Washoe, a female chimpanzee said to be the first non-human to acquire human language, has died of natural causes at the U.S. research institute where she was kept.

Washoe was said by her keepers to have a vocabulary of about 250 words. Critics contended she had only learned to imitate sign language.
(Central Washington University/Associated Press)

Washoe, who first learned a bit of American Sign Language in a research project in Nevada, had been living on Central Washington University's Ellensburg campus since 1980. Her keepers said she had a vocabulary of about 250 words, although critics contended Washoe and some other primates learned to imitate sign language, but did not develop true language skills.

She died Tuesday night, according to Roger and Deborah Fouts, co-founders of the Chimpanzee and Human Communications Institute on the campus. She was born in Africa in about 1965.

"Washoe was an emissary, bringing us a message of respect for nature," Mary Lee Jensvold, the assistant director of the nonprofit institute, said Wednesday.

Washoe was taken to the veterinary hospital at Washington State University for a necropsy. Her memorial will be Nov. 12.

The Fouts went to Central Washington from Oklahoma in 1980 to create a home for Washoe and other chimps.

Washoe also taught sign language to three younger chimps who remain at the institute, Central Washington spokeswoman Becky Watson said. They are Tatu, 31, Loulis, 29, and Dar, 31.

"The entire CWU community and the Ellensburg community are feeling the loss of our friend, Washoe, one of our daughters," said CWU president Jerilyn S. McIntyre.

Washoe was the only chimpanzee at the institute born in Africa and was the matriarch of the chimpanzee family. She was named for Washoe County, Nev., where she lived with Allen and Beatrix Gardner of the University of Nevada, Reno, from 1966 to 1970.

Primate researcher Jane Goodall, in Roger Fouts' book Next of Kin, noted the importance of the work with Washoe.

"Roger, through his ongoing conversations with Washoe and her extended family, has opened a window into the cognitive workings of a chimpanzee's mind that adds new dimension to our understanding," Goodall was quoted as saying.

In 1967, the Gardners established Project Washoe to teach the chimp ASL. Previous attempts to teach chimpanzees to imitate vocal languages had failed. Roger Fouts was a graduate student of the Gardners.

For Washoe to be considered "reliable" on a sign, it had to be seen by three different observers in three separate instances. Then it had to be seen 15 days in a row to be added to her sign list.

The Gardners tried to make Washoe's environment as similar as they could to what a human infant with deaf parents would experience. Researchers communicated with Washoe by sign language, minimizing the use of spoken words.

The Gardners said that, for example, when Washoe entered their bathroom, she made the sign for "toothbrush" when she saw one.

But there was controversy over whether the chimp was really using ASL. Among those who doubted that chimps could use language were MIT linguist Noam Chomsky and Harvard scientist Steven Pinker.

Chomsky contended that the neural requirements for language developed in humans after the evolutionary split between humans and other primates. Pinker argued that primates simply learn to perform certain acts in order to receive rewards, and do not acquire true language.