hands with opposable thumbs. But no one really knows. When the objective eye of science is trained on the question of subjectivity, the evidence is always indirect and inevitably in dispute.

Some scientists propose that consciousness arose abruptly when brains, which happened to be human brains, reached a critical level of neurological complexity. Along with this evolutionary leap came language rich enough to express endlessly intricate ideas. The result was a species, unique on the planet, that is not only aware, but aware it is aware. That thinks and thinks about thinking.

By some measures, we share 99 percent of our DNA with chimpanzees. But that extra 1 percent may be crucial — extra loops of neurological wetware that give rise to the primate that calls itself Homo sapiens. Unlike the proverbial monkeys randomly typing Shakespeare, we know which keys we want to press on the typewriter, scrolling out documents and legal systems with ideas like habeas corpus and personhood.

Looking beyond the anatomical evidence, behavioral research can go only so far in illuminating the mystery. In well-known studies, chimpanzees have been trained to use simplified sign language, plastic tokens, or symbols on a keyboard for what seems like rudimentary communication. In the wild, yipping prairie dogs and dancing bees have been shown to engage in surprisingly complex signaling.

But signaling is not the same as language, and intelligence doesn’t automatically imply consciousness. The reason most of us don’t seriously believe that everyone else is a zombie is that we can share the subtleties of our inner worlds through language. Solipsists can discuss solipsism with other solipsists.

A paper published last fall in Science reported new evidence that great apes have what psychologists call a theory of mind — that they can infer another creature’s intentions from its behavior and act accordingly. That trait has also been attributed to ravens.

Other experiments indicate that great apes, dolphins, and elephants can recognize themselves in a mirror. A new paper in Proceedings of the National Academy of Sciences finds signs of mirror recognition in rhesus monkeys.

But studies like these can only cut so deep. Does the simian wonder why the reflection is like the one in a cup of water? Does it pick up the mirror and try to drink it? Does it puzzle over why, in the reflected world, left is reversed with right? Does it contemplate the past and imagine the future and know that one day it will die? For all of our advances in brain scanning and other neurological techniques, we’re stuck on the outside looking in.

Some philosophers, like Daniel Dennett, have suggested that consciousness is something that only appears collectively within a culture, where ideas clash with ideas, fracturing and combining into theories and ideologies. Evolution by genes gives way to evolution by memes.

Maybe this is just a matter of degree. Primatologists see hints of what they consider simian culture. Tribes of chimpanzees living in the wild use different methods to get honey from a log. One group uses sticks while another uses leaves — like chopsticks instead of knives and forks.

Locked into a debate with no foreseeable conclusion, what seems to be evolving in human culture is a sense of humbleness and a willingness to give other creatures the benefit of the doubt. Bowing to the pressure from activists, both the Buenos Aires and Mendoza zoos closed last year and have begun converting themselves into what are called in Spanish “ecoparques,” centers devoted to education and wildlife conservation. Many of the animals will be freed to preserves where they will no longer exist for the primary purpose of being on display.

“Animals and great apes are not objects to be exposed like a work of art created by humans,” Judge Mauricio wrote in her decision, which included quotes from Immanuel Kant, Anatole France, Buddha, and Gandhi. In agreeing to act on behalf of Cecilia, she suggested that we’re doing it for ourselves, as an expression of our humanity.

“I am convinced that if the community is duly informed and educated about the circumstances that result in my decision, it will feel the satisfaction of knowing that acting collectively as a society we have been able to give Cecilia the life she deserves,” Mauricio wrote.

“Cecilia’s present situation moves us,” she continued. “If we take care of her well​-being, it is not Cecilia who will owe us; it is us who will have to thank her for giving us the opportunity to grow as a group and to feel a little more human.”

George Johnson is the author of “The Cancer Chronicles,” “The Ten Most Beautiful Experiments,” and seven other books, which have been translated into 15 languages. His column, “Raw Data,” appears in The New York Times.