Herb Terrace, Columbia University

Nim Chimpsky gets a kiss on the cheek from one of his chimp-sitters.

"Project Nim," a documentary by Oscar-winning director James Marsh, is a heartwarming and heartbreaking story about a home-bred, pot-smoking, cookie-chomping chimpanzee called Nim Chimpsky. Nim was the star player in a controversial language experiment that failed ... but nevertheless laid the foundations for research into primate communication. 

In the early 1970s, Herb Terrace, a Columbia University psychologist, adopted a 2-week-old chimpanzee. Nim Chimpsky (named after linguist Noam Chomsky) was to be the star of an experiment to see if non-human animals could be taught the elements of language. At the time, linguists and psychologists were locked in a shouting match about the true nature of our chatty brains and the origins of human language. Terrace hoped Nim would end the raging debate about how and why human language evolved. 

The behaviorists led one camp, and said that language could be taught and learned by other intelligent, non-human species. The opposing camp, led by Chomsky, insisted that language was a human product and there were parts of it that non-human species could never ape. 

Terrace, who still does research on primate intelligence at Columbia, had heard stories about another precocious chimpanzee named Washoe, who lived with her scientist "parents" at the University of Nevada in Reno and had been taught to communicate through American Sign Language. 

But Terrace wasn’t satisfied with the way Washoe’s feats had been documented. Terrace wanted to raise young Nim among people, just as Washoe had been brought up, but scrupulously log his progress and learning abilities. If chimpanzees could in fact master elements of human language, he wanted to be sure how they did it, and how well they picked it up. "I wanted to have a total record of how Nim signed," Terrace told me.

Courtesy of "Project Nim"

It wasn't speech that Terrace was after: The vocal cords of chimpanzees weren't designed to replicate human speech. But if the behaviorists were correct, chimps, our nearest genetic relatives, should be able to learn and communicate using the grammatical rules and expressive elements that American Sign Language and spoken languages shared if they were brought up among people. 

So, at the age of 2 weeks, Nim Chimpsky was put in the foster care of Terrace's student, Stephanie LaFarge, who lived with her family in Manhattan. LaFarge, who even breast-fed Nim, would be the first of a string of chimp-sitters who tried to teach him American Sign Language. Laura-Ann Petitto, then an undergraduate at Columbia, would be next. She raised Nim from the time he was 3 months old until he was 4 years old. 

At first, the results were astonishing. Nim learned quickly, and his caretakers — Terrace's small army of students — carefully recorded reams of video and pages of notes describing Nim's signs and behavior. In all, Nim learned 120 words, and used them to communicate with thousands and thousands of phrases.

"[Other researchers used to say], this is like getting an SOS from out of space. And I felt the same way," Terrace told me. "How amazing would it be to ask a chimp how he felt about something?

Herb Terrace, Columbia University

The experimental data made it look as if Nim the "A" student had settled the matter: Human brains weren't that special when it came to language abilities. For a time, it seemed as though the behaviorists had a resounding victory on their hands.

Terrace was writing up his findings for the journal Science when one day, as he watched a well-worn tape of Nim signing with his teacher, he began to notice that something was off. “Then I realized the teachers were prompting him,” Terrace told me. “They weren’t even aware of this. But Nim was.” 

In a “quarter of a second,” years of observations came crashing down, Terrace told me. "My understanding of Nim signing the grammatical rule was wrong," he said. "Eventually I concluded that our minds are fundamentally different from a chimp's."

It had to do with our understanding of ourselves as individuals. "We’re aware of our mind," Terrace said. "With a chimpanzee, I don’t think there’s any awareness of one’s own mind and another mind out there. That means you can’t have any concept in a chimpanzee of a self and other." 

Nim used the concepts of “I” and “Nim” interchangeably. When he wanted cookies, Nim's second caretaker Petitto told me, the chimp would take Petitto’s hand and lead her to the kitchen, to the locked cabinet in which the cookies were stored. While his message was clear, Petitto said, Nim could never take himself out of the picture. “He took me through the motions. It was physical. He couldn’t say, 'On Monday could you buy the cookies,'" she explained. 

