How Koko Mastered Sign Language and Learned to Communicate

“The Gorilla Foundation is sad to announce the passing of our beloved Koko,” the research center said of the iconic western lowland gorilla who mastered sign language. The foundation reported that Koko died at age 46. And the group added that Koko “touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy.”

Koko died in her sleep at the foundation’s preserve in California’s Santa Cruz Mountains. Throughout her life, she made headlines with her skills. She learned to communicate with humans through American Sign Language, took her own photo for the cover of National Geographic, and even befriended actor Robin Williams.

Koko and her Lifelong Teacher and Friend, Dr. Penny Patterson

Koko shares a flower with researcher Penny Patterson | The Gorilla Foundation

Koko was chosen for the language project as an infant

Fox News reports that Koko was born at the San Francisco Zoo. At birth, she received the name “Hanabiko,” Japanese for “fireworks child,” because she was born on the fourth of July in 1971, according to NPR. As an infant, she was chosen to work on a language project with psychologist Francine “Penny” Patterson at the zoo. Patterson began teaching Koko sign language, in an effort that became part of a Stanford University project in 1974.

She learned to sign 1,000 words

Koko demonstrated an extraordinary aptitude for language after Patterson began working with her. Fox News reports that in the course of her lifetime, Koko learned to sign 1,000 words in American Sign Language. (According to The Atlantic, that means that Koko had a vocabulary comparable to that of a 3-year-old human child.) She also learned to understand 2,000 words of spoken English. The Atlantic notes that researchers have made many attempts to teach human languages to animals. But none have been more successful than Patterson’s achievement with Koko.

Koko understood some English before Patterson started working with her

The Atlantic learned that according to Patterson, Koko already knew some English when the pair began working together. “She understood some English from the very beginning, because she was immersed in a language-speaking environment,” Patterson explained. “She also had some signs when I arrived that she used without anybody prompting her.” So Patterson taught Koko new signs and started asking her questions.

Gorillas use signs among themselves

Patterson explained that Koko isn’t the only gorilla to use some form of signs to communicate. In fact, gorillas often use signs to talk among themselves. She said that researchers have cataloged about 100 different signs in various studies of zoo gorillas. Gorillas even seem to have some innate gestures. Patterson saw a few such signs in the gestures shared by Koko and her brother, who had never met. And Patterson added that gorillas living in a zoo have “so much more to talk about” than gorillas living in the wild.

Koko would sometimes create signs on the spot

Patterson also told The Atlantic that Koko — and other gorillas — would sometimes create new signs on the spot, to communicate something in a specific situation. She created new signs for words that the researchers didn’t have signs for, like “barrette.” And she also created signs that were more difficult for them to figure out, like a sign she used to ask them to take off their lab coats. She would also communicate by tearing out a page of a magazine or a book to show the researchers something specific, and she would put out cards with objects printed on them in anticipation of symbolic events, like birthdays, holidays, and anniversaries.

She referred to herself as a ‘queen’

The Atlantic reports that one of the first words that Koko chose to refer to herself was the sign for queen. “The gorilla was only a few years old when she first made the gesture — sweeping a paw diagonally across her chest as if tracing a royal sash,” the publication notes. If Koko was a queen, her kingdom was the Gorilla Foundation’s sprawling research facility in the mountains outside Santa Cruz, California.

Koko appeared in several documentaries

Fox notes that Koko appeared in several documentaries, and twice in National Geographic, in 1978 and 1985. And Koko’s 1978 National Geographic cover featured a photo that she had taken of herself in a mirror. That cover was published in 1978, seven years after Koko began working with Patterson at the San Francisco Zoo. In 1985, the magazine profiled the relationship between Koko and her pet kitten: Koko and All Ball.

She made friends with Robin Williams

Koko also made friends with many humans, including actor Robin Williams. Fox reports that the pair bonded when Williams visited the Gorilla Foundation in 2001. Koko showed him around and insisted that he tickle her. They made faces at each other, and Koko seemed to recall seeing Williams in a movie, according to NPR. She also wanted to try on his glasses.”Robin’s ability to just ‘hang out’ with Koko, a gorilla, and in minutes become one of her closest friends, was extraordinary and unforgettable,” Patterson wrote at the time. Fox News notes that when Williams died of suicide in 2014, Koko was said to be particularly upset.

Koko showed the depth of her emotional life

NPR reports that Koko’s ability to interact with people made her an international celebrity. But Koko also revealed that she had a deep emotional life. She shared moments of happiness and sadness with not only Patterson, but also another researcher, Ron Cohn. When her cat, Ball, was hit by a car and died, she expressed her grief through sign language. When Patterson asked Koko, “What happened to Ball?” Koko formed the signs to say, “Cat, cry, have-sorry, Koko-love.” Then she paused and added two more signs to say, “Unattention, visit me.”

Read more: From Outsmarting Humans to Coping With Stress, These Are the Smartest Animals in the World

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