Susan Kuklin

Nim signing with Laura-Ann Petitto.

And the ability to take ourselves out of the situations we describe through language is one of the things that make humans unique as communicators. “Language frees us up from the here and now, [to] let you and I talk about Mars without leaving Earth,” Petitto says. 

Terrace eventually concluded that chimpanzees lacked the "social intelligence" that made humans able to talk to each other, and Project Nim was closed. Nim, now a full-grown hulk of a chimp, was shipped off to a center in Norman, Okla., to rub shoulders with other chimpanzees his own size. 

With that, Nim’s participation in science ended — unless you count his stint as a medical test subject. His Oklahoma caretakers covertly sold him to a cancer research facility, but the sale was exposed by the media. A legal challenge resulted in Nim's return to the sanctuary in Norman, an adventure that "Project Nim" describes in detail. 

Though scientists concluded that Nim did not use language to communicate independently, they also saw that this was no dumb animal. "[The Nim project] opened people up to the possibility of incredible intelligence that they hadn't suspected before," said Frans de Waal, a primate researcher at Emory University who studies the emotional bonds that chimpanzees have with each other. 

Bringing a chimpanzee home to teach it human language was all the rage once upon a time, but that’s old hat now, he said. Communication studies on chimp behavior now look at the many and varied ways in which chimps and other primates interact naturally. The Nim project was pivotal in giving scientists an early glimpse of those rich possibilities. “We feel like the language studies have opened up an enormous amount of knowledge about cognition, but not about linguistics,” de Waal said. 

De Waal is particularly interested in chimp communication through body language and gestures. It’s complex, involved and surprisingly similar to human gestural communication. “If you put young human children with chimpanzees, they make wonderful playmates,” de Waal told me. “They understand each other perfectly because their body language is the same — there’s an enormous similarity.” 

Chimps have also shown a deep capacity for empathy. When one family of chimps experiences a death, "other chimpanzees come over and comfort them," de Waal said. 

Laura-Ann Petitto, who was Nim's longest caregiver, still speaks gushingly about her emotional bond with Nim. “It’s unlike anything you’ve experienced," she told me. "It’s not like being with a child, it's not like being with a dog — [Nim] was his own category. So he pulled out of me emotions and thoughts that were unique to me, and very powerful, because he was unlike any category that we have." 

Harry Benson

"Project Nim," the documentary, opened in U.S. theaters on Friday.

Petitto said her experience with Nim deeply motivated and influenced her work on the human brain. "I know how the brain tissue changes over time. I can look inside a baby's brain at a couple of days old and I can understand if that baby is at risk for language disorders later in its life," she told me. "All of these gifts that I can give to our species have been fundamentally informed by my work through Nim. So there’s been a wonderful closed circle."

More recent research reveals that chimps may be more attuned to understand human speech than previously thought, even if they can’t communicate themselves. A study published last month in Current Biology reported that a chimp raised by humans, as Nim was, could understand distorted human speech sounds. Such findings highlight "the importance of early experience in shaping speech perception," the study’s lead author told BBC News. 

Though he does not work on language studies any more, Terrace continues to explore the intelligence and memory capacity of monkeys, studying how quickly and extensively they remember combinations and sequences of images and numbers. “I’ve been studying how good their memory is, and I found it’s fantastic,” Terrace says. “And, I can sort of relate that to the work I did with the chimp in that. These monkeys are much smarter than anybody thought. But that kind of smarts does not give you language.” 

More about animal communication:

• How to speak 'Avatar'
• Grow a new language in your head
• Humans wired for language at birth

Nidhi Subbaraman writes about science and technology at msnbc.com. Find her on Twitter and join our conversation on the Cosmic Log Facebook page.

To learn more about 'Project Nim,' check out the film's website. The film was based on the book, 'Project Nim: The Chimp Who Would Be Human,' by Elizabeth Hess.